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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 ?
There are three classes of bronchodilators: anticholinergics, methylxanthines, and beta adrenergic agonists.
SABA, Inhaled SAMA, single combination inhaler of SABA + SAMA, Inhaled LABA, Inhaled LAMA, combination inhaler of ICS + LABA, Phosphodiesterase-4 (PDE-4) inhibitor, oral corticosteroids, methylxanthine, antibiotics, alpha-1 antitrypsin augmentation therapy
Chocolate contains a chemical called methylxanthine from the cocoa tree, which is similar to caffeine.
Pentoxifylline (PTX) is a methylxanthine phosphodiesterase inhibitor which reduces superoxide anions responsible for DNA apoptosis when used at a concentration of 3.
Benign breast disease has been found to be positively correlated with both caffeine and total methylxanthine ingestion.
Keeping Chocolate Away from Pets VPI received 1,016 methylxanthine (chocolate toxicity) claims in 2012.
coli strains equipped with a new synthetic N-demethylation operon could be useful for reclaiming nutrient-rich byproducts of coffee bean processing and for cost-effective bioproduction of methylxanthine drugs.
PTX increases cAMP level by a methylxanthine inhibition of phosphodiesterase and thus improves motility, capacitation and acrosome reaction (Yovich et al.