Water soluble skin secretions of six common Chinese amphibians were studied for their biological and enzymatic activities.The skin secretions of Tylototriton verrucosus,Bombina maxima ,and Bufo andrewsi were found toxic to mice with the intraperitoneal LD 50 of 11 5?mg/kg,18 8?mg/kg,and 264?mg/kg,respectively.No acute lethal toxicities were observed for the skin secretions of Rana nigromaculata,Rana guentheri and Rana limnocharis in a dose up to 500?mg/kg.The lethal toxicities of the skin secretions of T verrucosus and B maxima to mice are in the same grade as those of Viperidae snake venoms.The toxic components in T verrucosus and B maxima skin secretions are the proteins with molecular weights ranging from 3 to 60?kDa.All the skin secretions had both proteolytic activity and trypsin inhibitory activity.The skin secretions from T verrucosus , B maxima and B andrewsi also displayed wide spectrum antimicrobial activity.On the other hand,the skin secretions from B andrewsi and B maxima showed cytotoxicity on human cancer cells.All the six samples had not significant effects on mammalian blood coagulation system.Phospholipase A 2 activity was only found in the skin secretions of T verrucosus .None of these skin secretions showed acetylcholine esterase activity.
