Tabernaemontana sphaerocarpa Blume and T. elegans Staph. are a member of the Apocynaceae family that occur in Indonesia, and are found mostly in Java. Traditionally, the leaves have been used as a laxative, the flowers as a cardiotonic agent, and the latex for removing warts. Tabernaemontana species so far have been shown to produce various skeletal alkaloids, including iboga-type alkaloids such as ibogamine, aspidosperma-type alkaloids such as taberhanine, and vobasinyl-ibogan bisindole alkaloids such as conodiparine A. In our search for structually and biogenetically interesting alkaloids from tropical plants found in Indonesia, novel tetrakis-monoterpene indole alkaloid, alasmontamine A, consisting of bis-vobtusine type skeleton, and two new bis-monoterpene indole alkaloids, biscarpamontamine A, having an aspidosperma-iboga type skeleton, and biscarpamontamine B, based on aspidosperma-aspidosperma type skeleton, were isolated from Tabernaemontana elegans and T. sphaerocarpa, respectively, together with vobtusine, vobtusine lactone, 3-hydroxyvobtusine, ibogamine, voacangine, 3-hydroxyvoacangine, and vobasine. The structures of alasmontamine A and biscarpamontamines A and B were determined by 1D & 2D-NMR data (^1H-^1H COSY, HSQC, HMBC, NOESY, TOCSY) and CD spectra. Five bis-monoterpene indole alkaloids isolated in this research was evaluated for cytotoxicity against five human cancer cell lines, HL60, RPMI8226, NCI-H226, HCT116, and MCF7. As a result of analysis of cytotoxicity mechanism against HL60 cells, vobtusine was found to induce apoptosis via the caspasse-dependent pathway.
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