Cardenolides from the leaves of Nerium oleander

Six new cardenolides (1-6), including three 14-hydroxylated cardenolides and three 14-carbonylated cardenolides were isolated from the dried aerial parts of Nerium oleander Linn in addition to twenty-seven known compounds (7-33). Their structures were elucidated on the basis of extensive spectroscopic evidences and single-crystal X-ray diffraction analysis. Compounds 1, 4, 7-10 and 13 exhibited significant cytotoxicity against four colon cancer cell lines (HCT116, HT29, SW620, RKO), one gastric cancer cell line (GT) and one cervical cancer cell line (HeLa) in vitro.