Polyphyllin I is a steroid saponin that has been found in P. polyphylla and has anticancer activity. It decreases proliferation of, and induces apoptosis in, MCF-7 and MDA-MB-231 cells (IC50s = 5 and 2.5 μM, respectively). It disrupts the mitochondrial membrane potential, activates caspase-3, and increases protein levels of the caspase-3 substrate poly(ADP-ribose) polymerase (PARP) in HepG2 and drug-resistant R-HepG2 cells. Polyphyllin I (2.05 and 2.73 mg/kg for 10 days) reduces tumor growth in an MCF-7 mouse xenograft model.
