Details of a Researcher - Suenaga, Kiyotake

Papers - Suenaga, Kiyotake

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Ikoamide, an Antimalarial Lipopeptide from an Okeania sp. Marine Cyanobacterium

Iwasaki K., Iwasaki A., Sumimoto S., Matsubara T., Sato T., Nozaki T., Saito-Nakano Y., Suenaga K.

Journal of Natural Products (Journal of Natural Products) 83 ( 2 ) 481 - 488 2020.02

ISSN 01633864

Copyright © 2020 American Chemical Society and American Society of Pharmacognosy. 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.

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Tree fern cyathea lepifera may survive by its phytotoxic property

Ida N., Iwasaki A., Teruya T., Suenaga K., Kato-Noguchi H.

Plants (Plants) 9 ( 1 ) 2020.01

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. 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.

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Phytotoxic activity and identification of phytotoxic substances from Schumannianthus dichotomus

Rob M.M., Hossen K., Iwasaki A., Suenaga K., Kato-Noguchi H.

Plants (Plants) 9 ( 1 ) 2020.01

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. 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.

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Allelopathic potential and identification of two allelopathic substances in Eleocharis atropurpurea

Zaman F., Iwasaki A., Suenaga K., Kato-Noguchi H.

Plant Biosystems (Plant Biosystems) 2020

ISSN 11263504

© 2020, © 2020 Societá Botanica Italiana. 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 I50 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.

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Potential use of Schumannianthus dichotomus waste: the phytotoxic activity of the waste and its identified compounds

Rob M.M., Iwasaki A., Suenaga K., Ozaki K., Teruya T., Kato-Noguchi H.

Journal of Environmental Science and Health - Part B Pesticides, Food Contaminants, and Agricultural Wastes (Journal of Environmental Science and Health - Part B Pesticides, Food Contaminants, and Agricultural Wastes) 2020

ISSN 03601234

© 2020 Taylor & Francis Group, LLC. 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 (I 50 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.

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Assessment of allelopathic potential of Dalbergia cochinchinensis Pierre and its growth inhibitory substance

Krumsri R., Iwasaki A., Suenaga K., Kato-Noguchi H.

Emirates Journal of Food and Agriculture (Emirates Journal of Food and Agriculture) 32 ( 7 ) 513 - 521 2020

ISSN 2079052X

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. I50 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.

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Garcienone, a novel compound involved in allelopathic activity of Garcinia Xanthochymus hook

Rob M.M., Iwasaki A., Suzuki R., Suenaga K., Kato-Noguchi H.

Plants (Plants) 8 ( 9 ) 2019.09

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. 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.

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Marine natural products: A source of novel anticancer drugs

Khalifa S., Elias N., Farag M., Chen L., Saeed A., Hegazy M., Moustafa M., El-Wahed A., Al-Mousawi S., Musharraf S., Chang F., Iwasaki A., Suenaga K., Alajlani M., Göransson U., El-Seedi H.

Marine Drugs (Marine Drugs) 17 ( 9 ) 2019.08

© 2019 by the authors. 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.

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Total Synthesis, Stereochemical Revision, and Biological Assessment of Iriomoteolide-2a

Sakamoto K., Hakamata A., Iwasaki A., Suenaga K., Tsuda M., Fuwa H.

Chemistry - A European Journal (Chemistry - A European Journal) 25 ( 36 ) 8528 - 8542 2019.06

ISSN 09476539

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 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.

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Kyanamide, a new Ahp-containing depsipeptide from marine cyanobacterium Caldora penicillata

Ozaki K., Iwasaki A., Suenaga K., Teruya T.

Tetrahedron (Tetrahedron) 75 ( 25 ) 3382 - 3386 2019.06

ISSN 00404020

© 2019 Elsevier 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 μM.

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Phytotoxic potential of Chrysopogon aciculatus (Retz.) Trin. (Poaceae)

Islam M., Zaman F., Iwasaki A., Suenaga K., Kato-Noguchi H.

Weed Biology and Management (Weed Biology and Management) 19 ( 2 ) 51 - 58 2019.06

ISSN 14446162

© 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.

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Phytotoxic activity of kiwifruit leaves and isolation of a phytotoxic substance

Okada S., Iwasaki A., Kataoka I., Suenaga K., Kato-Noguchi H.

Scientia Horticulturae (Scientia Horticulturae) 250 243 - 248 2019.05

ISSN 03044238

© 2019 Elsevier B.V. When aged kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) plants are replaced with young ones, the growth and productivity of the young plants were occasionally lower than expected. This symptom is typical of the replant problems reported in several fruit trees. Phytotoxic substances released from the plant are assumed to be involved in the replant problems. Although some substances contained in kiwifruit leaves have been reported to have phytotoxic activity, little is known about phytotoxicity and phytotoxic substances in kiwifruit leaves on the growth of the kiwifruit itself. Therefore, this study determined the phytotoxic activity of kiwifruit leaf extracts and soil extracts and identified a phytotoxic substance in kiwifruit leaves. Extracts of kiwifruit leaves inhibited the growth of Lepidium sativum, Lactuca sativa, Medicago sativa, Phleum pratense, Lolium multiflorum, Echinochloa crus-galli, and kiwifruit seedlings. The soil extracts also inhibited the growth of L. sativum. These results suggest that kiwifruit leaf extracts and soil extracts may possess phytotoxic substances. (-)-Epicatechin was isolated from the extracts with bioassay-guided separations using chromatography. The concentrations of (-)-epicatechin required for 50% growth inhibition of the hypocotyls and radicles of L. sativum were 27.9 and 10.7 mM, respectively, and those for the hypocotyls and radicles of kiwifruit were 13.9 and 7.6 mM, respectively. This substance may contribute to the phytotoxic activity of kiwifruit leaf extracts and may be involved in the kiwifruit replant problem.

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(+)-Isoamericanol A: A Plant Growth Inhibitor from Heliotropium indicum

Chaipon S., Boonmee S., Iwasaki A., Suenaga K., Kato-Noguchi H.

Natural Product Communications (Natural Product Communications) 14 ( 5 ) 2019.05

ISSN 1934578X

© 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.

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Allelopathic Potency and an Active Substance from Anredera cordifolia (Tenore) Steenis

Bari I., Kato-Noguchi H., Iwasaki A., Suenaga K.

Plants (Plants) 8 ( 5 ) 2019.05

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. 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.

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Phytotoxic property of Piper retrofractum fruit extracts and compounds against the germination and seedling growth of weeds

Suwitchayanon P., Ohno O., Suenaga K., Kato-Noguchi H.

Acta Physiologiae Plantarum (Acta Physiologiae Plantarum) 41 ( 3 ) 2019.03

ISSN 01375881

© 2019, Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków. The fruits of Piper retrofractum Vahl. contain a variety of compounds, but no phytotoxic compound with plant growth inhibitory activity has been reported. Therefore, the phytotoxic activity of P. retrofractum fruit extracts was investigated and found the reduction of seedling growth of cress, lettuce, alfalfa, barnyard grass, Italian ryegrass, and jungle rice. Seven bioactive compounds were isolated from the fruit extracts and identified as 3-phenylpropanoic acid (1), (2E,4E)-methyl piperate (2), (2E,4Z)-methyl piperate (3), piperlonguminine (4), dihydropiperine (5), isochavicine (6), and piperine (7). There have been no reports for their phytotoxic activity. The activity of these compounds was determined against the germination and seedling growth of cress and barnyard grass. The total germination percentage (GP) of cress was significantly inhibited by 1, 2, and 6 (40–100% inhibition), while its germination index or progressive total of cumulative germination (GI) was the most sensitive to 1, leading to the longest time required for 50% germination (T50) at 57 h behind control. However, the seedling growth of cress was highly inhibited by 6 with I50 values of 11 µM. The compounds 1 and 5–7 showed significant inhibition on GP of barnyard grass by 55–47%, while 5 and 1 effectively reduced GI and extended T50 to 42–48 h behind control, and 7 showed the most growth inhibition with I50 values of 37 µM. The inhibitory effects of the seven compounds indicate the phytotoxic property of P. retrofractum fruits, which 1, 5–7 may be the main compounds responsible for the phytotoxicity.

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Phytotoxic activity of Chinese violet (Asystasia gangetica (L.) T. Anderson) and two phytotoxic substances

Suzuki M., Chozin M., Iwasaki A., Suenaga K., Kato-Noguchi H.

Weed Biology and Management (Weed Biology and Management) 19 ( 1 ) 3 - 8 2019.03

ISSN 14446162

© 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.

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Evaluation of allelopathic competency of Lamium amplexicaule and identification of its allelopathic active substance

Sakamoto C., Suzuki M., Iwasaki A., Suenaga K., Kato-Noguchi H.

Emirates Journal of Food and Agriculture (Emirates Journal of Food and Agriculture) 31 ( 2 ) 76 - 80 2019.02

ISSN 2079052X

© 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.

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Minnamide A, a Linear Lipopeptide from the Marine Cyanobacterium Okeania hirsuta

Sumimoto S., Kobayashi M., Sato R., Shinomiya S., Iwasaki A., Suda S., Teruya T., Inuzuka T., Ohno O., Suenaga K.

Organic Letters (Organic Letters) 2019

Research paper (scientific journal), Accepted, ISSN 15237060

© 2019 American Chemical Society. 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 IC 50 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.

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Plant growth inhibitory activity of the extracts of acmella oleracea and its growth inhibitory substances

Kato-Noguchi H., Suwitchayanon P., Boonmee S., Iwasaki A., Suenaga K.

Natural Product Communications (Natural Product Communications) 14 ( 6 ) 2019

ISSN 1934578X

© 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.

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Phytotoxic activity of crop residues from Burdock and an active substance

Suzuki M., Iwasaki A., Suenaga K., Kato-Noguchi H.

ISSN 03601234

© 2019, © 2019 Taylor & Francis Group, LLC. 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.

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