Alphahydroxycarboxylic

Alpha-hydroxycarboxylic acids, also known as alpha-hydroxy acids or 2-hydroxy carboxylic acids, are a class of organic compounds that contain a carboxyl group adjacent to a hydroxyl-bearing carbon. Their simplest member is glycolic acid (hydroxyacetic acid); other common examples include lactic acid (2-hydroxypropionic acid), mandelic acid (2-hydroxyphenylacetic acid), and malic acid (2-hydroxybutanedioic acid). Many AHAs occur naturally in fruits and plant-derived products and are used in various chemical and pharmaceutical contexts.

AHAs are typically small, highly polar molecules that dissolve readily in water. The presence of the alpha-hydroxyl group enhances reactivity and hydrogen-bonding capacity compared to simple carboxylic acids. They can exist as different ionic forms depending on pH, and some AHAs are chiral, yielding enantiomerically enriched derivatives. Their acidity (carboxyl pKa values) generally falls in the acidic range, often influenced by substituents on the alpha carbon.

Industrial and cosmetic use is broad. In cosmetics, glycolic and lactic acids are popular chemical exfoliants, promoting desquamation and increased cell turnover in the skin. Mandelic and malic acids are also used for exfoliation, offering varying penetration and irritation profiles. In foods and fermentation products, AHAs like malic acid act as flavor enhancers and acidity regulators. They also serve as intermediates in organic synthesis.

Safety and regulation emphasize cautious use: AHAs can irritate the skin and increase sensitivity to sunlight, especially at higher concentrations. Products typically include usage guidelines and sunscreen recommendations. See also glycolic acid, lactic acid, and alpha-hydroxy acids in cosmetic and pharmaceutical contexts.