Bufotalin is a cardiotoxic bufanolide steroid, cardiac glycoside analogue, secreted by a number of toad species; a novel anti-osteoblastoma agent. Bufotalin is a traditional Chinese medicine prepared from the dried secretion of the auricular and skin glands of Bufo bufo gargarizans Cantor. Bufotalin has drawn attentions from both cancer biologists and oncologists due to its dramatic antitumor activities. It has been shown that bufotalin inhibits cancer cell growth and induces cancer cell apoptosis in vivo and in vitro.

Darusentan is a mixture of two isomers R and S, the last enantiomer is responsible for the therapeutic properties.