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 (IC(50) values, 0.054-1.6 microM) and A549 (IC(50), 0.016-0.65 microM) 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.