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.