Antiproliferative activity of cardenolides isolated from streptocaulon juventas

Sixteen cardenolides, two hemiterpenoids, two phenylpropanoids and a phenylethanoid isolated from the roots of Streptocaulon juventas (LOUR.) MERR. were examined for their antiproliferative activity toward three human-derived (HT-1080 fibrosarcoma, lung A549 adenocarcinoma, cervix HeLa adenocarcinoma) and three murine-derived (colon 26-L5 carcinoma, Lewis lung carcinoma, B16-BL6 melanoma) cell lines. The cardenolides selectively and strongly inhibited proliferation of the HT-1080 (IC50 values, 0.054-1.6 mum) and A549 (IC50, 0.016-0.65 mum) cell lines. The characteristic morphological changes and ladder-like DNA fragmentation in those cells treated with the cardenolides indicated the antiproliferative activity was due to the induction of apoptosis.