Cytotoxic yohimbine-type alkaloids from the leaves of Rauvolfia vomitoria

Two new yohimbine-type monoterpene indole alkaloids rauvine A and B ( 1 - 2 ) and six known derivatives ( 3 - 8 ) were obtained from the leaves of R. vomitoria . The structures of the two new alkaloids were determined by extensive spectroscopic analyses, 13 C NMR and ECD calculations. This is the first time to determine the absolute configurations of yohimbine-type N -oxides by quantum chemistry calculations ( 13 C NMR and ECD calculations). All the isolates were tested for their cytotoxicity against five human cancer cell lines. Compounds 1 and 3 - 8 were inactive as anticancer agents. However, compound 2 showed moderate cytotoxicity on human MCF-7 breast, SWS80 colon, and A549 lung cancer cell lines with IC 50 values of 25.5, 22.6, and 26.0 μ M, respectively.

Keywords: Apocynaceae; Cytotoxicity; Monoterpene indole alkaloids; Rauvolfia vomitoria; Yohimbine-type alkaloids.