|Molar mass||152.11 g/mol|
|1 g/ 14.5 L @ 16 °C
1 g/1.4 L @ 100 °C
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Xanthine (// or //; 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.
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.
- It is also created from xanthosine by purine nucleoside phosphorylase (PNP).
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 made in outer space.
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, 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 GI tract. Methylxanthines are metabolized by cytochrome P450 in the liver.
These drugs act as both:
- competitive nonselective 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. Xanthines are also found very rarely as constituents of nucleic acids.
|Name||R1||R2||R3||R8||IUPAC nomenclature||Found In|
|Caffeine||CH3||CH3||CH3||H||1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione||Coffee, Guarana, Yerba mate, Tea, Kola, Guayusa, Yaupon holly|
|Theobromine||H||CH3||CH3||H||3,7-dihydro-3,7-dimethyl-1H-purine-2,6-dione||Cacao (chocolate), Yerba mate, Kola, Guayusa, Yaupon holly|
|Theophylline||CH3||CH3||H||H||1,3-dimethyl-7H-purine-2,6-dione||Tea, Cacao (chocolate), Yerba mate, Kola|
|Paraxanthine||CH3||H||CH3||H||1,7-dimethyl-7H-purine-2,6-dione||Animals that have consumed caffeine|
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