Xanthine (/ˈzænθiːn/ or /ˈzænθaɪn/, from Ancient Greekξανθόςxanthós'yellow' 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.[2] Several stimulants are derived from xanthine, including caffeine, theophylline, and theobromine.[3][4]
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.[2]
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.[2][8][9][10][11][12]
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.[13][14] 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.[15][16][17]
^ a b c d e f g h i j k l m n o"Xanthine, CID 1188". PubChem, National Library of Medicine, US National Institutes of Health. 2019. Retrieved 28 September 2019.
^Spiller, Gene A. (1998). Caffeine. Boca Raton: CRC Press. ISBN 0-8493-2647-8.
^ a bKatzung, Bertram G. (1995). Basic & Clinical Pharmacology. East Norwalk, Connecticut: Paramount Publishing. pp. 310, 311. ISBN 0-8385-0619-4.
^Marques LJ, Zheng L, Poulakis N, Guzman J, Costabel U (February 1999). "Pentoxifylline inhibits TNF-alpha production from human alveolar macrophages". Am. J. Respir. Crit. Care Med. 159 (2): 508–11. doi:10.1164/ajrccm.159.2.9804085. PMID 9927365.
^ a bPeters-Golden M, Canetti C, Mancuso P, Coffey MJ (2005). "Leukotrienes: underappreciated mediators of innate immune responses". J. Immunol. 174 (2): 589–94. doi:10.4049/jimmunol.174.2.589. PMID 15634873.
^Daly JW, Jacobson KA, Ukena D (1987). "Adenosine receptors: development of selective agonists and antagonists". Prog Clin Biol Res. 230 (1): 41–63. PMID 3588607.
^Daly JW, Padgett WL, Shamim MT (July 1986). "Analogues of caffeine and theophylline: effect of structural alterations on affinity at adenosine receptors". Journal of Medicinal Chemistry. 29 (7): 1305–8. doi:10.1021/jm00157a035. PMID 3806581.
^Daly JW, Jacobson KA, Ukena D (1987). "Adenosine receptors: development of selective agonists and antagonists". Progress in Clinical and Biological Research. 230: 41–63. PMID 3588607.
^Daly JW, Hide I, Müller CE, Shamim M (1991). "Caffeine analogs: structure-activity relationships at adenosine receptors". Pharmacology. 42 (6): 309–21. doi:10.1159/000138813. PMID 1658821.
^González MP, Terán C, Teijeira M (May 2008). "Search for new antagonist ligands for adenosine receptors from QSAR point of view. How close are we?". Medicinal Research Reviews. 28 (3): 329–71. doi:10.1002/med.20108. PMID 17668454. S2CID 23923058.
^Baraldi PG, Tabrizi MA, Gessi S, Borea PA (January 2008). "Adenosine receptor antagonists: translating medicinal chemistry and pharmacology into clinical utility". Chemical Reviews. 108 (1): 238–63. doi:10.1021/cr0682195. PMID 18181659.
^Martins, Z.; Botta, O.; Fogel, M. L.; Sephton, M. A.; Glavin, D. P.; Watson, J. S.; Dworkin, J. P.; Schwartz, A. W.; Ehrenfreund, P. (2008). "Extraterrestrial nucleobases in the Murchison meteorite". Earth and Planetary Science Letters. 270 (1–2): 130–136. arXiv:0806.2286. Bibcode:2008E&PSL.270..130M. doi:10.1016/j.epsl.2008.03.026. S2CID 14309508.
^AFP Staff (13 June 2008). "We may all be space aliens: study". AFP. Archived from the original on June 17, 2008. Retrieved 2011-08-14.
^Callahan, M. P.; Smith, K. E.; Cleaves, H. J.; Ruzicka, J.; Stern, J. C.; Glavin, D. P.; House, C. H.; Dworkin, J. P. (2011). "Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases". Proceedings of the National Academy of Sciences. 108 (34): 13995–8. Bibcode:2011PNAS..10813995C. doi:10.1073/pnas.1106493108. PMC 3161613. PMID 21836052.
^Steigerwald, John (8 August 2011). "NASA Researchers: DNA Building Blocks Can Be Made in Space". NASA. Retrieved 2011-08-10.
^ScienceDaily Staff (9 August 2011). "DNA Building Blocks Can Be Made in Space, NASA Evidence Suggests". ScienceDaily. Retrieved 2011-08-09.