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The first total synthesis of bipenicilisorin (1) isolated from Penicillium chrysogenum SCSIO 41001 via its monomer natural product, penicilisorin (2), was achieved. Penicilisorin was synthesized in four steps from a o-bromobenzaldehyde derivative via the Pd-catalyzed one-pot fluorocarbonylation/lactonization/β-elimination cascade reaction. Iodination of penicilisorin gave 7-iodopenicilisorin which was dimerized by Pd-catalyzed homodimerization to provide (±)-bipenicilisorin. The unknown absolute configuration of naturally occurring (+)-bipenicilisorin was examined by optical resolution of the (±)-synthetic bipenicilisorin and a comparison of experimental and theoretical electronic circular dichroism (ECD) spectra. These results support the absolute configuration of the natural product to be Sa. A cytotoxic activity test of (+)-and (-)-bipenicilisorin using A549 cells revealed that (+)-1 has a lower IC50 value than (-)-1.

DOI： 10.1021/acs.jnatprod.4c00114

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Kagimminols A (1) and B (2), new cembrene-type diterpenoids, were isolated from an Okeania sp. marine cyanobacterium. By combining DP4 analysis with an efficient NMR chemical shift calculation protocol, we clarified the relative configurations of 1 and 2 without consuming precious natural products. We determined the absolute configurations by a comparison of theoretical electronic circular dichroism (ECD) spectra with experimental spectra, and the absolute configuration of 1 was verified experimentally. Finally, we found that 1 and 2 showed selective growth-inhibitory activity against the causative agent of human African trypanosomiasis. This study exemplifies that computational chemistry is an efficient tool for clarifying the configurations of natural products possessing tautomers in equilibrium.

DOI： 10.1021/acs.jnatprod.4c00056

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A healthy ocean is essential for human health, and yet the links between the ocean and human health are often overlooked. By providing new medicines, technologies, energy, foods, recreation, and inspiration, the ocean has the potential to enhance human health and wellbeing. However, climate change, pollution, biodiversity loss, and inequity threaten both ocean and human health. Sustainable realisation of the ocean's health benefits will require overcoming these challenges through equitable partnerships, enforcement of laws and treaties, robust monitoring, and use of metrics that assess both the ocean's natural capital and human wellbeing. Achieving this will require an explicit focus on human rights, equity, sustainability, and social justice. In addition to highlighting the potential unique role of the healthcare sector, we offer science-based recommendations to protect both ocean health and human health, and we highlight the unique potential of the healthcare sector tolead this effort.

DOI： 10.5334/aogh.4471

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Polycavernoside E (1), a new polycavernoside analog, was isolated from a marine Okeania sp. cyanobacterium. The relative configuration was elucidated primarily by analyzing the two dimensional nuclear magnetism resonance (2D NMR) data. The absolute configuration was clarified by comparing the electronic circular dichroism (ECD) data of 1 with those of known analogs. Polycavernoside E (1) exhibited moderate antitrypanosomal activity against Trypanosoma brucei rhodesiense. Furthermore, the isolation of polycavernoside E (1) from marine cyanobacteria provides additional evidence that marine cyanobacteria, and not red algae, are responsible for the biosynthesis of polycavernosides.

DOI： 10.3762/bjoc.20.57

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Akunolides A (1), B (2), C (3), and D (4), new macrolide glycosides, were isolated from a marine Okeania sp. cyanobacterium. Their structures were elucidated by spectroscopic analyses and derivatization reactions. Akunolides A-D (1-4) are classified as 16-membered macrolide glycosides, which are relatively rare structures for marine cyanobacterium-derived natural products. Akunolides A-D (1-4) showed moderate antitrypanosomal activities against Trypanosoma brucei rhodesiense, with IC50 values ranging from 11 to 14 μM. Furthermore, akunolides A (1) and C (3) exhibited no cytotoxicity against normal human WI-38 cells even at a concentration of 150 μM.

DOI： 10.1021/acs.jnatprod.3c00742

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Ikoamide (1) is a highly N-methylated antimalarial lipopeptide that was isolated from a marine cyanobacterium, an Okeania sp. in 2018, which shows strong antimalarial activity without cytotoxicity against human cancer cell lines. To establish a synthetic method for obtaining enough ikoamide for its biological evaluations, we have established a total synthesis of ikoamide. The synthetic method presented here lays the foundation for the development of novel ikoamide analogues, which may lead to a discovery of pharmaceutically unique antimalarial drug leads.

DOI： 10.1021/acs.joc.3c00595

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The linear lipopeptides okeaniamide A (1) and okeaniamide B (2) were isolated from an Okeania sp. marine cyanobacterium collected in Okinawa. The structures of these compounds were established by spectroscopic analyses, and the absolute configurations were elucidated based on a combination of chemical degradations, Marfey's analysis, and derivatization reactions. Okeaniamide A (1) and okeaniamide B (2) dose-dependently promoted the differentiation of mouse 3T3-L1 preadipocytes in the presence of insulin.

DOI： 10.1021/acs.jnatprod.3c00256

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Two new natural products were isolated from the marine cyanobacterium Rivularia sp. collected in Japan. Hennaminal possesses a very rare functional group, β,β-diamino unsaturated ketone, which has only been found in bohemamine-type natural products so far. Hennamide possesses a reactive N-acyl pyrrolinone moiety, which induces self-dimerization. The isolation and structure determination supported by computational chemistry and total synthesis, as well as the antitrypanosomal activities of hennaminal and hennamide are described.

DOI： 10.1021/acs.orglett.3c00421

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Polygonum chinense Linn. is a medicinal and invasive plant that belongs to the family Polygonaceae. The pharmacological activities and phytochemical constituents of Polygonum chinense are well reported, but the allelopathic effects and potent allelopathic substances of P. chinense remain to be investigated. Hence, this experiment was conducted to separate and characterize potentially allelopathic substances from an extract of the Polygonum chinense plant. The Polygonum chinense plant extracts highly suppressed the growth of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crusgalli (L.) P. Beauv.), and timothy grass (Phleum pratense L.) seedlings in a species- and concentration-dependent way. Two active substances were separated using a series of purification procedures and determined through spectral analysis as (−)-3-hydroxy-β-ionone and (−)-3-hydroxy-7,8-dihydro-β-ionone. These two compounds significantly suppressed the seedling growth of Lepidium sativum (cress) at concentrations of 0.01 and 1 mM, respectively. The extract concentrations necessary for 50% growth inhibition (I50 values) of the cress hypocotyls and roots were 0.05 and 0.07 mM for (−)-3-hydroxy-β-ionone, respectively, and 0.42 and 1.29 mM for (−)-3-hydroxy-7,8-β-ionone, respectively. These findings suggest that these two compounds are in charge of the inhibitory effects of the Polygonum chinense extract and may serve as weed control agents.

DOI： 10.3390/plants12071577

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Lyngbyapeptin B is a hybrid polyketide-nonribosomal peptide isolated from particular marine cyanobacteria. In this report, we carried out genome sequence analysis of a producer cyanobacterium Moorena bouillonii to understand the biosynthetic mechanisms that generate the unique structural features of lyngbyapeptin B, including the (E)-3-methoxy-2-butenoyl starter unit and the C-terminal thiazole moiety. We identified a putative lyngbyapeptin B biosynthetic (lynB) gene cluster comprising nine open reading frames that include two polyketide synthases (PKSs: LynB1 and LynB2), four nonribosomal peptide synthetases (NRPSs: LynB3, LynB4, LynB5, and LynB6), a putative nonheme diiron oxygenase (LynB7), a type II thioesterase (LynB8), and a hypothetical protein (LynB9). In vitro enzymatic analysis of LynB2 with methyltransferase (MT) and acyl carrier protein (ACP) domains revealed that the LynB2 MT domain (LynB2-MT) catalyzes O-methylation of the acetoacetyl-LynB2 ACP domain (LynB2-ACP) to yield (E)-3-methoxy-2-butenoyl-LynB2-ACP. In addition, in vitro enzymatic analysis of LynB7 revealed that LynB7 catalyzes the oxidative decarboxylation of (4R)-2-methyl-2-thiazoline-4-carboxylic acid to yield 2-methylthiazole in the presence of Fe2+ and molecular oxygen. This result indicates that LynB7 is responsible for the last post-NRPS modification to give the C-terminal thiazole moiety in lyngbyapeptin B biosynthesis. Overall, we identified and characterized a new marine cyanobacterial hybrid PKS-NRPS biosynthetic gene cluster for lyngbyapeptin B production, revealing two unique enzymatic logics.

DOI： 10.1021/acschembio.3c00011

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Caldorazole (1) is a novel polyketide that was isolated from a marine cyanobacterium in 2022. It is a unique natural product that exhibits potent inhibitory activity against mitochondrial respiratory chain complex I despite having no chiral centers. To establish a method for obtaining caldorazole without relying on biological resources and for constructing a useful synthetic route for studies of its structure-activity relationship, we achieved the first total synthesis of caldorazole using a convergent synthetic route.

DOI： 10.1021/acs.joc.2c03007

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Osmanthus fragrans Lour. has been cultivated for more than 2500 years because of the fragrance and color of the flowers. The flowers and roots have been used in tea, liquors, foods, and traditional Chinese medicine. The species contains more than 180 compounds including terpenoids, phenylpropanoids, polyphenols, flavonoids, and sterols. However, there has been limited information available on the allelopathic properties and allelopathic substances of O. fragrans. We investigated the allelopathy and allelopathic substances of O. fragrans and Osmanthus heterophyllus (G.Don) P.S. Green, as well as Osmanthus × fortunei Carrière, which is the hybrid species between O. fragrans and O. heterophyllus. The leaf extracts of O. fragrans, O. heterophyllus, and O. × fortunei suppressed the growth of cress (Lepidium sativum L.), alfalfa (Medicago sativa L.), Lolium multiflorum Lam., and Vulpia myuros (L.) C.C.Gmel with the extract concentration dependently. The extract of the hybrid species O. × fortune was the most active among the extracts. The main allelopathic substances of O. × fortunei and O. fragrans were isolated and identified as (+)-pinoresinol and 10-acetoxyligustroside, respectively. (+)-Pinoresinol was also found in the fallen leaves of O. × fortunei. Both compounds showed an allelopathic activity on the growth of cress and L. multiflorum. On the other hand, several allelopathic substances including (+)-pinoresinol may be involved in the allelopathy of O. heterophyllus. O. fragrans, O. heterophyllus, and O. × fortunei are evergreen trees. but their senescent leaves fall and cover the soil under the trees. It is possible that those allelopathic substances are liberated through the decomposition process of the leaves into their rhizosphere soil, and that they accumulate in the soil and provide a competitive advantage to the species through the inhibition of the growth of the neighboring competing plants. Therefore, the leaves of these Osmanthus species are allelopathic and potentially useful for weed management options in some agriculture settings to reduce commercial herbicide dependency for the developing sustainable agriculture systems.

DOI： 10.3390/plants12020376

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The phytotoxic potential of plants and the effect of their active components on another plant species is being explored as a potential alternative to synthetic herbicides for weed control. In the current study, we investigated the phytotoxic potential of the leaves of Dregea volubilis (L.f.) Benth. ex Hook.f. against four test plants [timothy (Phleum pratense L.), barnyard grass (Echinochloa crus-galli (L.) P. Beauv), lettuce (Lactuca sativa L.), and alfalfa (Medicago sativa L.)] and observed significant growth inhibition on those plants at concentrations >3 mg D.W. equivalent extract mL−1. A bioassay-governed purification of the D. volubilis extracts using different chromatography phases produced two growth inhibitory compounds, 3-hydroxy-α-ionone (compound 1) and 5-hydroxy-3,4-dimethyl-5-pentylfuran-2(5H)-one (compound 2). The compounds retarded the growth of barnyard grass and cress (Lepidium sativum L.) with I50 (concentration required for 50% growth suppression) values ranging from 0.098 to 0.450 mM for 3-hydroxy-α-ionone and 0.029 to 0.420 mM for 5-hydroxy-3,4-dimethyl-5-pentylfuran-2(5H)-one. Thus, the extracts and identified compounds may have the possibility to be utilized as bioagents for weed control.

DOI： 10.3390/agriculture12111826

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The plant Plumbago rosea Linn., belonging to the Plumbaginaceae family, is an important medicinal herb distributed in part of Southeast Asia, and there are many reports of its pharmacological properties. However, the allelopathic activities of P. rosea have not been examined. Thus, the present study was conducted to assess the allelopathic activity of P. rosea and to identify its allelopathic substances. The aqueous methanol stem extract of P. rosea significantly suppressed the seedling growth of barnyard grass (Echinochloa crus-galli L. P. Beauv.), Italian ryegrass (Lolium multiflorum Lam.), timothy (Phleum pretense L.), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), and alfalfa (Medicago sativa L.). The extract of P. rosea was then purified through chromatographic steps, and two active substances were isolated and determined as 7,4′,5′-tri-O-methyl dihydroquercetin and 7,4′,5′-tri-O-methylampelopsin. The two compounds significantly inhibited the seedling growth of cress, with 7,4′,5′-tri-O-methylampelopsin showing a greater inhibitory effect than 7,4′,5′-tri-O-methyl dihydroquercetin. This result may be due to the 3′-OH group in 7,4′,5′-tri-O-methylampelopsin. The effective concentrations of both compounds required for 50% growth inhibition (EC50 values) of cress seedlings were 0.24 mM and 0.59 mM for root and shoot, and 0.07 mM and 0.21 mM, respectively. These findings suggest that the two compounds may contribute to the allelopathic effect of P. rosea and could be used as a natural source of allelopathic substances.

DOI： 10.3390/agronomy12092020

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Phytotoxic substances in plants that may serve as alternative natural herbicides for controlling weeds are required for sustainable agriculture. We explored the phytotoxic activities of aqueous methanol extracts of Senna garrettiana (Craib) Irwin & Barneby leaves and the active substances they contain. The results revealed that the S. garrettiana leaf extracts had significant phytotoxic effects on three dicotyledons (Lepidium sativum L., Lactuca sativa L., and Medicago sativa L.) and two monocotyledons (Phleum pratense L. and Lolium multiflorum Lam.). An bioassay-guided isolation process yielded three active substances; caffeic acid, methyl caffeate, and (S)-6-hydroxymellein inhibited the seed germination, seedling growth, and biomass accumulation of L. sativum in a concentration-dependent manner. Based on the concentration required for 50% growth inhibition (IC50), (S)-6-hydroxymellein had the highest inhibitory effects on L. sativum in all test parameters, followed by methyl caffeate and caffeic acid. The L. sativum roots were the most susceptible to (S)-6-hydroxymellein (IC50 = 383 µM) and caffeic acid (IC50 = 2627 µM), whereas methyl caffeate (IC50 = 1361 µM) had the greatest effect on the L. sativum shoots. Thus, three isolated compounds may explain the phytotoxic effects of the S. garrettiana extracts. Consequently, caffeic acid, methyl caffeate, and (S)-6-hydroxymellein could be potential candidates for the future production of bioherbicides.

DOI： 10.3390/agriculture12091338

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Medicinal plants are rich sources of bioactive substances that can be used to develop environmentally friendly weed control alternatives. Marsdenia tenacissima (Roxb.) Moon is a traditional medicinal plant well known for its pharmacological activities and several bioactive compounds. However, its allelopathy and related substances have not been reported. Hence, the present study was conducted to explore the allelopathic potential and substances from M. tenacissima leaves. Aqueous methanol extracts of M. tenacissima showed significant inhibitory activities against the growth of cress (Lepidium sativum L.) and Italian ryegrass (Lolium multiflorum Lam.). The extracts were purified through various chromatography steps, and two allelopathic substances were isolated and determined by spectral data to be steroidal glycoside 1 (5,6-dihydrogen-11 alpha-O-acetyl-12 beta-O-tigloyl-17 beta-marsdenin), a novel compound, and steroidal glycoside 2 (5,6-dihydrogen-11 alpha,12 beta-di-O-tigloyl-17 beta-marsdenin). Both compounds significantly inhibited the growth of cress seedlings. Steroidal glycoside 1 showed 1.6- and 4-times greater growth inhibitory potential against the cress shoots and roots than steroidal glycoside 2. The concentrations needed for 50% growth inhibition of the cress seedling shoots and roots were 0.46 and 0.03 mM for steroidal glycoside 1, respectively, and 0.74 and 0.12 mM for steroidal glycoside 2, respectively. Therefore, these results suggest that steroidal glycosides 1 and 2 may be responsible for the allelopathy of the M. tenacissima leaves.

DOI： 10.3390/agronomy12071536

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A 68 mu g amount of an acyclic polyketide, named beru'amide, was isolated from a marine cyanobacterium Okeania sp. Beru'amide contains six unique moieties in its relatively small skeleton. By applying several cutting-edge techniques, including DFT-based chemical shift calculations, we achieved the structure determination and the total synthesis of this highly functionalized scarce natural product. Furthermore, beru'amide was shown to have strong antitrypanosomal activity.

DOI： 10.1021/acs.orglett.2c02013

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Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) is a membrane protein on the endoplasmic reticulum (ER) that transports Ca2+ from the cytosol into the ER. As its function is associated with various biological phenomena, SERCA has been recognized as a promising druggable target. Here, we report the second-strongest SERCA-inhibitory compound known to date, which we isolated from the marine cyanobacterium Leptochromothrix valpauliae and named iezoside (1). The structure of iezoside (1) is fundamentally different from that of any other SERCA inhibitor, and its potency is the strongest among marine natural products (K-i 7.1 nM). In this article, we report our comprehensive analysis of iezoside (1), which covers its isolation, structural characterization supported by density functional theory (DFT) calculations and statistical analysis, total synthesis, and clarification of the mode of action of its potent antiproliferative activity (IC50 6.7 +/- 0.4 nM against HeLa cells).

DOI： 10.1021/jacs.2c04459

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Caldorazole (1) was isolated from the marine cyanobacterium Caldora sp. collected on Ishigaki Island, Okinawa, Japan. Its structure was determined to be a new polyketide that contained two thiazole rings and an O-methylenolpyruvamide moiety. Caldorazole (1) showed strong cytotoxicity toward tumor cells that had been seeded at a high density. Cell death induced by 1 in HeLa and A431 cells was also observed only in the presence of the glycolysis blocker 2-deoxy-D-glucose (2DG). Co-treatment with 1 and 2DG remarkably decreased ATP levels in these cells. Furthermore, 1 selectively inhibited complex I in the mitochondrial respiratory chain. Thus, 1 was demonstrated to exert cytotoxicity toward human tumor cells by blocking mitochondrial respiration.

DOI： 10.1021/acs.orglett.2c01566

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Amantamide B (1) is a new linear nonapeptide analogue of the cyanobacterial natural product amantamide A (2), and both have methyl ester and butanamide termini. These compounds were discovered in this study from the organic extract of a tropical marine filamentous cyanobacterium, Oscillatoria sp., collected around the Paracel Islands in the South China Sea. The use of LC-MS/MS molecular networking for sample prioritization and as an analytical dereplication tool facilitated the targeted isolation of 1 and 2. These molecules were characterized by spectroscopy and spectrometry, and configurational assignments were determined using chemical degradation and chiral-phase HPLC analysis. Compounds 1 and 2 modulated spontaneous calcium oscillations without notable cytotoxicity at 10 mu M in short duration in vitro testing on primary cultured neocortical neurons, a model system that evaluates neuronal excitability and/or the potential activity on Ca2+ signaling. Both molecules were also found to be moderately cytotoxic in longer duration bioassays, with in vitro IC50 values of 1-10 mu M against CCRF-CEM human T lymphoblastoid cells and U937 human histiocytic lymphoma cells. These formerly undiscovered bioactivities of known compound 2 expand upon its previously reported function as a selective CXCR7 agonist among 168 GPCR targets.

DOI： 10.1021/acs.jnatprod.1c00983

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Allelopathic plants and their related phytotoxic chemicals have been explored as alternatives for environmentally friendly weed management. Dregea volubilis (L.f.) Benth. ex Hook.f., a woody vine, is well-known for its uses in various therapeutic treatments, and several bioactive compounds have been isolated from this species. However, to date, no phytotoxic substances from D. volubilis have been reported. Hence, in this research, we aimed to investigate the allelopathic effect of D. volubilis and characterize its phytotoxic substances. Extracts of D. volubilis exhibited significant inhibitory activity against the seedling growth of Italian ryegrass (Lolium multiflorum Lam.) and cress (Lepidium sativum L.). The extracts were purified through several chromatography steps, yielding two phytotoxic substances, and using spectroscopy, their structures were determined as dehydrovomifoliol and loliolide. The compounds inhibited the Italian ryegrass and cress seedlings with the I-50 (concentrations needed for 50% inhibition) values ranging from 0.022 to 0.102 mM, for loliolide and 3.24-4.60 mM, for dehydrovomifoliol. These results suggest that both phytotoxic compounds might be responsible for the allelopathy of D. volubilis, and they may be released into the soil through the decomposition of the D. volubilis leaf and probably act as allelopathic active substances. Therefore, the extracts of D. volubilis and its related phytotoxic compounds may be applied as biological agents for controlling weeds.

DOI： 10.3390/agronomy12020303

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Senna garrettiana (Craib) Irwin & Barneby (Fabaceae) is a medicinal plant known to be rich in biologically active compounds that could be exploited to produce bioherbicides. The present study was conducted to explore the allelopathic potential and phytotoxic substances of S. garrettiana. Extracts of S. garrettiana leaves were found to significantly inhibit the growth of Lepidium sativum L. and Echinochloa crus-galli (L.) P. Beauv. (p <= 0.05). The phytotoxic substances were isolated and identified as vanillic acid and ferulic acid by bioassay-directed fractionation and spectral data analysis. The two compounds were shown to significantly inhibit the seed germination, seedling growth, and dry biomass of L. sativum. Based on the concentration required for 50% growth inhibition (defined as IC50), the roots of L. sativum were the most sensitive to the compounds, and the inhibitory effect of ferulic acid (IC50 = 0.62 mM) was >1.3 times more potent than that of vanillic acid (IC50 = 0.82 mM). In addition, a mixture of the two compounds (0.3 mM) resulted in synergistic inhibitory activity against the L. sativum roots compared with the individual compounds. These results suggest that the extracts of S. garrettiana leaves and their phytotoxic compounds have potential as candidate natural herbicides.

DOI： 10.3390/agronomy12010139

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Odookeanynes A (1) and B (2), two acetylene-containing lipopeptides, were isolated from an Okeania sp. marine cyanobacterium collected in Okinawa, Japan. Their structures were elucidated by spectroscopic analysis and Marfey's analysis of acid hydrolysates. Odookeanynes A (1) and B (2) dose-dependently promoted the differentiation of mouse 3T3-L1 preadipocytes in the presence of insulin.

DOI： 10.1021/acs.jnatprod.1c00915

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Metasequoia glyptostroboides Hu et W.C. Cheng is one of the oldest living conifer species, and it has remained unchanged for millions of years compared to its fossils from the Cretaceous period. The species are cultivated in the parks, gardens, and roadsides in many countries. We investigated the allelopathy and allelopathic substances in fallen leaves of M. glyptostroboides. An aqueous methanol extract of the fallen leaves inhibited the growth of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), Lolium multiflorum Lam., Phleum pretense L., and Vulpia myuros (L.) C.C.Gmel. The extract was then purified by several chromatographic steps, and two allelopathic substances were isolated and determined by spectral data to be (+)-rhododendrol and 9-epi-blumenol C. The compound inhibited the growth of cress and L. multiflorum. M. glyptostroboides is a deciduous perennial tree, and accumulation of its fallen leaves occur on the soil under the trees. Therefore, those allelopathic substances in the fallen leaves may be liberated into the rhizosphere soil during the decomposition process of fallen leaves and provide a competitive advantage for M. glyptostrob through the growth inhibition of competing plant species nearby. Therefore, M. glyptostroboides is allelopathic, and (+)-rhododendrol and 9-epi-blumenol C may be contribute to the allelopathy.

DOI： 10.3390/agronomy12010083

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNITED ARAB EMIRATES UNIV  

Clerodendrum indicum (L.) Kuntze (Lamiaceae), an annual shrub, is renowned for being used in folk medicine in South Asian countries. Several pharmacological properties and many bioactive secondary metabolites from C. indicum have been well documented. However, the phytotoxic activities and the related phytotoxic substances with the allelopathic activity of C. indicum have not yet been reported. Thus, we explored the phytotoxic activity of C. indicum and identified its phytotoxic substance. In the experiment, the dry C. indicum leaves were extracted with aqueous methanol, and then the filtrate of the extracts was concentrated using a rotary evaporator to obtain crude extracts. The C. indicum crude extracts significantly inhibited the shoots and roots of six target species: alfalfa, cress, lettuce, barnyard grass, Italian ryegrass, and timothy. The inhibition increased when the extract concentration was increased. The crude extracts of C. indicum were separated in several chromatography steps, and a phytotoxic substance was isolated and characterized using spectroscopy as p-coumaric acid. p-Coumaric acid significantly suppressed the growth of lettuce and timothy seedlings at concentrations greater than 0.3 and 1 mM, respectively. The concentrations of p-coumaric acid required for 50% inhibition (I-50) of the shoots and roots of lettuce and timothy were 0.65 and 0.17 mM, and 0.81 and 0.67 mM, respectively. This study is the first report on isolating p-coumaric acid in C. indicum. The results, therefore, suggest that p-coumaric acid may partly contribute to the phytotoxic properties of C. indicum.

DOI： 10.9755/ejfa.2021.v33.i10.2779

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Iheyamide A (1) is an antitrypanosomal linear peptide isolated from a Dapis sp. marine cyanobacterium by our group in 2020, and based on structure-activity relationships of its natural analogues, the C-terminal pyrrolinone moiety has been identified as the phamacophore for its antiparasitic activity. Further, we isolated this pyrrolinone moiety by itself as a new natural product from the marine cyanobacterium and named it iheyanone (2). As expected, iheyanone (2) showed antitrypanosomal activity, but its potency was weaker than iheyamide A (1). To clarify more detailed structure-activity relationships, we completed a total synthesis of iheyamide A (1) along with iheyanone (2) and evaluated the antitrypanosomal activities of several synthetic intermediates. As a result, we found that the longer the peptide chain, the stronger the antitrypanosomal activity. As iheyamide A (1) showed selective toxicity against Trypanosoma brucei rhodesiense, these findings can provide design guidelines for antitrypanosomal drugs.

DOI： 10.1021/acs.jnatprod.1c00792

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Kinenzoline (1), a new linear depsipeptide, was isolated from a marine Salileptolyngbya sp. cyanobacterium. Its structure was elucidated by spectroscopic analyses and degradation reactions. In addition, we achieved a total synthesis of 1 and confirmed its structure. Kinenzoline (1) showed highly selective antiproliferative activity against the causative organism of sleeping sickness, Trypanosoma brucei rhodesiense (IC50 4.5 μM), compared to normal human cells (WI-38, IC50 > 100 μM). Kinenzoline (1) is a promising lead compound for the development of new antitrypanosomal drugs.

DOI： 10.1021/acs.joc.1c00817

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Bromoiesol sulfates A (1) and B (2), new polyhalogenated aryl sulfates, were isolated from a Salileptolyngbya sp. marine cyanobacterium along with their hydrolyzed compounds, bromoiesols A (3) and B (4). To pick up the candidates of their structures, we used Small Molecule Accurate Recognition Technology (SMART), an artificial intelligence-based structure-prediction tool, and their structures were elucidated on the basis of single-crystal X-ray diffraction analysis of bromoiesols (3 and 4). In addition, to verify the structures, the total synthesis of bromoiesol A sulfate (1) and bromoiesol A (3) was achieved. The bromoiesol family, especially bromoiesols (3 and 4), selectively inhibited the growth of the bloodstream form of Trypanosoma brucei rhodesiense, the causative agent of human African sleeping sickness.

DOI： 10.1021/acs.joc.1c01214

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To protect our environment from the toxic effect of herbicides, it is necessary to reduce the application of synthetic herbicides for controlling weeds in crop fields as well as to increase the use of natural herbicides produced from plant sources. Phytotoxic compounds obtained from plant species have gained attention as an alternate biological method for managing weeds. Albizia richardiana was previously reported to contain a number of phytotoxic substances. Therefore, we carried out this study to investigate more allelopathic substances in Albizia richardiana leaves. Aqueous methanol extracts of Albizia richardiana leaves were significantly inhabited the seedling growth of the two test species (alfalfa and timothy) in a concentration-dependent manner. The two most active substances were separated through different chromatographic steps and characterized as a novel compound 3-hydroxy-4-oxo-β-dehydroionol [(E)-6-hydroxy-3-(3-hydroxybut-1-en-1-yl)-2,4,4-trimethylcyclohexa-2,5-dien-1-one], and compound 3-oxo-α-ionone [3,5,5-trimethyl-4-(3-oxo-1-butenyl)-2-cyclohexen-1-one]. The novel compound 3-hydroxy-4-oxo-β-dehydroionol showed relatively stronger growth inhibitory potential compare to the compound 3-oxo-α-ionone and significantly restricted the seedling growth of crees and timothy. The required concentration for 50% reduction in the growth (I50 values) of the cress and timothy seedlings varied from 63.78 to 141.61 μM for 3-hydroxy-4-oxo-β-dehydroionol and 1059.60 to 1616.10 μM for 3-oxo-α-ionone. The results indicate that these two allelopathic compounds may be responsible for the phytotoxicity of Albizia richardiana leaves.

DOI： 10.1016/j.eti.2021.101779

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Metabolomics can be used to study complex mixtures of natural products, or secondary metabolites, for many different purposes. One productive application of metabolomics that has emerged in recent years is the guiding direction for isolating molecules with structural novelty through analysis of untargeted LC-MS/MS data. The metabolomics-driven investigation and bioassay-guided fractionation of a biomass assemblage from the South China Sea dominated by a marine filamentous cyanobacteria, cf. Neolyngbya sp., has led to the discovery of a natural product in this study, wenchangamide A (1). Wenchangamide A was found to concentration-dependently cause fast-onset apoptosis in HCT116 human colon cancer cells in vitro (24 h IC50 = 38 μM). Untargeted metabolomics, by way of MS/MS molecular networking, was used further to generate a structural proposal for a new natural product analogue of 1, here coined wenchangamide B, which was present in the organic extract and bioactive sub-fractions of the biomass examined. The wenchangamides are of interest for anticancer drug discovery, and the characterization of these molecules will facilitate the future discovery of related natural products and development of synthetic analogues.

DOI： 10.3390/md19070397

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Lingaoamide (1), a new cyclic heptapeptide natural product, was isolated from a freshwater Oscillatoria cyanobacterium. The producing organism was collected in Chinese water spinach paddy farm fields in Lingao County, Hainan, China. The structure of 1 was determined by conventional mass spectrometry, NMR spectroscopy, and chemical degradation studies. Lingaoamide concentration-dependently up-regulates the biogenesis of pro-pathogenic melanin pigments (melanogenesis) in the rice blast fungus, Magnaporthe grisea, when tested in vitro. This molecule also exhibits weak in vitro inhibition (MIC 32 mu g/mL) of Gram-negative Pseudomonas aeruginosa and Gram-positive Bacillus pumilus, and does not appear to impact plant growth or immune response in vivo using the model organism, Arabidopsis thaliana. (C) 2021 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2021.153214

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Motobamide (1), a new cyclic peptide containing a C-prenylated cyclotryptophan residue, was isolated from a marine Leptolyngbya sp. cyanobacterium. Its planar structure was established by spectroscopic and MS/MS analyses. The absolute configuration was elucidated based on a combination of chemical degradations, chiral-phase HPLC analyses, spectroscopic analyses, and computational chemistry. Motobamide (1) moderately inhibited the growth of bloodstream forms of Trypanosoma brucei rhodesiense (IC50 2.3 μM). However, it exhibited a weaker cytotoxicity against normal human cells (IC50 55 μM).

DOI： 10.1021/acs.jnatprod.1c00234

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DOI： 10.1021/acs.jnatprod.1c00282

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The linear lipopeptides komesuamide (1) and odopenicillatamide (2) were isolated from Caldora penicillata a marine cyanobacterium collected in Okinawa. The structures of these compounds were established by spectroscopic analyses, and the absolute configurations were determined by HPLC analyses of the acid hydrolysates. Both compounds showed glucose uptake activity at 40 mM in cultured L6 myotubes. (C) 2021 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2021.131969

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

We conducted an investigation to search for the possibility of phytotoxic compounds and then identify them in C. aciculatus. The aqueous methanol extracts of C. aciculatus imposed a strong suppressive effect on the shoots and roots growth of Medicago sativa and Echinochloa crus-galli. The C. aciculatus extracts were subsequently purified through chromatography and three growth-inhibitory compounds were identified by spectral data as methyl cis-p-coumarate, methyl trans-p-coumarate, and trans-ferulaldehyde. The seedlings growth of Lepidium sativum was suppressed by methyl cis-p-coumarate, methyl trans-p-coumarate, and trans-ferulaldehyde. The I50 values (concentration required for 50% growth inhibition) for the seedling growth of L. sativum ranged from 1.25 to 1.73 mM for methyl cis-p-coumarate, 0.74 to 1.23 mM for methyl trans-p-coumarate, and 1.05 to 1.84 mM for trans-ferulaldehyde. Our finding indicates that methyl cis-p-coumarate, methyl trans-p-coumarate, and trans-ferulaldehyde may contribute to the phytotoxic effects of C. aciculatus.

DOI： 10.1007/s11738-021-03221-5

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The allelopathic potential of plant species and their related compounds has been increasingly reported to be biological tools for weed control. The allelopathic potential of Garcinia xanthochymus was assessed against several test plant species: lettuce, rapeseed, Italian ryegrass, and timothy. The extracts of G. xanthochymus leaves significantly inhibited all the test plants in a concentration- and species-specific manner. Therefore, to identify the specific compounds involved in the allelopathic activity of the G. xanthochymus extracts, assay-guided purification was carried out and two allelopathic compounds were isolated and identified as methyl phloretate {3-(4-hydroxyphenyl) propionic acid methyl ester} and vanillic acid (4-hydroxy-3-methoxybenzoic acid). Both of the substances significantly arrested the cress and timothy seedlings growth. I-50 values (concentrations required for 50% inhibition) for shoots and roots growth of the cress and timothy were 113.6-104.6 and 53.3-40.5 mu M, respectively, for methyl phloretate, and 331.6-314.7 and 118.8-107.4 mu M, respectively, for vanillic acid, which implied that methyl phloretate was close to 3- and 2-fold more effective than vanillic acid against cress and timothy, respectively. This report is the first on the presence of methyl phloretate in a plant and its phytotoxic property. These observations suggest that methyl phloretate and vanillic acid might participate in the phytotoxicity of G. xanthochymus extract.

DOI： 10.3390/app11052264

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Authorship：Lead author   Language：Japanese   Publisher：SOC SYNTHETIC ORGANIC CHEM JPN  

Natural products, well known for unique chemical diversity and bioactivity, are the compounds that organisms have acquired in evolutionary history. They have attracted attentions from not only organic chemists but also scientists in related fields and have provided breakthroughs for science. Against this background, we have investigated the secondary metabolites of marine organisms, especially cyanobacteria, and have discovered various novel bioactive compounds. In this account, our recent research activities regarding the isolation, structure determination, total syntheses and biological activities of our novel natural products are described.

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Albizia richardiana, a fast-growing, large deciduous tree belonging to the Fabaceae family, grows well in hot and humid areas but mainly grows in the tropics of the Old World. The medicinal and other uses of Albizia richardiana are well documented, but the phytotoxic effects of this tree have not yet been investigated. We conducted this study to investigate the phytotoxic activity of Albizia richardiana leaves and to identify growth inhibitory substances for controlling weeds in a sustainable way. Aqueous methanol extracts of Albizia richardiana leaves greatly suppressed the growth of cress and barnyard grass seedlings in a concentration- and species-dependent manner. Two phytotoxic substances were separated using several purification steps and characterized through spectral analysis as dehydrovomifoliol and loliolide. Dehydrovomifoliol and loliolide significantly arrested the seedling growth of cress in the concentrations of 0.1 and 0.01 mM, respectively. The extract concentrations needed for 50% growth inhibition (I-50 values) of cress seedlings were 3.16-3.01 mM for dehydrovomifoliol and 0.03-0.02 mM for loliolide. The results suggest that these two allelopathic substances might play a vital role in the phytotoxicity of Albizia richardiana leaves.

DOI： 10.3390/app11041455

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Hoshinoamide C (1), an antiparasitic lipopeptide, was isolated from the marine cyanobacterium Caldora penicillata. Its planar structure was elucidated by spectral analyses, mainly 2D NMR, and the absolute configurations of the α-amino acid moieties were determined by degradation reactions followed by chiral-phase HPLC analyses. To clarify the absolute configuration of an unusual amino acid moiety, we synthesized two possible diastereomers of hoshinoamide C and determined its absolute configuration based on a comparison of their spectroscopic data with those of the natural compound. Hoshinoamide C (1) did not exhibit any cytotoxicity against HeLa or HL60 cells at 10 μM, but inhibited the growth of the parasites responsible for malaria (IC50 0.96 μM) and African sleeping sickness (IC50 2.9 μM).

DOI： 10.1021/acs.jnatprod.0c01209

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Wedelia chinensis (Asteraceae) is a wetland herb native to India, China, and Japan. It is a valuable medicinal plant recorded to have pharmaceutical properties. However, the phytotoxic potential of Wedelia chinensis has not yet been examined. Thus, we carried out this study to establish the allelopathic effects of Wedelia chinensis and to identify its phytotoxic substances. Extracts of Wedelia chinensis exhibited high inhibitory activity against the root and shoot growth of cress, alfalfa, rapeseed, lettuce, foxtail fescue, Italian ryegrass, timothy, and barnyard grass. The inhibition was varied with species and was dependent on concentrations. The extracts were separated through several purification steps, and the two effective substances were isolated and characterized as vanillic acid and gallic acid using spectral analysis. Vanillic acid and gallic acid significantly arrested the growth of cress and Italian ryegrass seedlings. The concentrations of vanillic acid and gallic acid needed for 50% inhibition (I50 values) of the seedling growth of the cress and Italian ryegrass were 0.04-15.4 and 0.45-6.6 mM, respectively. The findings suggest that vanillic acid and gallic acid may be required for the growth inhibitory activities of Wedelia chinensis.

DOI： 10.3390/foods9111591

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Chemical investigation on a marine sponge, Dactylospongia elegans, yielded five new γ-oxygenated butenolide sesterterpene derivatives, dactylospenes A-E (1-5), as well as two known biosynthetically related compounds, luffariellolide (6) and furospinosulin B (7). The structures of these compounds were elucidated on the basis of their spectroscopic data, experimental and calculated electronic circular dichroism (ECD) analysis, as well as comparison of the NMR data with those of known analogs. These metabolites are the first γ-oxygenated butenolide sesterterpenes to be reported from this genus. These compounds were evaluated in antimicrobial, anti-inflammatory, and cytotoxic assays. Only compounds 1, 3, and 6 exhibited moderate cytotoxicity against DU145, SW1990, Huh7, and PANC-1 cancer cell lines with IC50 values in the range of 2.11-13.35 μM. Furthermore, compound 2, without cytotoxicity, exhibited significant inhibitory effects (inhibitory rate 77.5%) on nitric oxide production induced by lipopolysaccharide at 10 μM.

DOI： 10.3390/md18100491

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

The phytotoxic potential of the leaves and twigs of Schumannianthus dichotomus, discarded in the mat-making industry against four test plants (lettuce (Lactuca sativa L.), rapeseed (Brassica napus L.), foxtail fescue (Vulpia myuros (L.) C.C. Gmel.) and timothy (Phleum pratense L.)) was investigated and found strong phytotoxic activity. An assay-guided fractionation of S. dichotomus extarcts against cress (Lepidium sativum L.) through a series of column chromatography steps yielded two compounds, 8-(5-oxo-2,5-dihydrofuran-2-yl) octanoic acid (ODFO) and (E)-6-hydroxy-2,6-dimethylocta-2,7-dienoic acid (8-carboxylinalool). ODFO and 8-carboxylinalool showed strong phytotoxic activity against cress and timothy. The concentrations required for 50% growth inhibition (I50 value) of the seedlings of cress and timothy were 111.94-128.01 and 36.30-91.75 µM, respectively, for ODFO, but the values were much higher at 315.98-379.13 and 107.92-148.41 µM, respectively, for 8-carboxylinalool, indicating the stronger phytotoxic activity of ODFO. This study is the first to isolate ODFO and 8-carboxylinalool from S. dichotomus and their phytotoxic potential while ODFO is firstly encountered from any natural source. The growth inhibitory activity of the identified compounds may explain their role in the phytotoxic activity of S. dichotomus, which suggests the possible use of its leaves and twigs or its active constituents as natural bioherbicides.

DOI： 10.1080/03601234.2020.1822716

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNITED ARAB EMIRATES UNIV  

In forestry systems, many types of forest trees possess allelopathic properties and release a wide variety of allelochemicals that influence the growth and development of surrounding species. Dalbergia cochinchinensis, a forest tree distributed in Southeast Asia, is reputed to possess several biological properties and contain several secondary compounds. However, there have been no studies on the allelopathy of D. cochinchinensis. Therefore, D. cochinchinensis leaf extracts were examined for allelopathic potential. The present study showed that D. cochinchinensis extracts significantly inhibited the seedling growth of six test plant species: timothy, Italian ryegrass, barnyard grass, cress, alfalfa, and lettuce. Concentrations of the D. cochinchinensis extracts negatively correlated with the shoot length (r =-0.50 to -0.89) and root length (r =-0.65 to -0.89) of all the test plant species. The extracts were then purified using several chromatographic steps and the growth inhibitory substance was isolated. The chemical structure of the substance was identified through spectroscopic analysis as 3,4-dihydroxybenzoic acid (protocatechuic acid). Protocatechuic acid at a concentration higher than 3 mM significantly inhibited the growth of cress seedlings, whereas barnyard grass seedlings were inhibited at concentrations higher than 0.3 mM. As the protocatechuic acid concentration increased, the seedling growth of cress and barnyard grass was significantly reduced. I-50 values showed the effectiveness of protocatechuic acid against both test plant species was apparently greater on root growth than shoot growth. Results of this study suggest that protocatechuic acid isolated from D. cochinchinensis might be responsible for its inhibitory effects.

DOI： 10.9755/ejfa.2020.v32.i7.2130

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Irijimasides A-E (1-5), a series of new 14-membered macrolide glycosides, were isolated from a marine cyanobacterium collected in Okinawa. The gross structures of 1-5 were established by spectroscopic analysis, including 2D NMR, while absolute stereostructures were determined based on NOESY spectra, chemical derivatization, and ECD data. All five macrolides suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced tartrate-resistant acid phosphatase (TRAP) activity in mouse RAW264 macrophage cells, indicating that these compounds inhibit osteoclast formation.

DOI： 10.1021/acs.jnatprod.0c00042

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Iheyamides A (1), B (2), and C (3), new linear peptides, were isolated from a marine Dapis sp. cyanobacterium. Their structures were elucidated by spectroscopic analyses and degradation reactions. Iheyamide A (1) showed moderate antitrypanosomal activities against Trypanosoma brucei rhodesiense and Trypanosoma brucei brucei (IC50 = 1.5 μM), but the other two analogues, iheyamides B (2) and C (3), did not (IC50 > 20 μM, respectively). The structure-activity relationship clarified that an isopropyl-O-Me-pyrrolinone moiety was necessary for the antitrypanosomal activity. Furthermore, the cytotoxicity of 1 against normal human cells, WI-38, was 10 times weaker than its antitrypanosomal activity (IC50 = 18 μM).

DOI： 10.1021/acs.jnatprod.0c00250

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

© 2020 Elsevier Ltd Wedelia chinensis has been widely used as a traditional medicine and several bioactive compounds have been isolated. We investigated phytotoxic property and phytotoxic substances in the species. An aqueous methanol extract of W. chinensis inhibited the growth of roots and shoots of cress. The extracts were then purified by several chromatographic runs with monitoring the inhibitory activity and a phytotoxic substance was isolated. The substance was determined by spectral data to be a novel kaurene-type compound, wedelienone. Wedelienone inhibited the growth of cress and timothy (Phleum pratense L) at concentrations greater than 10–30 μM. These results suggest that wedelienone may contribute to the phytotoxic effects caused by the extracts.

DOI： 10.1016/j.tetlet.2020.151600

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An antimalarial lipopeptide, ikoamide, was isolated from an Okeania sp. marine cyanobacterium. Its gross structure was established by spectroscopic analyses, and the absolute configuration was clarified based on a combination of chiral-phase HPLC analyses, spectroscopic analyses, and derivatization reactions. Ikoamide showed strong antimalarial activity with an IC50 value of 0.14 μM without cytotoxicity against human cancer cell lines at 10 μM.

DOI： 10.1021/acs.jnatprod.9b01147

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The phytotoxic potential of plants and their constituents against other plants is being increasingly investigated as a possible alternative to synthetic herbicides to control weeds in crop fields. In this study, we explored the phytotoxicity and phytotoxic substances of Schumannianthus dichotomus, a perennial wetland shrub native to Bangladesh, India, and Myanmar. Leaf extracts of S. dichotomus exerted strong phytotoxicity against two dicot species, alfalfa and cress, and two monocot species, barnyard grass and Italian ryegrass. A bioassay-driven purification process yielded two phenolic derivatives, syringic acid and methyl syringate. Both constituents significantly inhibited the growth of cress and Italian ryegrass in a concentration-dependent manner. The concentrations required for 50% growth inhibition (I50 value) of the shoot and root growth of cress were 75.8 and 61.3 μM, respectively, for syringic acid, compared with 43.2 and 31.5 μM, respectively, for methyl syringate. Similarly, to suppress the shoot and root growth of Italian rye grass, a greater amount of syringic acid (I50 = 213.7 and 175.9 μM) was needed than methyl syringate (I50 = 140.4 to 130.8 μM). Methyl syringate showed higher phytotoxic potential than syringic acid, and cress showed higher sensitivity to both substances. This study is the first to report on the phytotoxic potential of S. dichotomus and to identify phytotoxic substances from this plant material.

DOI： 10.3390/plants9010102

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Eleocharis atropurpurea is an annual weed and distributed widely in pantropical and subtropical regions. Yet, there have been no studies on the allelopathy of E. atropurpurea. Therefore, we investigated the allelopathic potential of E. atropurpurea to identify allelopathic substances from it. The aqueous methanolic extracts of E. atropurpurea showed an inhibitory effect on the seedling growth of lettuce, rapeseed, barnyard grass and foxtail fescue. Inhibition was species- and concentration-dependent. Two substances, syringaldehyde and acetosyringone, were isolated by using chromatography and using spectroscopy their structures were determined. Syringaldehyde and acetosyringone inhibited the shoot and root growth of cress and barnyard grass at concentrations greater than 3.0 mM except shoot growth of barnyard grass by acetosyringone. Concentration and seedling growth of cress and barnyard grass displayed a negative correlation. The I 50 values of syringaldehyde and acetosyringone for the shoot and root growth of cress were 1.67 and 1.61 mM, and 1.49, and 1.29 mM, respectively, whereas for the shoot and root growth of barnyard grass the values were 4.09 and 2.41 mM, and 4.54 and 1.92 mM, respectively. Therefore, it is suggested that these compounds may contribute to the inhibitory effects of E. atropurpurea.

DOI： 10.1080/11263504.2020.1762779

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Cyatheaceae (tree ferns) appeared during the Jurassic period and some of the species still remain. Those species may have some morphological and/or physiological characteristics for survival. A tree fern was observed to suppress the growth of other ligneous plants in a tropical forest. It was assumed that the fern may release toxic substances into the forest floor, but those toxic substances have not yet been identified. Therefore, we investigated the phytotoxicity and phytotoxic substances of Cyathea lepifera (J. Sm. ex Hook.) Copel. An aqueous methanol extract of C. lepifera fronds inhibited the growth of roots and shoots of dicotyledonous garden cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), and alfalfa (Medicago sativa L.), and monocotyledonous ryegrass (Lolium multiflorum Lam.), timothy (Phleum pratense L.), and barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.). The results suggest that C. lepifera fronds may have phytotoxicity and contain some phytotoxic substances. The extract was purified through several chromatographic steps during which inhibitory activity was monitored, and p-coumaric acid and (-)-3-hydroxy-β-ionone were isolated. Those compounds showed phytotoxic activity and may contribute to the phytotoxic effects caused by the C. lepifera fronds. The fronds fall and accumulate on the forest floor through defoliation, and the compounds may be released into the forest soils through the decomposition process of the fronds. The phytotoxic activities of the compounds may be partly responsible for the fern's survival.

DOI： 10.3390/plants9010046

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The bioassay-guided fractionation of an Okeania sp. marine cyanobacterium collected in Okinawa led to the isolation of the lipopeptide mabuniamide (1). The gross structure of 1 was determined by spectroscopic analyses, and its absolute configuration was determined using Marfey's analysis of the acid hydrolysate of 1. The absolute configuration of 1 was confirmed by total synthesis. Mabuniamide (1) stimulated glucose uptake in cultured rat L6 myotubes. In addition, mabuniamide (1) and its stereoisomer (2) exhibited moderate antimalarial activity.

DOI： 10.1021/acs.jnatprod.9b00749

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Nine new linear lipopeptides, microcolins E-M (1-9), together with four known related compounds, microcolins A-D (10-13), were isolated from the marine cyanobacterium Moorea producens using bioassay-guided and LC-MS/MS molecular networking approaches. Catalytic hydrogenation of microcolins A-D (10-13) yielded two known compounds, 3,4-dihydromicrocolins A and B (14, 15), and two new derivatives, 3,4-dihydromicrocolins C and D (16, 17), respectively. The structures of these new compounds were determined by a combination of spectroscopic and advanced Marfey's analysis. Structurally unusual amino acid units, 4-methyl-2-(methylamino)pent-3-enoic (Mpe) acid and 2-amino-4-methylhexanoic acid (N-Me-homoisoleucine), in compounds 1-3 and 8, respectively, are rare residues in naturally occurring peptides. These metabolites showed significant cytotoxic activity against H-460 human lung cancer cells with IC50 values ranging from 6 nM to 5.0 μM. The variations in structure and attendant biological activities provided fresh insights concerning structure-activity relationships for the microcolin class of lipopeptides.

DOI： 10.1021/acs.jnatprod.9b00549

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Plants are sources of diversified allelopathic substances that can be investigated for use in eco-friendly and efficient herbicides. An aqueous methanol extract from the leaves of Garcinia xanthochymus exhibited strong inhibitory activity against barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), foxtail fescue (Vulpia myuros (L.) C.C.), alfalfa (Medicago sativa L.), and cress (Lepidium sativum L.), and appears to be a promising source of allelopathic substances. Hence, bio-activity guided purification of the extract through a series of column chromatography steps yielded a novel compound assigned as garcienone ((R, E)-5-hydroxy-5-((6S, 9S)-6-methyl-9-(prop-13-en-10-yl) tetrahydrofuran-6-yl) pent-3-en-2-one). Garcienone significantly inhibited the growth of cress at a concentration of 10 μM. The concentrations resulting in 50% growth inhibition (I50) of cress roots and shoots were 120.5 and 156.3 μM, respectively. This report is the first to isolate and identify garcienone and to determine its allelopathic potential.

DOI： 10.3390/plants8090301

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Cancer remains one of the most lethal diseases worldwide. There is an urgent need for new drugs with novel modes of action and thus considerable research has been conducted for new anticancer drugs from natural sources, especially plants, microbes and marine organisms. Marine populations represent reservoirs of novel bioactive metabolites with diverse groups of chemical structures. This review highlights the impact of marine organisms, with particular emphasis on marine plants, algae, bacteria, actinomycetes, fungi, sponges and soft corals. Anti-cancer effects of marine natural products in in vitro and in vivo studies were first introduced; their activity in the prevention of tumor formation and the related compound-induced apoptosis and cytotoxicities were tackled. The possible molecular mechanisms behind the biological effects are also presented. The review highlights the diversity of marine organisms, novel chemical structures, and chemical property space. Finally, therapeutic strategies and the present use of marine-derived components, its future direction and limitations are discussed.

DOI： 10.3390/md17090491

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Iriomoteolide-2a is a marine macrolide metabolite isolated from a cultured broth of the benthic dinoflagellate Amphidinium sp. HYA024 strain. This naturally occurring substance was reported to show remarkable cytotoxic activity against human cancer cell lines HeLa and DG-75 and in vivo antitumor activity against murine leukemia P388 cell line. Herein, the total synthesis, stereochemical revision, and biological assessment of iriomoteolide-2a are reported in detail. Total synthesis of the proposed structure 1 of iriomoteolide-2a featured a late-stage convergent assembly of three components by a Suzuki-Miyaura coupling, an esterification, and a ring-closing metathesis. However, the NMR data of synthetic 1 were not identical to those of the natural product. Careful analysis of the NMR data of the authentic material and synthesis/NMR analysis of appropriately designed model compounds led to consideration of four possible stereoisomers 2-5 as candidates for the correct structure. Accordingly, total syntheses of 2-5 were achieved by taking advantage of the convergent strategy, and comparison of the NMR spectra of synthetic 2-5 with those of the natural product led to the conclusion that 5 shows the correct relative configuration of iriomoteolide-2a. The absolute configuration of this natural product was finally established through chiral HPLC analysis of synthetic 5/ent-5 with the authentic sample. The antiproliferative activity of the synthetic compounds was assessed against HeLa and A549 cells to show that, in contrast to expectation, synthetic 5 and ent-5 were only marginally active in these cell lines. This work clearly underscores the vital role of total synthesis in the establishment of the structure and biological activity of natural products.

DOI： 10.1002/chem.201900813

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© 2019 Weed Science Society of Japan The creeping weed, Chrysopogon aciculatus (Retz.) Trin., is widely known for its use as folk medicine, while its phytotoxic potential has not been examined. Therefore, we carried out an investigation into the phytotoxic potential of C. aciculatus to identify phytotoxic substances. C. aciculatus extracts showed inhibitory effects on shoot and root growth of cress, lettuce, rapeseed, and Italian ryegrass. Inhibition was both species-dependent and concentration-dependent. Two substances, (9S,10E,12Z)-9-hydroxyoctadeca-10,12-dienoic acid (9-HO-ODDEA) and rhizopycnin A, were isolated using chromatographies and characterized by spectral analysis. 9-HO-ODDEA retarded shoot and root growth of cress at concentrations higher than 1.0 and 0.3 mM, respectively, while on cress seedling by rhizopycnin A, the inhibition began from 1.0 mM. The concentrations needed for 50% inhibition of the shoot and root growth of test plants ranged from 1.71–2.31, and 0.71–0.72 mM for 9-HO-ODDEA and rhizopycnin A, respectively. These results indicate that these substances may contribute, to a certain extent, to the phytotoxic activity of C. aciculatus.

DOI： 10.1111/wbm.12175

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Kyanamide (1), a new depsipeptide containing 3-amino-6-hydroxy-2-piperidone moiety, was isolated from the Caldora penicillata marine cyanobacterium collected in Okinawa. Its structure was determined by spectroscopic analysis and Marfey's analysis of acid hydrolysate. Kyanamide exhibited moderate cytotoxicity against HeLa S3 cells. 1 also exhibited potent protease inhibitory activity against elastase and chymotrypsin with IC50 values of 0.13 nM and 1.1 mu M. (C) 2019 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2019.04.046

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Plants  

Anredera cordifolia (Tenore) Steenis is widely planted as an ornamental and medicinal plant in Indonesia. On the other hand, in some other countries this plant is classified as a noxious weed. As a harmful weed, A. cordifolia is reported to have the ability to smother all native vegetation, collapse canopies of tall trees, cultivate as a ground cover and disrupt native seedling development. There is no available information about the involvement of any allelochemicals from A. cordifolia related to these issues. The present study evaluated the allelopathic effect by isolating and identifying the allelopathic substance from A. cordifolia leaf extract. The allelopathic potency of A. cordifolia was determined by a series of bioassays of shoot and root growth on some selected test plants. Separation and purification of the active substances was achieved through several chromatography processes. Finally, the substances with allelopathic activity were identified through high-resolution electrospray ionization mass spectrometry (HRESIMS) analysis and determined by the specific rotation of compound, proton and carbon NMR spectroscopies. The results show that A. cordifolia possesses allelopathic properties which affect other plant species. The isolated compound from the plant material, 3-hydroxy-alpha-ionone, may contribute to the allelopathic effects of A. cordifolia.

DOI： 10.3390/plants8050134

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS INC  

© The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions A plant growth inhibitory substance was isolated from Heliotropium indicum by bioassay-guided purification and characterized to be (+)-isoamericanol A. (+)-Isoamericanol A significantly inhibited seedling growth of cress at a concentration greater than 0.1 mM. The concentrations of (+)-isoamericanol A required for 50% growth inhibition of cress roots and hypocotyls were 0.5 and 0.4 mM, respectively. This inhibition indicates that (+)-isoamericanol A had a growth inhibitory activity and may contribute to the allelopathic effect of H. indicum. This report is the first on the plant growth inhibitory activity of (+)-isoamericanol A as an allelopathic substance.

DOI： 10.1177/1934578X19845788

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© 2019 Weed Science Society of Japan Chinese violet (Asystasia gangetica (L.) T. Anderson) is a perennial invasive weed belonging to Acanthaceae. Leaves of this weed have been suggested to possess phytotoxic activity. However, phytotoxic substances in this weed have not yet been reported. Therefore, the present study investigated phytotoxic activity of Chinese violet extracts and phytotoxic substances. The extracts of Chinese violet leaves inhibited the root and shoot growth of cress, lettuce, alfalfa, barnyard grass, ryegrass, and timothy, where the level of inhibition increased with increasing extract concentrations. Bioassay-guided separations of the extracts led to isolation of two phytotoxic substances, indole-3-carboxaldehyde and (6R,9S)-3-oxo-α-ionol. Indole-3-carboxaldehyde significantly inhibited the root and shoot growth of cress at concentrations ≥100 and 30 μmol L −1 , respectively, and concentrations of the substance required for 50% growth inhibition were 210 and 127 μmol L −1 for cress roots and shoots, respectively. The other substance, (6R,9S)-3-oxo-α-ionol, was reported to have strongly inhibited cress roots and shoots. The present results suggest that Chinese violet contains two phytotoxic substances indole-3-carboxaldehyde and (6R,9S)-3-oxo-α-ionol, and those substances may play an important role in the phytotoxic activity of Chinese violet.

DOI： 10.1111/wbm.12170

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DOI： 10.1016/j.scienta.2019.02.029

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Minnamide A is a lipopeptide with a unique repeating structure consisting of hydroxy and proposed β-branched methyl groups. The absolute configuration of minnamide A was determined by a combination of chemical degradation, chiral HPLC analyses, and synthetic methods. Minnamide A showed growth-inhibitory activity toward HeLa cells with an IC50 value of 0.17 μM and rapidly induced cell death at a concentration of 2 μM. Minnamide A induced the copper-mediated accumulation of reactive oxygen species.

DOI： 10.1021/acs.orglett.9b00135

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNITED ARAB EMIRATES UNIV  

© 2017 United Arab Emirates University. The weedy annual grass Lamium amplexicaule (L.) originated from the Mediterranean region, spreads quickly, and becomes naturalized in areas it invades. It was assumed that volatile phytotoxic substances are one of the invasive characteristics of L. amplexicaule. However, no volatile compound has been found. Therefore, we re-evaluated the allelopathic potential of L. amplexicaule and investigated the phytotoxic substances with allelopathic activity. An extract of L. amplexicaule inhibited the root and shoot growth of Lepidium sativum, Lactuca sativa, Arctium lappa, Lolium multiflorum Lam., Echinochloa crus-galli, and Vulpia myuros, which indicates that the extract has an allelopathic effect. The extract was purified using bioassay-guided chromatographic separations, and a phytotoxic substance with allelopathic activity was isolated and characterized as methyl caffeate. The compound significantly inhibited the root and shoot growth of L. sativum and L. multiflorum. The present results suggest that methyl caffeate may contribute to the allelopathic effect of the L. amplexicaule extracts and consequently, may be partly responsible for the invasive characteristics of the species.

DOI： 10.9755/ejfa.2019.v31.i2.1907

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© 2019, © 2019 Informa UK Limited, trading as Taylor &amp; Francis Group. Cassia alata (Caesalpiniaceae) is a large perennial shrub native to tropical America. It is an important medicinal and ornamental plant and has been reported to possess several pharmacological properties. However, phytotoxic substances from C. alata have not yet been documented in the literature. Therefore, this study seeks to evaluate the phytotoxic potential of C. alata leaves and to identify inhibitory substances for the purpose of eco-friendly weed management. The effect of aqueous methanol extracts of C. alata on the seedling growth of alfalfa, cress, lettuce, rapeseed, barnyard grass, foxtail fescue, Italian ryegrass, and timothy was examined. The level of inhibition of the extracts corresponded to concentration. Several chromatographic steps were performed to separate the extracts, and through spectroscopic analysis, two active substances were isolated and characterised as rutin and syringone. These two active substances significantly inhibited the seedling growth of cress and foxtail fescue. The range of I 50 values (required concentration for 50% growth inhibition) of rutin and syringone for the seedling growth of cress and foxtail fescue were 129.5–417.8 and 160.1–466.5 µM, respectively. These results indicate that the two identified active phytotoxic substances from C. alata may be responsible for its growth inhibitory properties.

DOI： 10.1080/09064710.2019.1603322

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© The Author(s) 2019 Aqueous methanol extracts of Acmella oleracea inhibited the growth of roots and shoots of cress (Lepidum sativum), lettuce (Lactuca sativa), Italian ryegrass (Lolium multiflorum), and barnyard grass (Echinochloa crus-galli) with the extract concentration-dependent manner. The extracts were then purified and 2 growth inhibitory substances were isolated and identified by spectral data as (E,E)-2,4-undecadien-8,10-diynoic acid isobutylamide (compound 1) and nona-(2Z)-en-6,8-diynoic acid 2-phenylethylamide (compound 2). Compound 1 inhibited the growth of cress roots and shoots at concentrations greater than 0.3 mM and that of barnyard grass root at concentrations greater than 0.03 mM. Compound 2 inhibited the growth of cress shoots and barnyard grass roots at concentrations greater than 1 mM. The inhibition on the seedling growth indicates that both compounds had growth inhibitory activity and may contribute to the inhibitory effect of A. oleracea extracts. This is the first report of having growth inhibitory activity of compounds 1 and 2 on plants.

DOI： 10.1177/1934578X19858805

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

Problems related to weed management such as outbreaks of herbicide-resistant weeds have recently increased. An interesting approach to such problems is to use plant materials with phytotoxic activity. Burdock (Arctium lappa L.) is a biennial herb belonging to Asteraceae and is cultivated in several countries. The present study investigated the phytotoxic activity of burdock and its active substances. Extracts of both burdock leaves and roots inhibited the shoot and root growth of cress and barnyard grass, where the level of inhibition increased with increasing extract concentration. The leaf extracts had 2.0-2.5 times higher activity than the root extracts. Bioassay-guided separations of the leaf extracts led to isolation of a phytotoxic substance, onopordopicrin. Onopordopicrin significantly inhibited the shoot and root growth of cress and barnyard grass. The concentrations of the substance required for 50% growth inhibition were 0.27 and 0.26 mM for cress shoots and roots, respectively, and 1.86 and 0.35 mM for barnyard grass shoots and roots, respectively. The present results suggest that burdock leaves have high phytotoxic activity and onopordopicrin may play a major role in the activity. Burdock leaves may be a good resource for weed management.

DOI： 10.1080/03601234.2019.1636600

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRAZILIAN SOC PLANT PHYSIOLOGY  

© 2018, Brazilian Society of Plant Physiology. Plants, which include crops, weeds, and trees, are able to release effective allelochemicals that inhibit the growth and development of other plants. Eleocharis atropurpurea, a small, annual tufted weed, is renowned for being widely found in crop fields, yet there have been no studies on the allelopathy of E. atropurpurea (Cyperaceae). Thus, we explored the allelopathic potential and allelochemicals in E. atropurpurea and found that aqueous methanol extracts of E. atropurpurea inhibited the seedling growth of Lepidium sativum, Medicago sativa, Lolium multiflorum, and Phleum pratense. There was a significant negative correlation between the seedling growth of the test plants and extract concentration. Extracts were purified using several chromatographic steps and one growth inhibitory substance was isolated and identified by spectroscopic analysis as trans-ferulaldehyde. The active substance trans-ferulaldehyde significantly inhibited the shoot and root length of Lepidium sativum at concentrations higher than 1.0 and 3.0 mM, respectively, whereas the seedling length of Echinochloa crus-galli was inhibited by trans-ferulaldehyde at concentrations higher than 3.0 mM. The trans-ferulaldehyde I50 values for the growth of Lepidium sativum and Echinochloa crus-galli were in the range of 0.73–3.68 mM. The growth inhibitory results of this study suggest that trans-ferulaldehyde may be responsible for the inhibitory effects of E. atropurpurea and may contribute to weed allelopathy.

DOI： 10.1007/s40626-018-0130-5

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Natural Products  

Hoshinoamides A (1) and B (2), new acyclic lipopeptides, were isolated from the marine cyanobacterium Caldora penicillata. Their structures were elucidated by spectroscopic analyses and degradation reactions. Hoshinoamides A (1) and B (2) did not exhibit any cytotoxicity against HeLa cells at 10 μM, but inhibited the in vitro growth of the malarial parasite Plasmodium falciparum (IC50 = 0.52 and 1.0 μM, respectively).

DOI： 10.1021/acs.jnatprod.8b00643

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Tetrahedron Letters  

© 2018 Elsevier Ltd Croissamide, a proline-rich cyclic peptide that contains an N-prenylated tryptophan, was isolated from a marine cyanobacterium Symploca sp. Its gross structure was determined by spectroscopic analyses, and the absolute configuration was established based on chiral HPLC analyses of acid hydrolysates.

DOI： 10.1016/j.tetlet.2018.09.016

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Publishing type：Research paper (scientific journal)   Publisher：Acta Horticulturae  

DOI： 10.17660/ActaHortic.2018.1218.28

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Two new jahanyne analogues, jahanene and jahanane, highly N-methylated lipopeptides, were isolated from a marine cyanobacterium Okeania sp., and their structures were determined by NMR and MS. In addition, we achieved total syntheses of the jahanyne family and assessed their activities. The resulting growth-inhibitory activity of jahanyne was nearly one-tenth of the previously reported activity. Furthermore, we found that the degree of unsaturation at the terminus of the fatty acid moiety affected the growth-inhibitory activity against human cancer cells.

DOI： 10.1021/acs.joc.8b00310

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Heliotropium indicum L. belongs to the family Boraginaceae. The plant has been used as a folk medicine because it contains substances of various biological activities. It is also identified as a common weed which grows wildly in crop fields in tropical and subtropical regions of the world. However, there is little information on the allelopathic effect in this plant. Therefore, this study was undertaken to investigate the growth inhibitory effect and to identify the growth inhibitory substances in H. indicum. An aqueous methanol extract of H. indicum inhibited shoot and root growth of barnyard grass, foxtail fescue, timothy, cress, lettuce and rapeseed at concentrations higher than 10 mg dry weight equivalent extract/mL. The concentrations required for 50% growth inhibition (I50) of those test plants ranged from 3-282 mg dry weight equivalent extract/mL. The extract was then separated using a sequence of chromatographic fractionations and a growth inhibitory substance was isolated and identified by spectral analysis as methyl caffeate. Methyl caffeate inhibited the growth of lettuce and foxtail fescue at concentrations higher than 1.0 mM. The results suggest that methyl caffeate may contribute to the growth inhibitory effect of H. indicum and may play an important role in the allelopathic effect of H. indicum.

DOI： 10.1556/018.68.2018.3.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Natural Products  

Izenamides A, B, and C (1-3), new linear depsipeptides, were isolated from a taxonomically distinct marine cyanobacterium. Izenamides A and B contain a statine moiety [(3 S,4 S)-4-amino-3-hydroxy-6-methylheptanoic acid] and inhibited the activity of cathepsin D, an aspartic peptidase. Meanwhile, izenamides did not show growth-inhibitory activity against HeLa, HL60, or MCF-7 cells at up to 10 μM.

DOI： 10.1021/acs.jnatprod.8b00417

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&lt;p&gt;Cogongrass (Imperata cylindrica [L.] Raeusch.) is a perennial rhizomatous grass that belongs to the Poaceae and is widely distributed in tropical, subtropical and temperate regions over the world. The grass is strongly invasive and is suggested to have allelopathic potential. However, limited information is available on allelopathic substances in cogongrass rhizomes. Therefore, the allelopathic potential and substances in cogongrass rhizomes were investigated. The extracts of cogongrass rhizomes inhibited the root and shoot growth of barnyard grass, ryegrass, timothy, cress, lettuce and alfalfa. After bioassay-guided separations of the extracts, four growth inhibitory substances, 5-methoxyflavone, 5,2&#039;-dimethoxyflavone, methyl caffeate and abscisic acid, were isolated. 5-Methoxyflavone, 5,2&#039;-dimethoxyflavone and methyl caffeate significantly inhibited the root and shoot growth of cress at concentrations of ≥0.03-0.3m mol L&lt;sup&gt;-1&lt;/sup&gt; and their concentrations required for 50% growth inhibition were 0.079-0.24, 0.23-1.1 and 0.59-0.88m mol L&lt;sup&gt;-1&lt;/sup&gt;, respectively. The other isolated substance, abscisic acid, has been reported to have strong growth inhibitory activity. Its

DOI： 10.1111/wbm.12144

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRAZILIAN SOC PLANT PHYSIOLOGY  

&lt;p&gt;Caesalpinia mimosoides (Fabaceae) has been used as a folk medicine and reported to have pharmacological properties. However, the phytotoxicity of C. mimosoides has not yet been studied. Therefore, the phytotoxic activity of C. mimosoides leaf and stem extracts was evaluated against the growth of dicotyledonous and monocotyledonous plants. Aqueous methanol extracts of C. mimosoides leaves and stems exhibited inhibitory effects on the growth of all the test plants. The growth of the test plants decreased with the increase of concentrations of the extracts. Comparison of the concentrations required for 50% growth inhibition (I&lt;sub&gt;50&lt;/sub&gt; values) indicates that the leaf extracts had more inhibitory effects than the stem extracts. Thus, the active substances in the leaf extracts were purified using column chromatographic separations and a growth inhibitory substance was isolated and identified as methyl gallate by using spectral analysis. This study reports the first isolation of methyl gallate in C. mimosoides leaves. Methyl gallate at 10 mM completely inhibited the growth of cress shoots and inhibited its roots by 4.7% of control growth. At the same concentration, the shoots and

DOI： 10.1007/s40626-018-0108-3

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Two new pyrrolinone-containing lipopeptides, ypaoamides B (1) and C (2), were isolated from an Okeania sp. marine cyanobacterium collected in Okinawa. Their structures were determined by spectroscopic analysis and Marfey's analysis of acid hydrolysates. Ypaoamides B (1) and C (2) stimulated glucose uptake in cultured rat L6 myotubes. In particular, ypaoamide B (1) showed potent activity and activated AMP-activated protein kinase.

DOI： 10.1021/acs.jnatprod.8b00088

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&lt;p&gt;The first total synthesis of janadolide, a new cyclic polyketide-peptide hybrid possessing a tert-butyl group, is described. The synthesis of an unsaturated hydroxycarboxylic acid was effected via the lithiation of vinyl iodide followed by addition to a Weinreb amide with a tert-butyl group and stereoselective 1,2-reduction. The cyclic structure was constructed by macrolactamization at the amide bond between the proline moiety and fatty acid moiety.&lt;/p&gt;

DOI： 10.1016/j.tetlet.2018.02.034

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&lt;p&gt;A new polyketide with a cis-fused decalin ring scaffold, caldorin, was isolated from the marine cyanobacterium Caldora penicillata. The gross structure and relative configuration were elucidated by spectroscopic analyses. We also clarified that caldorin is a weak SOAT inhibitor and moderate osteoblast differentiation inhibitor. On the other hand, caldorin did not exhibit cytotoxicity against either HeLa or HL60 cells.&lt;/p&gt;

DOI： 10.1016/j.tetlet.2018.02.046

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Biselyngbyaside, an 18-membered macrolide glycoside from marine cyanobacteria, and its derivatives are known to be sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) inhibitors. Recently, a SERCA orthologue of the malaria parasite, PfATP6, has attracted attention as a malarial drug target. To provide a novel drug lead, we designed new synthetic analogs of biselyngbyolide B, the aglycone of biselyngbyaside, based on the co-crystal structure of SERCA with biselyngbyolide B, and synthesized them using the established synthetic route for biselyngbyolide B. Their biological activities against malarial parasites were evaluated.

DOI： 10.1016/j.bmcl.2017.12.050

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS INC  

© 2018 Natural Product Incorporation. Jatropha podagrica Hook. is cultivated as an ornamental plant and is also used in traditional medicine. The species has various pharmacological properties, but it has not yet been investigated for any potential allelopathic activity and allelopathic substances. In this study, an allelopathic active substance was isolated from an aqueous methanol extract of J. podagrica leaves through chromatography and reverse-phase HPLC. The substance was characterized as 6,7- dimethoxychromone by spectral analysis. 6,7-Dimethoxychromone significantly inhibited the shoots and roots of cress at concentrations greater than 0.3 mM. The concentrations required of 6,7-dimethoxychromone for 50% growth inhibition of cress shoots and roots were 0.95 and 0.83 mM, respectively. The inhibitory activity against the seedling growth of cress indicates that 6,7-dimethoxychromone may contribute to the allelopathic effects and may be responsible for the allelopathic activity in J. podagrica. This report is the first on the allelopathic activity of 6,7-dimethoxychromone as an allelopathic substance from J. podagrica.

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DOI： 10.1080/11263504.2017.1338630

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The total synthesis of kanamienamide, an enamide with an enol ether and an 11-membered macrolactone of marine origin, was achieved. The synthesis features the construction of an enamide adjacent to an enol ether by Buchwald amidation and an 11-membered ring by Mitsunobu lactonization. In addition, on the basis of the biological assay of synthetic 1, we clarified that kanamienamide (1) was not an apoptosis-like cell death inducer, as reported in the isolation paper, and revealed its real biological activity as a necrosis-like cell death inducer.

DOI： 10.1021/acs.joc.7b02288

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRAZILIAN SOC PLANT PHYSIOLOGY  

&lt;p&gt;Herbicide use has raised concerns which results in the need to find an alternative approach, using natural methods, of controlling weeds. Phytotoxic substances released from plants have been used to manage weeds biologically. Rumex maritimus, belonging to the Polygonaceae family, is well known to have a wide range of biological properties. However, the phytotoxic properties of R. maritimus is not well documented. Thus, we conducted an investigation into the phytotoxic potential of R. maritimus and attempted to find out its phytotoxic substances. Leaf, stem and root extracts of R. maritimus exhibited a strong inhibitory effects on root and shoot length of Lactuca sativa L., Medicago sativa L., Lolium multiflorum Lam., Phleum pratense L. With increasing extract concentration, inhibition increased. One substance, 2-methoxystypandrone, was purified after a series of chromatography and characterized by spectral data. 2-Methoxystypandrone reduced the seedling length of Lepidium sativum at concentration ≥ 3 μM. The required 50% growth inhibition concentration of Lepidium sativum seedling for 2-methoxystypandrone was ranged 5.8–11.8 μM. Therefore, it is suggested that the phyt

DOI： 10.1007/s40626-017-0095-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Three new compounds of the malyngamide series, 6,8-di-O-acetylmalyngamide 2 (1), 6-O-acetylmalyngamide 2 (2), and N-demethyl-isomalyngamide I (3), were isolated from the marine cyanobacterium Moorea producens. Their structures were determined by spectroscopic analysis and chemical derivatization and degradation. These compounds stimulated glucose uptake in cultured L6 myotubes. In particular, 6,8-di-O-acetylmalyngamide 2 (1) showed potent activity and activated adenosine monophosphate-activated protein kinase (AMPK).

DOI： 10.3390/md15120367

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&lt;p&gt;Paspalum commersonii (Poaceae) is a herbaceous perennial weed distributed in the tropics and subtropics regions and grows mainly in the moist, or even flooded soil. It often appears in the rice field as a competitive weed and difficult to manage. Its strong competitive nature indicates possible allelopathic potential of P. commersonii. However, no studies have been found yet on the allelopathic activity of P. commersonii. Thus, we investigated the allelopathic potential of this weed and determined its allelopathic substances. Aqueous methanol extracts of P. commersonii showed concentration-dependent inhibitory activity on the seedling growth of cress, alfalfa, rapeseed, lettuce, barnyard grass, foxtail fescue, Italian ryegrass, and timothy. Two substances were isolated through bioassay-guided fractionation and their structures were determined through spectral data as dehydrovomifoliol and loliolide. Dehydrovomifoliol and loliolide started inhibiting the shoot and root growth of cress at concentrations greater than 3 and 0.03 mM, respectively. The concentrations required for 50% inhibition (I&lt;sub&gt;50&lt;/sub&gt;) of cress shoot and root growth were 3.34 and &gt;3.50 mM for dehydrovo

DOI： 10.1080/09064710.2017.1401114

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Kohamamides A, B, and C (1-3), new cyclic depsipeptides that belong to the kulolide superfamily, were isolated from an Okeania sp. marine cyanobacterium. Their structures were elucidated by spectroscopic analyses and degradation reactions. Kohamamide B (2) exhibited moderate cytotoxicity against HL60 cells. Although many natural products in the kulolide superfamily have been isolated from cyanobacteria collected in various parts of the world, kohamamides 1-3 are the first members to be isolated from the East Asian marine environment. In addition, unlike other members of this superfamily, kohamamides 1-3 contain a Leu residue adjacent to the Pro residue, rather than another lipophilic amino acid.

DOI： 10.1021/acs.jnatprod.7b00256

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Tithonia diversifolia (Hermsl.) A. Gray is a perennial invasive plant and spreads quickly in the invasive areas. The extracts of T. diversifolia were found to be toxic to several crop plant species such as rice, maize, sorghum, lettuce and cowpea, and several putative allelopathic substances were identified. However, there is limited information available for the effects of T. diversifolia on wild plants including weed plant species. We investigated the allelopathic potential of T. diversifolia extracts on weed plants, and searched for phytotoxic substances with allelopathic activity. An aqueous methanol extract of T. diversifolia leaves inhibited the growth of weed plants, Lolium multiflorum Lam., Phleum pretense L., Echinochloa crus-galli (L.) Beauv. The extract was then purified by several chromatographic runs and a phytotoxic substance with allelopathic activity was isolated and identified by spectral analysis as tagitinin C. The substance inhibited the growth of Lolium multiflorum, Phleum pratense and Echinochloa crus-galli at concentrations greater than 0.1 - 0.3 mM. The present results suggest that T. diversifolia may possess allelopathic potential on weed plants and tagitinin C may be responsible for the allelopathic effects of T. diversifolia. The allelopathic potential of T. diversifolia may contribute to its invasive characteristics.

DOI： 10.1556/018.68.2017.2.6

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Biseokeaniamides A, B, and C (1-3), structurally novel sterol O-acyltransferase (SOAT) inhibitors, were isolated from an Okeania sp. marine cyanobacterium. Their structures were elucidated by spectroscopic analyses and degradation reactions. Biseokeaniamide B (2) exhibited moderate cytotoxicity against human HeLa cancer cells, and compounds 1-3 inhibited both SOAT1 and SOAT2, not only at an enzyme level but also at a cellular level. Biseokeaniamides (1-3) are the first linear lipopeptides that have been shown to exhibit SOAT-inhibitory activity.

DOI： 10.1021/acs.jnatprod.7b00137

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The bioassay-guided fractionation of the Okinawan marine cyanobacterium Okeania sp. led to the isolation of the novel cyclodepsipeptide odobromoamide (1). The gross structure of 1 was determined by spectroscopic analyses, and its absolute stereochemistry was determined using a variety of different methods, including chemical derivatization and degradation followed by HPLC analysis. In addition, odobromoamide (1) exhibited broad-spectrum cytotoxicity against a human cancer cell line panel.

DOI： 10.1246/bcsj.20160417

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In the search for new antiprotozoal substances, hoshinolactam, an antitrypanosomal lactam, was isolated from a marine cyanobacterium. The gross structure was elucidated by spectroscopic analyses, and the absolute configuration was determined by the first total synthesis. Hoshinolactam showed potent antitrypanosomal activity with an IC50 value of 3.9 nM without cytotoxicity against human fetal lung fibroblast MRC-5 cells (IC50 > 25 μM).

DOI： 10.1021/acs.orglett.7b00047

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Organic agriculture emphasized using of biologically originated herbicides and phytotoxic substances are being considered as a replacement to chemical herbicides. Marsilea crenata is an aquatic perennial fern distributed in the South-East Asian countries and is well known for various biological properties. However, to date, there has been no report that addresses the phytotoxicity of Marsilea crenata. Therefore, we explored phytotoxic properties and phytotoxic substances from Marsilea crenata. An aqueous methanol extracts of Marsilea crenata showed inhibition on the seedling growth of cress, lettuce, alfalfa, barnyard grass, Italian ryegrass, and foxtail fescue. Inhibition increased with increasing extract concentration. The extract was purified by several chromatographic steps and two phytotoxic substances were isolated and identified by spectroscopic analysis as loliolide and isololiolide. At the concentration of 30 mu M, loliolide and isololiolide inhibited seedling growth of cress and barnyard grass by 41.3 to 51.1%, and 58.15 to 87.5% of control seedlings, respectively. The concentrations required for 50% inhibition of cress and barnyard grass seedlings ranged from 32.1 to 128.5 mu M for loliolide, 37.0 to 176.2 mu M for isololiolide. These results suggest these compounds may be responsible for phytotoxic effects of Marsilea crenata extract and could be an important part of organic agriculture.

DOI： 10.1007/s12374-016-0408-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURAL PRODUCTS INC  

A phytotoxic compound was isolated from the root extracts of Cymbopogon nardus by bioassay-guided purification and characterized to be myrislignan. Myrislignan significantly inhibited seedling growth of cress at a concentration greater than 100 μM (p &lt; 0.05). The concentrations required for 50% growth inhibition of myrislignan on hypocotyl and root growth of cress were 429 μM and 517 μM, respectively. The inhibition on seedling growth indicated that myrislignan had a phytotoxic activity and may contribute to the phytotoxic effect of C. nardus.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS AS  

The present study was aimed to determine the allelopathic potential of mango (Mangifera indica L.) leaves and to identify allelopathic substances in the leaves. The aqueous methanol extracts of mango leaves inhibited seedling growth of garden cress, radish, rapeseed, foxtail fescue and crabgrass, and the inhibitory effects increased with the increasing extract concentration, suggesting that mango leaves may contain allelopathic substances. The extract was then purified by several chromatographic runs through a bioassay-directed fractionation, and an growth inhibitory substance was isolated and identified by spectral data as methyl-3,4,5-trihydroxybenzoate (methyl gallate). Methyl gallate at the concentration of 10 mM inhibited 98.6% and 99.8% of root and shoot growth of garden cress relative to the control, respectively, and 94.4% and 49.3% of those of foxtail fescue, respectively. The concentrations of methyl gallate required for 50% growth inhibition (I-50) on garden cress roots and shoots were 3.9 and 3.3 mM, and those on foxtail fescue roots and shoots were 1.5 and 9.5 mM, respectively. It is the first report of an allelopathic substance in mango leaves and allelopathic activity of methyl gallate. Therefore, the mango leaves may have potential as a soil additive material for the weed management options.

DOI： 10.1080/09064710.2016.1215517

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

In 2014, the γ-pyrone-containing polyketide, yoshinone A, was isolated from the marine cyanobacterium Leptolyngbya sp. and its structure was determined. Yoshinone A inhibited differentiation of 3T3-L1 cells into adipocytes, with an EC50 value of 420 nM without any cytotoxicity, and therefore is expected to be a lead compound for obesity drugs. To establish its absolute configuration, and to provide sufficient amounts for further research, the total synthesis of yoshinone A was achieved through synthesis of its two possible diastereomers.

DOI： 10.1016/j.phytochem.2016.10.005

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Miuraenamides A and D, cyclodepsipeptides with antimicrobial and antitumor activity, were synthesized. The synthesis of an unsaturated hydroxycarboxylic acid moiety, starting from a chiral epoxide, was achieved by Suzuki-Miyaura coupling as a key step. As a result, the overall yield for miuraenamide A over the longest linear sequence is 3.2%, while the yield of the previously reported procedure is 1.9%. In addition, the cell growth-inhibitory activity and anti-Phytophthora activity of the synthesized compounds were evaluated.

DOI： 10.1021/acs.joc.6b02061

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Kanamienamide, an enamide with an enol ether, was isolated from the marine cyanobacterium Moorea bouillonii. The gross structure was established by spectroscopic analyses, and the relative stereochemistry was elucidated on the basis of the analyses of NOESY correlations and 1H-1H coupling constants. The absolute configuration was determined on the basis of the chiral HPLC analysis of the N-Me-Leu derived from kanamienamide. This is the first report of a natural product that possesses an N-Me-enamide adjacent to an enol ether. Kanamienamide showed growth-inhibitory activity toward HeLa cells with an IC50 value of 2.5 μM and induced apoptosis-like cell death.

DOI： 10.1021/acs.orglett.6b02364

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Urumamide, a novel cyclic depsipeptide that contains a beta-amino acid, was isolated from a marine cyanobacterium Okeania sp. Its gross structure was determined by spectroscopic analyses, and the absolute configuration was established based on Marfey's analyses and chiral HPLC analyses of hydrolysis products. Biologically, urumamide inhibited the growth of human cancer cells. In addition, urumamide inhibited chymotrypsin. (C) 2016 Published by Elsevier Ltd.

DOI： 10.1016/j.tetlet.2016.08.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Janadolide, a new cyclic polyketide-peptide hybrid possessing a tert-butyl group, was isolated from an Okeania sp. marine cyanobacterium. The gross structure was elucidated by spectroscopic analyses, and the absolute configurations of the amino acid moieties were determined by acid hydrolysis and chiral-phase HPLC analyses. The absolute configuration of the two stereogenic centers in the polyketide moiety was elucidated based on a combination of degradation reactions and spectroscopic analyses including the phenyl-glycine methyl ester method. Janadolide showed potent antitrypanosomal activity with an IC50 value of 47 nM without cytotoxicity against human cells at 10 μM.

DOI： 10.1021/acs.jnatprod.6b00171

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The first total synthesis of koshikalide, a 14-membered macrolide that contains three olefins, was achieved. The skipped diene in the cyclic system was efficiently constructed by very mild Stille coupling at low temperature. The absolute stereochemistry was established by comparison of the specific optical rotations of natural and synthesized koshikalide. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2016.06.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN ANTIBIOTICS RESEARCH ASSOC  

DOI： 10.1038/ja.2016.19

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Kurahyne B (2), a new analogue of kurahyne (1), was isolated from the marine cyanobacterium Okeania sp. Its gross structure was elucidated based on spectroscopic analyses, and the absolute configuration was established by total synthesis. Kurahyne B (2) inhibited the growth of both HeLa and HL60 cells, with IC50 values of 8.1 and 9.0 μM, respectively. The growth-inhibitory activity of kurahyne B was the same as kurahyne (1). In parallel, the first total synthesis of kurahyne (1) was also achieved.

DOI： 10.1021/acs.jnatprod.5b00662

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

In 2014, we isolated kurahyne, an acetylene-containing lipopeptide, from a marine cyanobacterial assemblage of Lyngbya sp. Kurahyne exhibited growth-inhibitory activity against human cancer cells, and induced apoptosis in HeLa cells. However, its mode of action is not yet clear. To elucidate its mode of action, we carried out several cell-based assays, and identified the intracellular target molecule of kurahyne as sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA). In addition, we found that kurahyne inhibited the differentiation of macrophages into osteoclasts.

DOI： 10.1016/j.bmcl.2015.09.044

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The first total synthesis of maedamide, an acyclic peptide isolated from a marine cyanobacterial assemblage of Lyngbya sp., was achieved. This synthesis led to reassignment of the allo-D-Ile of maedamide to be which was supported by H-1 and C-13 NMR data. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2015.06.090

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Mebamamides A and B, new lipopeptides with four d-amino acid residues and a 3,8-dihydroxy-9-methyldecanoic acid residue, were isolated from the green alga Derbesia marina. Their gross structures were elucidated by spectroscopic and ESI-ITMS analyses. The absolute configurations except for the two leucines were revealed based on chiral-phase HPLC analyses of the acid hydrolysate and a modified Mosher's method. A distinction between D-Leu and L-Leu in the sequence was established by the application of a dansyl-Edman method to the partial acid hydrolysate. Mebamamide A did not exhibit any growth inhibitory activity against HeLa and HL60 cells at 10 μM, and mebamamide B did not exhibit any growth inhibitory activity against those cells at 100 μM. Additionally, it was suggested that mebamamide B induced the differentiation of HL60 cells into macrophage-like cells at 100 μM.

DOI： 10.1021/acs.jnatprod.5b00168

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

An acetylene-containing lipopeptide, jahanyne, was isolated from the marine cyanobacterium Lyngbya sp. Its gross structure was established by spectroscopic analyses, and the absolute configuration was clarified based on a combination of chiral HPLC analyses, spectroscopic analyses, and derivatization reactions. Jahanyne significantly inhibited the growth of human cancer cells and induced apoptosis in HeLa cells.

DOI： 10.1021/ol5036722

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Three novel compounds, yoshinones A, B1, and B2, were isolated from the marine cyanobacterium Leptolyngbya sp., and their structures were elucidated by NMR spectral analysis. Yoshinone A, but not yoshinone B1 or B2, inhibited the differentiation of 3T3-L1 cells into adipocytes. In addition, yoshinone A did not exhibit cytotoxicity, suggesting that yoshinone A may be useful in studies on the treatment of obesity. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2014.10.032

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Maedamide, a novel chymotrypsin-inhibiting depsipeptide, was isolated from a cyanobacterial assemblage that mostly consisted of Lyngbya sp. Its structure was elucidated by spectroscopic analyses and chiral HPLC analyses of hydrolysis products. Maedamide selectively inhibited chymotrypsin but not elastase and trypsin. In addition, Maedamide strongly inhibited the growth of HeLa cells and HL60 cells. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2014.05.099

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Kurahamide, a new dolastatin 13 analog, was isolated from a marine cyanobacterial assemblage, consisting mostly of Lyngbya sp. Its gross structure was elucidated by spectroscopic analysis, and the stereochemistries were assigned based on a chiral HPLC analysis of hydrolysis products. Kurahamide strongly inhibited elastase and chymotypsin in vitro. In addition, kurahamide moderately inhibited the growth of human cancer cells, including HeLa and HL60 cells.

DOI： 10.1246/bcsj.20140008

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Kurahyne, a new acetylene-containing lipopeptide, was isolated from a cyanobacterial assemblage that mostly consisted of Lyngbya sp. Its structure was elucidated by spectroscopic analyses and chiral HPLC analyses of hydrolysis products. Kurahyne inhibited the growth of human cancer cells and induced apoptosis in HeLa cells, and it seemed to localize in mitochondria.

DOI： 10.1039/c4ra00132j

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A 14-membered macrolide, koshikalide (1), was isolated from the marine cyanobacterium Lyngbya sp., and its planar structure was elucidated by spectroscopic analysis. The relative stereochemistry of C-I I and C-13 was elucidated by NOESY experiments and by an analysis of (1)H-(1)H coupling constants. Koshikalide (1) exhibited weak cytotoxicity against HeLa S(3) cells. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2009.12.041

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A new bromotyrosine-derived metabolite. 20-N-methylpurpuramine E (1), was isolated from the marine sponge Pseudoceratina purpurea. The structure was elucidated by spectroscopic analysis. 20-N-Methylpurpuramine E (1) showed weak cytotoxicity against HeLa S-3 Cells.

DOI： 10.1246/bcsj.81.1026

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