Allantoin was first isolated in 1800 by the Italian physician Michele Francesco Buniva and the French chemist Louis Nicolas Vauquelin, who mistakenly believed it to be present in the amniotic fluid. In 1821, the French chemist Jean Louis Lassaigne found it in the fluid of the allantois; he called it "l'acide allantoique". In 1837, the German chemists Friedrich Wöhler and Justus Liebig synthesized it from uric acid and renamed it "allantoïn".
Animals
Named after the allantois, it is a product of oxidation of uric acid by purinecatabolism. After birth, it is the predominant means by which nitrogenous waste is excreted in the urine of these animals. 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 before excretion. Allantoin has been shown to improve insulin resistance when administered to rats and increased lifespan when administered to the nematode wormCaenorhabditis elegans.
Bacteria
In bacteria, purines and their derivatives are used as secondary sources of nitrogen under nutrient-limiting conditions. Their degradation yields ammonia, which can then be utilized. For instance, Bacillus subtilis is able to utilize allantoin as its sole nitrogen source. Mutants in the B. subtilispucI gene were unable to grow on allantoin, indicating that it encodes an allantoin transporter. In Streptomyces coelicolor, allantoinase and allantoicase are essential for allantoin metabolism. In this species the catabolism of allantoin, and the subsequent release of ammonium, inhibits antibiotic production.
Applications
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.
Cosmetics and toiletries
Manufacturers cite several beneficial effects for allantoin as an active ingredient in over-the-counter cosmetics, including: a moisturizing and keratolytic effect, increasing the water content of the extracellular matrix and enhancing the desquamation of upper layers of dead skin cells, increasing the smoothness of the skin; promoting cell proliferation and wound healing; and a soothing, anti-irritant, and skin protectant effect by forming complexes with irritant and sensitizing agents. An animal study in 2010 found that based on the results from histological analyses, a soft lotion with 5% allantoin ameliorates the wound healing process, by modulating the inflammatory response. The study also suggests that quantitative analysis lends support to the idea that allantoin also promotes fibroblast proliferation and synthesis of the extracellular matrix. A study published in 2009 reported the treatment of pruritus in mild-to-moderate atopic dermatitis with a topical nonsteroidal agent containing allantoin.
Pharmaceuticals
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.
