Steroidal constituents from Helleborus thibetanus and their cytotoxicities.

Thibetanosides E–H (1–4), four new steroidal constituents including three rare sulfonates (2–4), were isolated from the roots and rhizomes of Helleborus thibetanus, together with nine known steroidal compounds (5–13). Their structures were elucidated by detailed spectroscopic analysis, including 1D and 2D NMR techniques and chemical evidence. In this study, compounds 2–13 were evaluated for their cytotoxic activities against HCT116, A549 and HepG2 tumor cell lines in vitro. Among them, compound 8 (thibetanoside C) showed cytotoxicities against A549 cells(IC50 39.6 ± 1.9 μmol·L−1) and HepG2 cells(IC50 41.5 ± 1.1 μmol·L−1), respectively. Compound 9 (23S, 24S)-24-[(O-β-D-fucopyranosyl)oxy]-3β, 23-dihydroxy-spirosta-5, 25(27)-diene-1β-ylO-(4-O-acetyl- α-L-rhamnopyranosyl)-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-α-L-arabinopyranoside) showed cytotoxicity against HCT116 cells(IC50 33.6 ± 2.1 μmol·L−1).