Structurally diverse cucurbitane-type triterpenoids from the tubers of Hemsleya chinensis with cytotoxic activity

Abstract

Ten previously undescribed cucurbitane-type triterpenoids, namely hemslyencins A-F (1-6) and hemslyencosides A-D (7-10), together with twenty previously reported compounds (11-30), were isolated from the tubers of Hemsleya chinensis. Their structures were elucidated by unambiguous spectroscopic data (UV, IR, HR-ESI-MS, 1D and 2D NMR data). Hemslyencins A and B (1 and 2) possessing unique 9, 11-seco-ring system with a six-membered lactone moiety, were the first examples among of the cucurbitane-type triterpenoids, and hemslyencins C and D (3 and 4) and hemslyencoside D (10) are the infrequent pentacyclic cucurbitane triterpenes featuring a 6/6/6/5/6 fused system. The cytotoxic activities of all isolated compounds were evaluated against MCF-7, HCT-116, HeLa, and HepG2 cancer cells, and their structure-activity relationships (SARs) was discussed as well. Compounds 17, 25, and 26 showed significant cytotoxic effects with IC₅₀ values ranging from 1.31 to 9.89 μM, among which compound 25 induced both apoptosis and cell cycle arrest at G2/M phase in a dose dependent manner against MCF-7 cells.

Keywords: Chemical constituents; Cucurbitaceae; Cucurbitane-type triterpenoids; Cytotoxic activity; Hemsleya chinensis.