Antiproliferative Triterpenoid Saponins from the Stem of Psychotria sp.

Six new triterpenoid saponins, psychotrianosides A–F ( 1 – 6 ), and two known triterpenoid saponins, psychotrianoside G ( 7 ) and ardisianoside D ( 8 ), were isolated from Psychotria sp. Their structures were determined mainly by spectroscopic methods. The cytotoxic activities of 1 – 8 against five human cancer cell lines (MDA-MB-231, MCF-7, MCF-7/ADM, HepG2, and HepG2/ADM) are reported for the first time. Psychotrianoside C ( 3 ) showed the most potent antiproliferative activity among these saponins, and the IC 50 value of 3 against MDA-MB-231 was 2.391 ± 0.161 µM. Compound 3 was also found to induce apoptosis.