Cytotoxic cardenolides from Streptocaulon griffithii.

A new cardenolide, 3-O-(beta-glucopyranosyl)acovenosigenin A (1), was isolated from the roots of Streptocaulon griffithii, together with eight known cardenolides, compounds 2-9. All compounds showed significant in vitro inhibition of the proliferation of the human gastrointestinal cancer cell line HGC-27, with IC50 values in the range of ca. 20-564 nM, taxol being used as positive control. Compound 1 was also found to be strongly cytotoxic against other human tumor cell lines, including A549, MCF-7, and Hela cells.