Taccasubosides A–D, four new steroidal glycosides from Tacca subflabellata

By analyzing the steroidal content of fresh whole plants of Tacca subflabellata (Taccaceae), we isolated one sapogenin and eight glycosides with four kinds of steroidal skeletons including four new glycosides, named taccasubosides A–D (1–4), together with five known compounds. Among them, compound 1 is the first pentacyclic sterol glycoside with 6–6–6–5–6 fused rings. The structures of 1–4 were elucidated on the basis of extensive spectroscopic analysis, including that of 2D NMR data, and the results of acidic hydrolysis. The cytotoxicity of the selected steroidal glycosides (1–4, 8, and 9) was evaluated in vitro against five human cancer cell lines. Compound 9 showed significant inhibitory activity against all five cell lines.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Four new steroidal glycosides were isolated from Tacca subflabellata (Taccaceae). ► Compound 1 is the first pentacyclic steroidal glycoside with 6–6–6–5–6 fused rings. ► The cytotoxicity of the selected steroidal glycosides were evaluated in vitro against human tumor cell lines of HL-60, SMMC-7721, A549, MCF-7, and SW480. ► Compounds 8 and 9 showed cytotoxicities.