Biologically active substances from amphibians: preliminary studies on anurans from twenty-one genera of Thailand.

Amphibian skin has been the source of a wide variety of biologically active substances, but less than one-third of the known genera of amphibians have been probed for such active substances. Skins of 21 genera of anurans from Thailand have now been investigated for noxious secretions, toxic substances, and alkaloids. Four genera of bufonid toads (Bufo, Ansonia, Leptophryne, Pedostipes) were toxic due to the presence of bufadienolides or bufadienolide-like compounds. Two species of ranid frogs (Rana raniceps, Rana signata) were toxic, perhaps due to the presence of toxic peptide(s). Two species of rhacophorid frogs (Polypedates) were slightly noxious/toxic. One species of microhylid frog (Kaloula pulchra) was noxious. Trace amounts of pumiliotoxin alkaloids were detected in a ranid frog (Limnonectes kuhli). A further 18 species did not exhibit noxious or toxic properties to a significant extent.