Studies on cardiotonic steroids from the skin of Japanese toad.

Abstract

The isolation and characterization of the cardiotonic steroid constituents in the skin of the Japanese toad, Bufo vulgaris formosus was carried out. Three new types of bufotoxins in which the succinoyl, adipoyl and pimeloyl groups are displaced for the suberoyl residue of the so-called bufotoxin, were separated and identified. The occurrence of bufogenin 3-sulfates and analogous conjugates of cardenolide named cardenobufotoxin was also demonstrated. The ethanolic extract of the skin obtained from 1800 toads was separated by chromatography on Amberlite XAD-2 resin, silica gel and Sephadex LH-20, followed by high-performance liquid chromatography to provide new cardiotonic steroid conjugates. The structures of these substances were shown to be resibufogenin 3-succinoylarginine ester, gamabufotalitoxin homologs, bufalitoxin homologs, cinobufotoxin homologs, arenobufotoxin, cinobufotalitoxin, cardenobufotoxins, bufogenin 3-sulfates and sarmentogenin 3-sulfate by degradative and synthetic means.