New cytotoxic bufadienolides from the roots and rhizomes of Helleborus thibetanus Franch

Three new bufadienolides 14β, 16β-dihydroxy-3β-[β-D-glucopyranosyl-(1→6)-(β-D-glucopyranosyl)oxy]-5α-bufa-20, 22-dienolide (1), 14β-hydroxy-3β-[β-D-glucopyranosyl-(1→4)-(β-D-glucopyranosyl)oxy]-5α-bufa-20, 22-dienolide (2) and hellebrigenin-3-O-β-D-glucosyl-(1→4)-β-D-glucoside (3), together with eight known bufadienolides (4-11) were isolated from the roots and rhizomes of Helleborus thibetanus. Their structures were elucidated by extensive spectroscopic methods and acid hydrolysis. Compounds 1-7 were evaluated for their cytotoxic activity against HCT116, A549 and HepG2 tumor cell lines. Compound 1 exhibited moderate cytotoxicity against HepG2 cells with IC₅₀ value of 15.1 ± 1.72 μM. Compounds 5 and 6 exhibited moderate cytotoxicity against HCT116 cells with IC₅₀ values of 15.12 ± 0.58 μM and 13.17 ± 2.34 μM, respectively.

Helleborus thibetanus Franch; bufadienolide glycosides; cytotoxic activity; structure identification.