The Collaborative Dictionary

Xanthine \Xan"thine\, n. Also Xanthin \Xan"thin\ . [Gr. xanqo`s yellow.] (Physiol. Chem.) A type of purine obtainable as a white microcrystalline powder, C5H4O2N4, present in muscle tissue, in the liver, spleen, pancreas, and other organs, and also in urine (in small quantities) and some urinary calculi, and in the juices of certain plants; -- so called because it leaves a yellow residue when evaporated to dryness with nitric acid. It is also present in guano. Xanthine is closely related to uric acid. [Webster 1913 Suppl.]

Word Net

xanthine n : crystalline oxidation product of the metabolism of nucleoproteins; precursor of uric acid; found in many organs and in urine

English

Noun

1. Any of a group of alkaloids, that include caffeine, theophylline, and theobromine as well as the parent compound, a precursor of uric acid found in many organs of the body.

Usage notes

• There is much confusion between this word and xanthein, and they are often interchanged.

Translations

• Dutch: xanthine
• Finnish: ksantiini, dioksipuriini
• Italian: xantina
• Turkish: ksantin

distinguish xanthene Xanthine (), (3,7-dihydro-purine-2,6-dione), is a purine base found in most body tissues and fluids and in other organisms.

Reactions

Xanthine is a product on the pathway of purine degradation.

• It is created from guanine by guanine deaminase.
• It is created from hypoxanthine by xanthine oxidoreductase.

Xanthine is subsequently converted to uric acid by the action of the xanthine oxidase enzyme.

Pathology

People with the rare genetic disorder xanthinuria lack sufficient xanthine oxidase and cannot convert xanthine to uric acid.

Clinical significance of xanthine derivatives

Derivatives of xanthine, known collectively as xanthines, are a group of alkaloids commonly used for their effects as mild stimulants and as bronchodilators, notably in treating the symptoms of asthma. In contrast to other, more potent stimulants, they only inhibit the actions of sleepiness-inducing adenosine, making them far less effective as stimulants than sympathomimetic amines. Due to widespread effects, the therapeutic range of xanthines is narrow, making them merely a second-line asthma treatment. The therapeutic level is 10-20 micrograms/mL blood; signs of toxicity include tremor, nausea, nervousness, and tachycardia/arrhythmia.

Methylated xanthine derivatives include caffeine, paraxanthine, theophylline, and theobromine. These drugs inhibit phosphodiesterase and antagonise adenosine. Xanthines are also found very rarely as constituents of nucleic acids.

References