Occurrence of bufogenin conjugates in the skin of Korean toad.

The occurrence of two new bufogenin conjugates, desacetylcinobufagin 3-succinyl-L-arginine ester and cinobufagin 3-sulfate, together with two known gamabufotalitoxin homologs and resibufogein 3-sulfate, in the skin of Korean toad, Bufo bufo gargarizans CANTOR, is reported. Their structures were elucidated by degradative means and/or direct comparison with authentic samples. These bufogenin conjugates were assayed for inhibitory activity towards guinea pig heart Na+, K+-adenosine triphosphatase.