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(organic chemistry)
C5H4N4O2 A toxic yellow-white purine base that is found in blood and urine, and occasionally in plants; it is a powder, insoluble in water and acids, soluble in caustic soda; sublimes when heated; used in medicine and as a chemical intermediate. Also known as dioxopurine.



(2,6-dioxopurine) an intermediate product of the metabolic degradation of purine bases. Its structural formula is

Xanthine forms yellow crystals. Its melting point is 220°C (with decomposition), and its molecular weight is 152.12. Xanthine dissolves poorly in water and better in alcohol. It displays the properties of a weak acid and a weak base. Widely found in nature (in small amounts), it is formed during the hydrolytic deamination of guanine or as a result of the aerobic oxidation of hypoxanthine in the presence of the enzyme xanthine oxidase. This enzyme also oxidizes xanthine to the final product of purine metabolism in man—uric acid—and this serves as a basis for xanthine determination. When this stage of xanthine metabolism is disrupted, xanthine accumulates in the body, primarily in the form of calcium salts (urinary calculus).

References in periodicals archive ?
Intermediate dehydrogenase oxidase form of xanthine oxidoreductase in rat liver.
Uric acid a breakdown product in ingested and endogenously synthesised purines, DNA and RNA are degraded into purine nucleotides and bases, which are then metabolised, via the action of xanthine oxidase, to xanthine and then uric acid [24].
The XO activities with xanthine as the substrate were measured spectrophotometrically with the following modifications.
Pro- and Antitumorigenic Activity of Xanthine Oxidoreductase Products
Chemicals: Xanthine oxidase, allopurinol, xanthine, hydroxylamine, N-(1-naphthyl)-ethylenediamine dihydrochloride, sulfanilic acid, ethylenediamine tetra acetate (EDTA), butylated hydroxytoluene (BHT), gallic acid, 2, 4, 6-tripyridyl-s-triazine (TPTZ), 1,1-diphenyl-2- picrylhydrazyl (DPPH), acetylthiocholine iodide, 5,5- dithiobis [2-nitro benzoic acid (DTNB) were purchased from Merck (Germany) and sigma aldrich.
The XOR can specifically bind to endothelial cells and cell-bound XOR has been reported to produce radicals, which are inaccessible to CuZn-superoxide dismutase thus, during ischemia, ATP is degenerated to xanthine and hypoxanthine, thereby increasing XOR substrate levels, which leads to increased superoxide production.
Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol.
Our results revealed that an extract prepared from the leaves of Peumus boldus exhibited moderate inhibitory activities against pancreatic lipase (PL) and xanthine oxidase (XO) but pronounced inhibitory activities on [alpha]-glucosidase.
In the literature, it has been reported that the presence of higher XO activity in ischemic tissue is due to the conversion of the xanthine dehydrogenase enzyme into XO by a calcium-mediated protease catalyst in the ischemia mediator (GRACE, 1994).
XO Determination: Xanthine oxidase enzyme activity was measured by spectrophotometric determination of absorbance level of uric acid formation from xanthine at a wave length of 293 nm and the results were expressed in terms of mIU/mg [11].
The uricosuric agent probenecid was recognized as an alternative first-line agent for urate lowering in patients who could not tolerate or had a contraindication to at least one xanthine oxidase inhibitor.