\Xan"thine\, n. Also Xanthin \Xan"thin\ . [Gr. xanqo`s
yellow.] (Physiol. Chem.)
A white microcrystalline nitrogenous compound, {C5H4O2N4},
present in muscle tissue, in the liver, spleen, pancreas, and
other organs, and also in urine (in small quantities) and
some urinary calculi, and in the juices of certain plants; --
so called because it leaves a yellow residue when evaporated
to dryness with nitric acid. Xanthine is closely related to
uric acid.