Cynbungenins A-K, structurally diverse steroids with cytotoxic activity from the roots of Cynanchum bungei Decne

Abstract

Chemical investigation of the acid hydrolysate of Cynanchum bungei roots led to the isolation of eleven undescribed steroids, namely cynbungenins A-K (1–11), and seven previously described analogues (12–18). The complete structures of these compounds were elucidated using the comprehensive spectroscopic analyses and reference data. Structurally, compounds 1 and 2 represent the first example of androstane-type steroids found in the Cynanchum plants, and compounds 3–6 and 12 are characterized as pregnane-type steroids with a rare 8,14-seco-steroid core. In the cytotoxic activity assay, compound 16 displayed the strongest cytotoxic effect against MCF-7, HCT-116, HeLa, and HepG2 cancer cell lines, with IC₅₀ values of 9.98-16.42 μM, and further research indicated that it induced both apoptosis and cell cycle arrest in the G0/G1 phase in a dose-dependent manner toward HepG2 cells.