Bufadienolides from the Eggs of the Toad and Their Antimelanoma Activities.

Toads produce potent toxins, named bufadienolides, to defend against their predators. Pharmacological research has revealed that bufadienolides are potential anticancer drugs. In this research, we reported nine bufadienolides from the eggs of the toad , including two new compounds ( and ). The chemical structures of and , as well as of one previously reported semisynthesized compound (), were elucidated on the basis of extensive spectroscopic data interpretation, chemical methods, and X-ray diffraction analysis. Compound is an unusual 19-norbufadienolide with rearranged A/B rings. A biological test revealed that compounds and - showed potent cytotoxic activities toward human melanoma cell line SK-MEL-1 with IC values less than 1.0 μM. A preliminary mechanism investigation revealed that the most potent compound, , could induce apoptosis via PARP cleavage, while and significantly suppressed angiogenesis in zebrafish. Furthermore, an biological study showed that , , and inhibit SK-MEL-1 cell growth significantly.