Chrysosaxillins A-E, cucurbitane triterpenoid derivatives from Chrysosplenium axillare Maxim. (Yajima) and their cytotoxic activities.

Chrysosplenium axillare Maxim. is used in traditional Tibetan medicine for the treatment of various human diseases, such as fever, headache, cholecystitis, acute icterohepatitis and acute liver necrosis. In this study, five new cucurbitane triterpenoid derivatives, chrysosaxillins A-E (1-5), along with three known structurally related compounds (6-8) have been isolated from whole herb of C. axillare. Their structures were elucidated by spectroscopic methods, including 1D and 2D NMR, HRESIMS, UV, IR, ECD and single-crystal X-ray diffraction. All isolates were evaluated for cytotoxic activities against four tumor cell lines including PC-3, A549, MCF-7, and HepG2. The results discovered that compound 1 possessed the most potent cytotoxicity against A549 cells with IC50 value of 0.05 μM, while compounds 2 and 4 have mild cytotoxicities against cells tested with IC50 values ranging from 8.78 to 41.72 μM. Our study suggests that C. axillare might serve as a valuable source of cucurbitane triterpenoids potentially useful for the development of new anti-tumor agents and support its use as a crop benefits to local economic.