Search for Bioactive Natural Products from Unexplored Medicinal Resources

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In this study, we constructed a naturally-occurring small-molecule library using unexplored medicinal resources such as marine algae, myxomycetes, and tropical plants, and carried out a screening study searching for bioactive substances which may be expected as leading molecules for drug developments.1)Marine organisms : About 100 species of marine algae were collected at Boso Peninsula, and their extracts were examined against antimicrobial activity, Artemia salina toxicity, and collagenase inhibitory activity. Among them, a phlorotannin and an antimicrobial plastoquinone were isolated from brown algae Ishige okamurae and Sargassum yamadae, respectively. About 30 species of nudibranchs were also collected at Boso Peninsula, and new terpenoid constituents were obtained from Dermatobranchus otome.2)Myxomycetes : We studied spore germination experiments of hundreds of field-collected myxomycetes collected in Japan and succeeded in laboratory culture of plasmodia of several myxomycetes in … More a practical scale for natural products chemistry studies. As a result, we isolated pyrroloiminoquinones, polyene yellow pigments, and a peptide lactone from cultured plasmodia of Didymium iridis, Physarum rigidum, and P.melleum, respectively. A new antimicrobial naphthoquinone, new cycloanthranilylprolines, cell-cycle inhibitory bisindoles, and a cytotoxic triterpenoid aldehyde lactone were also isolated from field-collected fruit bodies of Cribraria purpurea, Fuligo candida, Tubifera casparyi, and Tubifera dimorphotheca, respectively.3)Plants : We investigated a screening program against cytotoxicity and cell-cycle inhibitory activity using almost 300 species of tropical plants extracts collected from Khon Kaen area of Thailand. Among them, we isolated a diterpene with cell-cycle inhibitory activity from Blumea glomerata (Compositae) and its absolute configuration was revised. A new cytotoxic steroidal hexasaccharaide and a series of new sesquiterpene dimers were obtained from Agave faurcroydes (Agavaceae) and Curcuma parviflora (Zingiberaceae), respectively. A new pregnane alkaloid with cytotoxic activity against vincristine-resistant murine leukemia P388 cells was isolated from Wrightia javanica (Apocynaceae). Less