Chemical constituents from the roots of Cynanchum paniculatum and their cytotoxic activity

Two new steroidal saponins, cynanside A (1) and B (2) were isolated together with three known compounds (3–5) from the roots of Cynanchum paniculatum (Bunge) Kitag. The structures of 1 and 2 were elucidated on the basis of spectroscopic analyses, including extensive 2D NMR and acid hydrolysis. We evaluated the cytotoxicity of isolates (1–5) against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines in vitro using the SRB bioassay. Compounds 1 and 2 showed selective cytotoxicity against SK-MEL-2 cells with IC50 values of 26.55 and 17.36 μM, respectively.