Undecylenic acid is an organic compound unsaturated with the formula CH2=CH(CH2)8CO2H. It is an unsaturated fatty acid and forms a colorless oil at room temperature and pressure. Undecylenic acid is mainly used for the production of Nylon-11 and in the treatment of fungal infections of the skin, but it is also a precursor in the manufacture of many pharmaceuticals, personal hygiene products, cosmetics, and perfumes. Salts and esters of undecylenic acid are known as undecylenates.
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Preparation
Undecylenic acid is prepared by pyrolysis of ricinoleic acid, which is derived from castor oil. Specifically, the methyl ester of ricinoleic acid is subjected to the chemical process of cracking to yield both undecylenic acid and heptanal. The process is conducted at 500–600 °C in the presence of steam. The methyl ester is then hydrolyzed.
General commercial uses
Undecylenic acid is converted to 11-aminoundecanoic acid on an industrial scale. This aminocarboxylic acid is the precursor to Nylon-11. Undecylenic acid is reduced via its acid chloride to the aldehyde undecylene aldehyde, which is valued in perfumery. Undecylenic acid is also a precursor to antidandruff shampoos and antimicrobial powders.
Medical uses
Undecylenic acid is an active ingredient in medications for skin infections, and to relieve itching, burning, and irritation associated with skin problems. For example, it is used against fungal skin infections, such as athlete's foot, ringworm, tinea cruris, or other generalized infections by Candida albicans. When used for tinea cruris, it can result in extreme burning. In some case studies of tinae versicolor, pain and burning result from fungicide application.
In a review of placebo-controlled trials, undecenoic acid was deemed efficacious, alongside prescription azoles (e.g., clotrimazole) and allylamines (e.g., terbinafine), though there were not "sufficient comparative trials to judge relative efficacy."
One of mechanisms underlying its antifungal effects against Candida albicans is its inhibition of morphogenesis. In a study on denture liners, undecylenic acid in the liners was found to inhibit conversion of yeast to the hyphal form (which are associated with active infection), via inhibition of fatty acid biosynthesis. The mechanism of action and effectiveness in fatty acid-type antifungals is dependent on the number of carbon atoms in the chain, with efficacy increasing with the number of atoms in the chain.
FDA approval
Undecylenic acid is approved by the U.S. FDA for topical route and is listed in the Inactive Ingredient Database.
Research uses
Undecylenic acid has been used as a linking molecule, because it is a bifunctional compound, in this case, an α,ω- (terminally functionalized) bifunctional agent. For instance, the title compound has been used to prepare silicon-based biosensors, linking silicon transducer surfaces to the terminal double bond of undecylenic acid (forming an Si-C bond), leaving the carboxylic acid groups available for conjugation of biomolecules (e.g., proteins).