Cytotoxic cardenolide glycosides from the root of Reevesia formosana.

Bioassay-guided fractionation of the root tissue of Reevesia formosana led to isolation of 13 cardenolide glycosides, reevesiosides A-I and epi-reevesiosides F-I. Their structures were determined by means of spectroscopic analysis and single-crystal X-ray diffraction was performed using reevesioside A. Reevesioside A, reevesioside F, and epi-reevesioside F displayed especially potent cytotoxicity against the MCF-7 and NCI-H460 cancer cell lines, with IC(50) values of 63±2 and 19±1, 72±8 and 20±0, and 34±6 and 10±1 nM, respectively. Identification of the sugar constituents and unusual 18,20-epoxide cardenolide glycosides are described herein. Cardiac glycosides were previously unknown in the Sterculiaceae family.