Ochroborbone, A New Cytotoxic Indole Alkaloid from Ochrosia borbonica

A new monoterpenoid indole alkaloid, ochroborbone (1), along with five known alkaloids (2-6), were isolated from the stems and leaves of Ochrosia borbonica. Among them, ochroborbone (1) is a rare C17-nor monoterpenoid indole alkaloid, and the known compounds (2-6) were isolated from Ochrosia for the first time-These structures were established on the basis of extensive spectroscopic methods. All isolated compounds were evaluated for their cytotoxicities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480 in vitro. Compounds 1 and 2 exhibited inhibitory effects with IC₅₀ values comparable with those of cisplatin.