Template:Distinguish Template:Chembox Xanthine (Template:IPAc-en or Template:IPAc-en, from Ancient Greek {{#invoke:Lang|lang}} {{#invoke:Lang|lang}} Template:Gloss for its yellowish-white appearance; archaically xanthic acid; systematic name 3,7-dihydropurine-2,6-dione) is a purine base found in most human body tissues and fluids, as well as in other organisms.<ref name="pubchem">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Several stimulants are derived from xanthine, including caffeine, theophylline, and theobromine.<ref name="isbn0-8493-2647-8">Template:Cite book</ref><ref name=":0">Template:Cite book</ref>
Xanthine is a product on the pathway of purine degradation.<ref name=pubchem/>
- 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.
Xanthine is subsequently converted to uric acid by the action of the xanthine oxidase enzyme.<ref name=pubchem/>
Use and productionEdit
Xanthine is used as a drug precursor for human and animal medications, and is produced as a pesticide ingredient.<ref name=pubchem/>
Clinical significanceEdit
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.<ref name=pubchem/> 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.<ref name=pubchem/>
ToxicityEdit
Methylxanthines (methylated xanthines), which include caffeine, aminophylline, IBMX, paraxanthine, pentoxifylline, theobromine, theophylline, and 7-methylxanthine (heteroxanthine), among others, affect the airways, increase heart rate and force of contraction, and at high concentrations can cause cardiac arrhythmias.<ref name=pubchem/> In high doses, they can lead to convulsions that are resistant to anticonvulsants.<ref name=pubchem/> Methylxanthines induce gastric acid and pepsin secretions in the gastrointestinal tract.<ref name=pubchem/> Methylxanthines are metabolized by cytochrome P450 in the liver.<ref name=pubchem/>
If swallowed, inhaled, or exposed to the eyes in high amounts, xanthines can be harmful, and they may cause an allergic reaction if applied topically.<ref name=pubchem/>
PharmacologyEdit
Caffeine: R1 = R2 = R3 = CH3
Theobromine: R1 = H, R2 = R3 = CH3
Theophylline: R1 = R2 = CH3, R3 = H
In in vitro pharmacological studies, xanthines act as both competitive nonselective phosphodiesterase inhibitors and nonselective adenosine receptor antagonists. Phosphodiesterase inhibitors raise intracellular cAMP, activate PKA, inhibit TNF-α synthesis,<ref name=pubchem/><ref name="pmid9927365">Template:Cite journal</ref><ref name=":0" /> and leukotriene<ref name="LT-Peters-Golden">Template:Cite journal</ref> and reduce inflammation and innate immunity.<ref name="LT-Peters-Golden"/> Adenosine receptor antagonists<ref name="pmid3588607"/> inhibit sleepiness-inducing adenosine.<ref name=pubchem/>
However, 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.<ref name=pubchem/><ref name="pmid3806581">Template:Cite journal</ref><ref name="pmid3588607">Template:Cite journal</ref><ref name="pmid1658821">Template:Cite journal</ref><ref name="pmid17668454">Template:Cite journal</ref><ref name="pmid18181659">Template:Cite journal</ref>
| Name | R1 | R2 | R3 | R8 | IUPAC nomenclature | Found in |
|---|---|---|---|---|---|---|
| Xanthine | H | H | H | H | 3,7-Dihydro-purine-2,6-dione | Plants, animals |
| 7-Methylxanthine | H | H | CH3 | H | 7-methyl-3H-purine-2,6-dione | Metabolite of caffeine and theobromine |
| Theobromine | H | CH3 | CH3 | H | 3,7-Dihydro-3,7-dimethyl-1H-purine-2,6-dione | Cacao (chocolate), yerba mate, kola, guayusa |
| 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 |
| Caffeine | CH3 | CH3 | CH3 | H | 1,3,7-Trimethyl-1H-purine-2,6(3H,7H)-dione | Coffee, guarana, yerba mate, tea, kola, guayusa, Cacao (chocolate) |
| 8-Chlorotheophylline | CH3 | CH3 | H | Cl | 8-Chloro-1,3-dimethyl-7H-purine-2,6-dione | Synthetic pharmaceutical ingredient |
| 8-Bromotheophylline | CH3 | CH3 | H | Br | 8-Bromo-1,3-dimethyl-7H-purine-2,6-dione | Pamabrom diuretic medication |
| Diprophylline | CH3 | CH3 | C3H7O2 | H | 7-(2,3-Dihydroxypropyl)-1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione | Synthetic pharmaceutical ingredient |
| IBMX | CH3 | C4H9 | H | H | 1-Methyl-3-(2-methylpropyl)-7H-purine-2,6-dione | |
| Uric acid | H | H | H | O | 7,9-Dihydro-1H-purine-2,6,8(3H)-trione | Byproduct of purine nucleotides metabolism and a normal component of urine |
PathologyEdit
People with rare genetic disorders, specifically xanthinuria and Lesch–Nyhan syndrome, lack sufficient xanthine oxidase and cannot convert xanthine to uric acid.<ref name=pubchem/>
Possible formation in absence of lifeEdit
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, have been formed extraterrestrially.<ref name="Murch_base">Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Callahan">Template:Cite journal</ref><ref name="Steigerwald">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="DNA">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
See alsoEdit
ReferencesEdit
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