Cytotoxic Cardiac Glycoside Constituents of Vallaris glabra Leaves.

Thirteen cardenolide glycosides (1-13) were isolated from the CH2Cl2 and MeOH extracts of Vallaris glabra leaves. The structures of the new compounds (2-13) were identified by spectroscopic methods, with the absolute configurations of the sugar moieties determined by acid hydrolysis. All compounds were evaluated for their cytotoxic activity against human cervix adenocarcinoma, lung carcinoma, and colorectal adenocarcinoma cell lines. The two most potent compounds [2'-O-acetylacoschimperoside P (1) and oleandrigenin-3-O-α-l-2'-O-acetylvallaropyranoside (2)] exhibited IC50 values in the range of 0.03-0.07 μM.