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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 ?
Due to its methylxanthine content, mate is a proven energizer.
Bronchodilators like methylxanthines and beta adrenergic agonists are the two drugs most prominently used in the treatment of asthma.
Artificial parthenogenesis in starfish eggs: production of parthenogenetic development through suppression of polar body formation by methylxanthines.
2]-agonists, and methylxanthines, all of which are available in short-acting and long-acting preparations.
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
Mate shows central nervous system stimulant properties attributed to its content of methylxanthine alkaloids such as caffeine and is also known to contain compounds with antioxidant properties, such as phenolic acids and tannins that are the most abundant compounds in the leaves (Bastos et al.
Benign breast disease has been found to be positively correlated with both caffeine and total methylxanthine ingestion.
Jonkman and colleagues(46) also reported that caffeine (a methylxanthine derivative) increased serum theophylline concentrations by 20% to 30% and the half-life by 3 hours (from 6.
Pentoxifylline (PTX) is a methylxanthine phosphodiesterase inhibitor which reduces superoxide anions responsible for DNA apoptosis when used at a concentration of 3.
PTX increases cAMP level by a methylxanthine inhibition of phosphodiesterase and thus improves motility, capacitation and acrosome reaction (Yovich et al.