ECHA InfoCard 100.000.653
C 5H 4N 4O 2
1 g/ 14.5 L @ 16 °C 1 g/1.4 L @ 100 °C
Except where otherwise noted, data are given for materials in their
(at 25 °C [77 °F], 100 kPa).
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Xanthine ( or ; archaically xanthic acid; systematic name 3,7-dihydropurine-2,6-dione) is a purine base found in most human body tissues and fluids and in other organisms. Several  stimulants are derived from xanthine, including caffeine and theobromine.
Xanthine is a product on the pathway of
Xanthine is subsequently converted to
uric acid by the action of the xanthine oxidase enzyme.
Use and manufacturing
Xanthine is used as a
drug precursor for human and animal medications, and is manufactured as a pesticide ingredient.
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 or influenza symptoms. In contrast to other, more potent stimulants like  sympathomimetic amines, xanthines mainly act to oppose the actions of adenosine, and increase alertness in the central nervous system.
Due to widespread effects, the
therapeutic range of xanthine is narrow, making it 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, theobromine, and theophylline, affect not only the airways but stimulate heart rate, force of contraction, and 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  gastrointestinal tract. Methylxanthines are metabolized by  cytochrome P450 in the liver.
If swallowed, inhaled, or exposed to the eyes in high amounts, xanthines can be harmful, and may cause an
allergic reaction if applied topically.
in vitro pharmacological studies, xanthines act as both:
phosphodiesterase inhibitors which raise intracellular cAMP, activate PKA, inhibit TNF-α  and  leukotriene synthesis, and  reduce inflammation and innate immunity and  nonselective adenosine receptor antagonists 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.     
1 = R 2 = R 3 = H Caffeine: R 1 = R 2 = R 3 = CH 3 Theobromine: R 1 = H, R 2 = R 3 = CH 3 Theophylline: R 1 = R 2 = CH 3, R 3 = H
Examples of xanthine derivatives
IUPAC nomenclature Found in
CH 3 H
H-purine-2,6(3 H,7 H)-dione Coffee, guarana, yerba mate, tea, kola, guayusa, holly
CH 3 H
H-purine-2,6-dione Cacao ( chocolate), yerba mate, kola, guayusa, holly
CH 3 H
H-purine-2,6-dione Tea, cacao ( chocolate), yerba mate, kola
CH 3 H
CH 3 H
H-purine-2,6-dione Animals that have consumed caffeine
CH 3 H
Synthetic pharmaceutical ingredient
3H 7O 2
Synthetic pharmaceutical ingredient
4H 9 H
Byproduct of purine nucleotides metabolism and a normal component of urine
People with the rare
genetic disorders, specifically xanthinuria and Lesch-Nyhan syndrome, lack sufficient xanthine oxidase and cannot convert xanthine to uric acid.
Speculation on origin
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.  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 found in outer space.  
Merck Index, 11th Edition, 9968.
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