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Title: Methylxanthine  
Author: World Heritage Encyclopedia
Language: English
Subject: Ephedrine
Publisher: World Heritage Encyclopedia


Not to be confused with xanthene or the xanthophylls whose names end with "-xanthin".
Template:Chembox ChEMBL
CAS number 69-89-6 YesY= ?
PubChem 1188
ChemSpider 1151 YesY
DrugBank DB02134
KEGG C00385 YesY
ChEBI CHEBI:17712 YesY
Jmol-3D images Image 1
Molecular formula C5H4N4O2
Molar mass 152.11 g/mol
Appearance White solid
Melting point


Solubility in water 1 g/ 14.5 L @ 16 °C
1 g/1.4 L @ 100 °C
NFPA 704
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Xanthine (/ˈzænθn/ or /ˈzænθn/; archaically xanthic acid) (3,7-dihydro-purine-2,6-dione), is a purine base found in most human body tissues and fluids and in other organisms. A number of stimulants are derived from xanthine, including caffeine and theobromine.[1]

Xanthine is a product on the pathway of purine degradation.

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

Studies reported in 2008, based on 12C/13C isotopic ratios of organic compounds found in the Murchison meteorite, suggested that xanthine and related chemicals, including the RNA component uracil, were formed extraterrestrially.[3][4] In August 2011, a report, based on NASA studies with meteorites found on Earth, was published suggesting xanthine and related organic molecules, including the DNA and RNA components adenine and guanine, were made in outer space.[5][6][7]


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 the treatment of asthma symptoms. In contrast to other, more potent stimulants like sympathomimetic amines, xanthines mainly act to oppose the actions of the sleepiness-inducing adenosine, and increase alertness in the central nervous system. They also stimulate the respiratory centre, and are used for treatment of infantile apnea. 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 xanthines (methylxanthines), which include caffeine, aminophylline, IBMX, paraxanthine, pentoxifylline,[8] theobromine, and theophylline, affect not only the airways but stimulate heart rate, force of contraction, cardiac arrhythmias at high concentrations. In high doses they can lead to convulsions that are resistant to anticonvulsants. Methylxanthines induce acid and pepsin secretions in the GI tract. Methylxanthines are metabolized by cytochrome P450 in the liver.

These drugs act as both:

  1. competitive nonselective phosphodiesterase inhibitors [9] which raise intracellular cAMP, activate PKA, inhibit TNF-alpha [8][10] and leukotriene [11] synthesis, and reduce inflammation and innate immunity [11] and
  2. nonselective adenosine receptor antagonists [12] which inhibit sleepiness-inducing adenosine.

But different analogues show varying potency at the numerous subtypes, and a wide range of synthetic xanthines (some nonmethylated) have been developed searching for compounds with greater selectivity for phosphodiesterase enzyme or adenosine receptor subtypes.[13][14][15][16][17][18][19][20][21][22][23][24][25] Xanthines are also found very rarely as constituents of nucleic acids.

Selected Xanthines
Name R1 R2 R3 R8 IUPAC nomenclature Found In
Xanthine H H H H 3,7-dihydro-purine-2,6-dione plants, animals
Caffeine CH3 CH3 CH3 H 1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione Coffee, Guarana, Yerba mate, Tea, Kola
Theobromine H CH3 CH3 H 3,7-dihydro-3,7-dimethyl-1H-purine-2,6-dione Chocolate, Yerba mate
Theophylline CH3 CH3 H H 1,3-dimethyl-7H-purine-2,6-dione Tea, chocolate, Yerba mate
Paraxanthine CH3 H CH3 H 1,7-dimethyl-7H-purine-2,6-dione Animals that have consumed caffeine
8-Chlorotheophylline CH3 CH3 H Cl Dimenhydrinate

See also


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