New transformation pathway and cytotoxic derivatives from the acid hydrolysis of timosaponin B III

Timosaponin B III is a major bioactive steroidal saponin isolated from Anemarrhena asphodeloides Bge. To potentially discover derivatives with better biological activity, timosaponin B III was structurally modified via acid hydrolysis to yield one new (2, timopregnane A I) C₂₁ steroidal glycoside and seven known compounds. Their structures were elucidated on the basis of NMR spectroscopy and mass spectrometry. All eight compounds were evaluated for cytotoxic activity against MCF7, SW480, HepG2, and SGC7901 cell lines in vitro. As a result, compounds 6 and 7 showed significant activity (IC₅₀ 2.94-12.2 μM) against all tested cell lines. Structure-activity relationships of these compounds were investigated and the preliminary conclusions were provided. Moreover, a new transformation pathway was discovered in the acid hydrolysis of timosaponin B III for the first time.