Studies on the Gelsemium Alkaloids for the Discovery and Development of New Antitumor Natural Products.

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To discover new antitumor natural products, we carried out the chemical investigation of the alkaloids in Gelsemium plants (Loganiaceae), and the evaluation of the cytotoxic effects of Gelsemium alkaloids on some tumor cells.By exhaustive investigation of the constituents in Gelsemium plants, eight new gelsedine-type alkaloids (gelsedilam, 14-acetoxygelsedilam, gelsefuranidine, gelseiridone, 14-acetoxygelsenicine, 14-acetoxy-15-hydroxygelsenicine, 14-hydroxy-19-oxogelsenicine, 14-acetoxygelselegine) were isolated from G. elegans. Gelsedilam and 14-acetoxygelsedilam are the first examples of 18,19-nor-type monoterpenoid indole alkaloids. Gelsefuranidine and gelseiridone have, respectively, an additional furan residue or an iridoid unit on the gelsenicine-related monoterpenoid indole alkaloid. From G. sempervirens, five new sarpagine-type alkaloids (gelsempervine-A, -B, -C, and -D, 19Z-16-epi-voacarpine) and one new yohimbane-type alkaloid (sempervilam) were isolated.The cytotoxic effects on fourteen Gelsemium alkaloids against the human squamous epithelioma cell line A431and rat hepatoma cell line H4-II-E-C3 were evaluated. Among the fourteen alkaloids, five gelsedine-type alkaloids including 14,15-dihydroxygelsenicine [EC_<50> 0.25 μM (A431)] showed strong cytotoxic effects [positive control, cisplatin, EC_<50> 3.5 μM (A431)].