Cytotoxic triterpenoid saponins acylated with monoterpenic acid from Pithecellobium lucidum

Three new oleanane-type triterpene saponins, named pithelucosides A-C (1-3), together with two known saponins (4, 5) were isolated from the roots of Pithecellobium lucidum. The structures of the new saponins were established on the basis of extensive 1D and 2D NMR experiments and mass spectrometry and confirmed by acid and alkaline hydrolysis. Compounds 1-5 and 7 (pro-sapogenin obtained from the mild alkaline hydrolysate of 1) were evaluated for cytotoxic activity on five human tumoral cell lines (HCT-8, Bel-7402, BGC-823, A549, and A2780) and for hemolytic property against rabbit erythrocytes. Compounds 2-5 showed significant cytotoxic activities with IC50 values of 0.61-7.56 microM. All tested compounds did not exhibit any hemolytic activity in the concentration range 0.01-100 microM.