Conformational Preference of Two Toad Poison Bufadienolides, Cinobufagin and Bufotalin

Abstract

The solution state conformations of pyran-2-one ring (E ring) of two toad poison bufadienolides, cinobufagin and bufotalin, were analyzed by using NOE experiments at low temperatures and molecular dynamics simulation study. The rotation of E ring of the two bufadienolides, was found to be affected by the 14β,15β-epoxy and 16β-acetoxy groups and to be restricted at low temperatures. In the experimental, cinobufagin and bufotalin were isolated from Ch'an Su by the new chromatographic methods using the hydrophobic gel sephadex LH-20 and HP-cellulofine as carriers.