The difference between Purine and Xanthine

When used as nouns, purine means any of a class of organic heterocyclic compounds, composed of fused pyrimidine and imidazole rings, that constitute one of the two groups of organic nitrogenous bases (the other being the pyrimidines) and are components of nucleic acids, whereas xanthine means any of a group of alkaloids that include caffeine, theophylline, and theobromine as well as the parent compound, a precursor of uric acid found in many organs of the body.

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