xanthine

Xanthine is used as a drug precursor for human and animal medications, and is produced 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.

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. In high doses, they can lead to convulsions that are resistant to anticonvulsants. Methylxanthines induce gastric 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 they may cause an allergic reaction if applied topically.

===Pharmacology===

File:Methylxanthine.png

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,{{cite journal |vauthors=Marques LJ, Zheng L, Poulakis N, Guzman J, Costabel U |title=Pentoxifylline inhibits TNF-alpha production from human alveolar macrophages |journal=Am. J. Respir. Crit. Care Med. |volume=159 |issue=2 |pages=508–11 |date=February 1999 |pmid=9927365 |doi= 10.1164/ajrccm.159.2.9804085}} and leukotriene{{cite journal |vauthors=Peters-Golden M, Canetti C, Mancuso P, Coffey MJ | title=Leukotrienes: underappreciated mediators of innate immune responses | journal=J. Immunol. | year=2005 | pages=589–94 | volume=174 | issue=2 | pmid=15634873 | doi=10.4049/jimmunol.174.2.589| doi-access=free }} and reduce inflammation and innate immunity. Adenosine receptor antagonists inhibit sleepiness-inducing adenosine.

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.{{cite journal |vauthors=Daly JW, Padgett WL, Shamim MT | title = Analogues of caffeine and theophylline: effect of structural alterations on affinity at adenosine receptors | journal = Journal of Medicinal Chemistry | volume = 29 | issue = 7 | pages = 1305–8 |date=July 1986 | pmid = 3806581 | doi = 10.1021/jm00157a035}}{{cite journal |vauthors=Daly JW, Jacobson KA, Ukena D | title = Adenosine receptors: development of selective agonists and antagonists | journal = Progress in Clinical and Biological Research | volume = 230 | pages = 41–63 | year = 1987 | pmid = 3588607 }}{{cite journal |vauthors=Daly JW, Hide I, Müller CE, Shamim M | title = Caffeine analogs: structure-activity relationships at adenosine receptors | journal = Pharmacology | volume = 42 | issue = 6 | pages = 309–21 | year = 1991 | pmid = 1658821 | doi = 10.1159/000138813| url = https://zenodo.org/record/1235428}}{{cite journal |vauthors=González MP, Terán C, Teijeira M | title = Search for new antagonist ligands for adenosine receptors from QSAR point of view. How close are we? | journal = Medicinal Research Reviews | volume = 28 | issue = 3 | pages = 329–71 |date=May 2008 | pmid = 17668454 | doi = 10.1002/med.20108 | s2cid = 23923058 }}{{cite journal |vauthors=Baraldi PG, Tabrizi MA, Gessi S, Borea PA | title = Adenosine receptor antagonists: translating medicinal chemistry and pharmacology into clinical utility | journal = Chemical Reviews | volume = 108 | issue = 1 | pages = 238–63 |date=January 2008 | pmid = 18181659 | doi = 10.1021/cr0682195 }}

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People with rare genetic disorders, specifically xanthinuria and Lesch–Nyhan syndrome, lack sufficient xanthine oxidase and cannot convert xanthine to uric acid.

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.{{Cite journal | last1 = Martins | first1 = Z. | last2 = Botta | first2 = O. | last3 = Fogel | first3 = M. L. | last4 = Sephton | first4 = M. A. | last5 = Glavin | first5 = D. P. | last6 = Watson | first6 = J. S. | last7 = Dworkin | first7 = J. P. | last8 = Schwartz | first8 = A. W. | last9 = Ehrenfreund | first9 = P. | title = Extraterrestrial nucleobases in the Murchison meteorite | doi = 10.1016/j.epsl.2008.03.026 | journal = Earth and Planetary Science Letters | volume = 270 | issue = 1–2 | pages=130–136 | year = 2008 | bibcode=2008E&PSL.270..130M|arxiv = 0806.2286 | s2cid = 14309508 }}{{Cite web|author=AFP Staff |title=We may all be space aliens: study |date=13 June 2008 |url=http://afp.google.com/article/ALeqM5j_QHxWNRNdiW35Qr00L8CkwcXyvw |publisher=AFP |access-date=2011-08-14 |url-status=dead |archive-url=https://web.archive.org/web/20080617213441/http://afp.google.com/article/ALeqM5j_QHxWNRNdiW35Qr00L8CkwcXyvw |archive-date=June 17, 2008 }} 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.{{Cite journal | last1 = Callahan | first1 = M. P. | last2 = Smith | first2 = K. E. | last3 = Cleaves | first3 = H. J. | last4 = Ruzicka | first4 = J. | last5 = Stern | first5 = J. C. | last6 = Glavin | first6 = D. P. | last7 = House | first7 = C. H. | last8 = Dworkin | first8 = J. P. | doi = 10.1073/pnas.1106493108 | title = Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases | journal = Proceedings of the National Academy of Sciences | volume = 108 | issue = 34 | pages = 13995–8 | year = 2011 | pmid = 21836052| pmc = 3161613| bibcode = 2011PNAS..10813995C | doi-access = free }}{{cite web |last=Steigerwald |first=John |title=NASA Researchers: DNA Building Blocks Can Be Made in Space |url=http://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html |publisher=NASA |date=8 August 2011 |access-date=2011-08-10 }}{{cite web |author=ScienceDaily Staff |title=DNA Building Blocks Can Be Made in Space, NASA Evidence Suggests |url=https://www.sciencedaily.com/releases/2011/08/110808220659.htm |date=9 August 2011 |website=ScienceDaily |access-date=2011-08-09}}

• DMPX
• Murchison meteorite
• Theobromine poisoning
• Xanthene
• Xanthone
• Xanthydrol
• Kidney stone disease

{{Reflist}}

{{Stimulants}}

{{Asthma and copd rx}}

{{Nucleotide metabolism intermediates}}

{{Adenosine receptor modulators}}

{{Chemical classes of psychoactive drugs}}

Category:Enones