Bufadienolides and phytoecdystones from the rhizomes of Helleborus thibetanus (Ranunculaceae)

Abstract

Two new bufadienolide glycosides with an A/B trans ring structure, 14 β,16 β-dihydroxy-3 β-( β- d-glucopyranosyloxy)-5 α-bufa-20,22-dienolide ( 1), and 14 β,16 β-dihydroxy-3 β-[ β- d-glucopyranosyl-(1→4)-( β- d-glucopyranosyloxy)]-5α-bufa-20,22-dienolide ( 2), two known ecdysteroids (polypodine B and 20-hydroxyecdysone) ( 3-4), and six known bufadienolide and its glycosides with 5 β-OH (hellebrigenin, 16 β-hydroxyhellebrigenin-3-O- α- l-rhamnoside, hellebrigenin 3-O- β- d-glucoside, hellebrin, 16 β-hydroxyhellebrigenin-3-O- β- d-glucoside, and deglucohellebrin) ( 5-10) were isolated from the rhizomes of Helleborus thibetanus. The structures of compounds 1 and 2 were elucidated using various spectroscopic methods. All compounds were reported for the first time from the title plant and their chemotaxonomic significance for the genus Helleborus was discussed.