Xanthine is a purine base found in most body tissues and fluids, certain plants, and some urinary calculi. [1]
It is an intermediate in the degradation of adenosine monophosphate to uric acid, being formed by oxidation of hypoxanthine. Thus, inhibition of xanthine oxidase, by drugs such as allopurinol is a treatment for gout, caused by increases of uric acid crystals in tissue.
The methylxanthines caffeine, theobromine, and theophylline and their derivatives are used in medicine for their bronchodilator and stimulant effects.