A series of heterocyclic compounds that are variously substituted in nature and are known also as purine bases. They include adenine and guanine, constituents of nucleic acids, as well as many alkaloids such as caffeine and theophylline. Uric acid is the metabolic end product of purine metabolism. ... (12 Dec 1998) ... 
These are waste products or metabolites of nucleoproteins. They are not recycleable and are broken down further to the primary excretable form, uric acid.
nitrogenous bases containing a double-ring structure with a six-carbon ring fused to a five-carbon ring; includes adenine and guanine
components of certain foods that metabolize into uric acid in the body.