Allantoin is a chemical compound with formula C4H6N4O3. It is also called 5-ureidohydantoinorglyoxyldiureide.[1][2] It is a diureideofglyoxylic acid. Allantoin is a major metabolic intermediate in most organisms including animals, plants and bacteria. It is produced from uric acid, which itself is a degradation product of nucleic acids, by action of urate oxidase (uricase).[3][4][5] Allantoin also occurs as a natural mineral compound (IMAsymbol Aan[6]).
Allantoin was first isolated in 1800 by the Italian physician Michele Francesco Buniva (1761–1834) and the French chemist Louis Nicolas Vauquelin, who mistakenly believed it to be present in the amniotic fluid.[7] In 1821, the French chemist Jean Louis Lassaigne found it in the fluid of the allantois; he called it "l'acide allantoique".[8] In 1837, the German chemists Friedrich Wöhler and Justus Liebig synthesized it from uric acid and renamed it "allantoïn".[9]
Named after the allantois (anamniote embryonic excretory organ in which it concentrates during development in most mammals except humans and other hominids), it is a product of oxidation of uric acidbypurinecatabolism. After birth, it is the predominant means by which nitrogenous waste is excreted in the urine of these animals.[10] In humans and other higher apes, the metabolic pathway for conversion of uric acid to allantoin is not present, so the former is excreted. Recombinant rasburicase is sometimes used as a drug to catalyze this metabolic conversion in patients. In fish, allantoin is broken down further (into ammonia) before excretion.[11]
Allantoin has been shown to improve insulin resistance when administered to rats and to increase lifespan when administered to the nematode worm Caenorhabditis elegans.[12][13]
In bacteria, purines and their derivatives (such as allantoin) are used as secondary sources of nitrogen under nutrient-limiting conditions. Their degradation yields ammonia, which can then be utilized.[14] For instance, Bacillus subtilis is able to utilize allantoin as its sole nitrogen source.[15]
Mutants in the B. subtilispucI gene were unable to grow on allantoin, indicating that it encodes an allantoin transporter.[16]
InStreptomyces coelicolor, allantoinase (EC 3.5.2.5) and allantoicase (EC 3.5.3.4) are essential for allantoin metabolism. In this species the catabolism of allantoin, and the subsequent release of ammonium, inhibits antibiotic production (Streptomyces species synthesize about half of all known antibiotics of microbial origin).[17]
Allantoin is present in botanical extracts of the comfrey plant and in the urine of most mammals. Chemically synthesized bulk allantoin, which is chemically equivalent to natural allantoin, is safe, non-toxic, compatible with cosmetic raw materials and meets CTFA and JSCI requirements. Over 10,000 patents reference allantoin.[18]
It is frequently present in toothpaste, mouthwash, and other oral hygiene products, in shampoos, lipsticks, anti-acne products, sun care products, and clarifying lotions, various cosmetic lotions and creams, and other cosmetic and pharmaceutical products.[19]
^Pizzichini, Maria; Pandolfi, Maria Luisa; Arezzini, Laura; Terzuoli, Lucia; Fè, Linda; Bontemps, Francois; Van den Berghe, Georges; Marinello, Enrico (1996-08-09). "Labelling of uric acid and allantoin in different purine organs and urine of the rat". Life Sciences. 59 (11): 893–899. doi:10.1016/0024-3205(96)00387-6. PMID8795700.
Liebig and Wöhler (1837) "Ueber die Natur der Harnsäure" (On the nature of uric acid), Annalen der Physik und Chemie, 41 (8) : 561-569. Allantoin is named on p. 563. From p. 563:"Sie sind Allantoïssäure, oder dieselbe Substance, die man in der Allantoïsflussigkeit der Kühe gefunden hat; wir werden sie von nun an Allantoïn nennen." (They [i.e., the crystals previously isolated] are allantois acid, or the same substance that one found in the allantois fluid of cows; we will call it "allantoin" from now on.)
^Kanďár R, Záková P (2008). "Allantoin as a marker of oxidative stress in human erythrocytes". Clinical Chemistry and Laboratory Medicine. 46 (9): 1270–4. doi:10.1515/CCLM.2008.244. PMID18636793. S2CID6420729.
^Zitnanová I, Korytár P, Aruoma OI, Sustrová M, Garaiová I, Muchová J, Kalnovicová T, Pueschel S, Duracková Z (2004). "Uric acid and allantoin levels in Down syndrome: Antioxidant and oxidative stress mechanisms?". Clinica Chimica Acta. 341 (1–2): 139–46. doi:10.1016/j.cccn.2003.11.020. PMID14967170.
