In experiments, numerous natural products have been found to inhibit xanthine oxidase in vitro or in model animals (mice, rats). These include three flavonoids that occur in many different fruits and vegetables: kaempferol, myricetin, and quercetin.[4][5] More generally, planar flavones and flavonols with a 7-hydroxyl group inhibit xanthine oxidase.[6] An essential oil extracted from Cinnamomum osmophloeum inhibits xanthine oxidase in mice.[7] The natural product propolis from selected sources inhibits xanthine oxidase in rats; the specific substance responsible for this inhibition has not been identified, and the generality of these findings is unknown.[8] An extract of leaves of Pistacia integerrima also inhibits xanthine oxidase at a level that appears to merit further research.[9]
^Iwanaga T, Kobayashi D, Hirayama M, Maeda T, Tamai I (December 2005). "Involvement of uric acid transporter in increased renal clearance of the xanthine oxidase inhibitor oxypurinol induced by a uricosuric agent, benzbromarone". Drug Metabolism and Disposition. 33 (12): 1791–5. doi:10.1124/dmd.105.006056. PMID16135657. S2CID16377221.
^Becker MA, Schumacher HR, Wortmann RL, et al. (March 2005). "Febuxostat, a novel nonpurine selective inhibitor of xanthine oxidase: a twenty-eight-day, multicenter, phase II, randomized, double-blind, placebo-controlled, dose-response clinical trial examining safety and efficacy in patients with gout". Arthritis and Rheumatism. 52 (3): 916–23. doi:10.1002/art.20935. PMID15751090.
^Selloum L, Reichl S, Müller M, Sebihi L, Arnhold J (November 2001). "Effects of flavonols on the generation of superoxide anion radicals by xanthine oxidase and stimulated neutrophils". Archives of Biochemistry and Biophysics. 395 (1): 49–56. doi:10.1006/abbi.2001.2562. PMID11673865.
^Ahmad NS, Farman M, Najmi MH, Mian KB, Hasan A (May 2008). "Pharmacological basis for use of Pistacia integerrima leaves in hyperuricemia and gout". J Ethnopharmacol. 117 (3): 478–82. doi:10.1016/j.jep.2008.02.031. PMID18420362.
^Chiang HC, Lo YJ, Lu FJ (1994). "Xanthine oxidase inhibitors from the leaves of Alsophila spinulosa (Hook) Tryon". Journal of Enzyme Inhibition. 8 (1): 61–71. doi:10.3109/14756369409040777. PMID7539070.
