Xanthin

[Sarah]

A white microcrystalline nitrogenous compound, C5H4O2N4,present in muscle tissue, in the liver, spleen, pancreas, and otherorgans, and also in urine (in small quantities) and some urinarycalculi, and in the juices of certain plants; -- so called because itleaves a yellow residue when evaporated to dryness with nitric acid.Xanthine is closely related to uric acid.