Cytotoxic indole alkaloids from Tabernaemontana officinalis.

Continued interest in cytotoxic alkaloids resulted in the isolation of 37 alkaloids including 29 known monoterpenoid indole alkaloids from the aerial parts of Tabernaemontana officinalis. Of the remaining 8 alkaloids, six were bisindole alkaloids named taberdivarines A-F (1-6) and the two were monomers named taberdivarines G and H (7-8). Alkaloids 1 and 2 are voaphylline-vobasinyl type bisindole alkaloids, a structural type previously unknown, while 3-6 exhibited cytotoxicity against three human cancer cell lines HeLa, MCF-7, and SW480 with IC50 values ranging from 1.42 to 11.35 μM.