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).