Inhibition of phospholipase Cγ1 and cancer cell proliferation by triterpene esters from Uncaria rhynchophylla

Investigation of the hooks of Uncaria rhynchophylla resulted in isolation of six phospholipase C gamma 1 (PLC gamma 1) inhibitors (1-6). The structures of these compounds were elucidated as pentacyclic triterpene esters by spectroscopic and chemical analysis. Three of them, namely uncarinic acids C (1), D (2), and E (3), are newly reported as natural products. All the compounds showed dose-dependent inhibitory activities against PLC gamma 1 in vitro with IC50 values of 9.5-44.8 mu M and inhibited the proliferation of human cancer cells with IC50 values of 0.5-6.5 mu g/mL.