- a crystalline, nitrogenous compound, C5H4N4O2, related to uric acid, occurring in urine, blood, and certain animal and vegetable tissues.
- any derivative of this compound.
- a crystalline compound related in structure to uric acid and found in urine, blood, certain plants, and certain animal tissues. Formula: C 5 H 4 N 4 O 2
- any substituted derivative of xanthine, esp one of the three pharmacologically active methylated xanthines, caffeine, theophylline, or theobromine, which act as stimulants and diuretics
