A<unk>  is any substance that inhibits the activity of<unk><unk> , an enzyme involved in purine metabolism. In humans, inhibition of<unk><unk>  reduces the production of uric acid, and several medications that inhibit<unk><unk>  are indicated for treatment of hyperuricemia and related medical conditions including gout.<unk> s are being investigated for management of reperfusion injury.<unk> s are of two kinds: purine analogues and others. Purine analogues include allopurinol, oxypurinol, and tisopurine. Others include febuxostat, topiroxostat, and inositols (phytic acid and myo-inositol). In experiments, numerous natural products have been found to inhibit<unk><unk>  in vitro or in model animals (mice, rats). These include three flavonoids that occur in many different fruits and vegetables: kaempferol, myricetin, and quercetin. More generally, planar flavones and flavonols with a 7-hydroxyl group inhibit<unk><unk> . An essential oil extracted from Cinnamomum osmophloeum inhibits<unk><unk>  in mice. The natural product propolis from selected sources inhibits<unk><unk>  in rats; the specific substance responsible for this inhibition has not been identified, and the generality of these findings is unknown. An extract of leaves of Pistacia integerrima also inhibits<unk><unk>  at a level that appears to merit further research. In folk medicine the tree fern Cyathea spinulosa (formerly Alsophila spinulosa) has been used for gout, but its most active component, caffeic acid, is only a weak inhibitor of<unk><unk> .
Xanthine oxidase inhibitor
Topoisomerase inhibitor
Protease inhibitor 
Exopeptidase inhibitor
Antimetabolite
Endopeptidase inhibitor
Carbonic anhydrase inhibitor
Lipase inhibitors