A new cytotoxic indole alkaloid from Tabernaemontana inconspicua stapf.

One new indole alkaloid derivative, 5,6-dioxo-11-hydroxy voacangine (1) together with four known compounds (2-5), were isolated from the fruits of Tabernaemontana inconspicua Stapf (Apocynaceae). Their structures were determined using 1D and 2D NMR, HRESI-MS, and a comparison with the literature. The new compound was found to be cytotoxic on human breast cancer MDA-MB 231 cells with IC₅₀ values of 3.35 µM and 2.19 µM after 24 and 48 hours, respectively.