Three new cardenolides from the fruits of Cascabela thevetia (L.) Lippold and their cytotoxic activities.

Phytochemical investigations on the fruits of Cascabela thevetia (L.) Lippold led to obtain three new cardenolides ( 1 - 3 ) and five known analogues ( 4 - 7 ). Their structures were elucidated by means of UV, IR, HR-ESI-MS, 1D and 2D NMR spectroscopic data analysis. Compounds 1 and 2 represent the first examples of naturally occurring cardenolides with 19- nor -5(10)-ene group and α - l -3-demethyl-thevetose, respectively. Compound 3 is a rare C -nor- D-homocardenolide in nature. All isolated cardenolides ( 1 - 7 ) were evaluated for their cytotoxic activities against four human cancer cell lines (MCF-7, HCT-116, HeLa and HepG2), and the results indicated the compounds with sugar units ( 1 , 2 , 4 , and 5 ) exhibited stronger cytotoxic activities with IC ₅₀ values ranging between 0.022 and 0.308  μ M.