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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(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).

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Firstly, these compounds inhibit the xanthine oxidase activity and secondly, some of them scavenge superoxide radical.
As a result, this may not be the best theory on how xanthines exert a therapeutic effect.
In this day and age, emphasizing its identity as a Xanthine derivative would be practically a kiss of death with all anticaffeine propaganda prevalent.
Urine alkalinization to promote uric acid excretion is no longer recommended because of a lack of clear efficacy and the potential for precipitating xanthine and calcium phosphate in the renal tubules.
The xanthine oxidase inhibitor febuxostat, 80 mg/d or 120 mg/d (the latter an investigational dose but recommended by ACR and EULAR when needed) has demonstrated superior urate-lowering efficacy compared with allopurinol at a fixed dosage of 300 mg/d (table).
Human endothelial cells contain cytoplasmic and membrane-bound XO, capable of producing [O.sup.-.sub.2] and [H.sub.2][O.sub.2], depending on whether the substrate is xanthine or hypoxanthine.
Xanthine dehydrogenase and XO are two separate but interconvertible enzymes involved in oxygen radical production.
The second aim of this study is to investigate the xanthine oxidase, tyrosinase, elastase, and neuraminidase inhibition effect of these S-substituted perhalonitrobuta-1,3-diene compounds.
The activity of xanthine oxidase was calculated using the production of uric acid via xanthine through a spectrophotometry elevation at 293 nm.
The plant contains xanthine alkaloids, saponins, chlorogenic acid, vitamins and 15 amino acids.