Isolation and characterization of uricine from uric acid stones

Uricine was found to be present in all uric acid stones tested, although another physiochemically related pigment was occasionally present. Uricine is of low molecular weight (28.2) and a preliminary analysis of its structure suggests that it is formed by two pyrrolic rings. It is a yellow pigment whose color is pH-dependent, shifting from reddish-yellow to green at pH 1.0. It is water soluble, but its solubility increases in alkaline solutions. Preliminary evidence suggests that uricine is related metabolically to bilirubin-like compounds.