The pigments in the dorsal skin of frogs.

The five pigments 1-5 and a colorless substance 6 were present in the dorsal skin of frogs of nine selected species belonging to Rhacophoridae, Ranidae, Hylidae, and Bufonidae and were identified as pterin-6-carboxylic acid, xanthopterin, isoxanthopterin, erythro-biopterin, 6-hydroxymethylpterin, and guanine, respectively. Another pigment 7 was specifically present in the skin of genus Rhacophorus and was deduced to be a pteridine derivative composed of five molecules of pterin-6-carboxylic acid [1].