Alpha-lipoic acid (ALA)

Alpha-lipoic acid (ALA), also known as lipoic acid or thioctic acid, is a naturally occurring organosulfur compound synthesized by plants and animals, including humans. It functions primarily as an essential cofactor for multiple mitochondrial enzyme complexes responsible for critical reactions in energy and amino acid metabolism; specifically, it is covalently bound as a prosthetic group to enzyme complexes such as pyruvate dehydrogenase and the glycine cleavage system. ALA acts as a potent antioxidant and can exist in both oxidized (ALA) and reduced (dihydrolipoic acid, DHLA) forms. Only the R-enantiomer occurs naturally and is biologically functional; supplements are available as either R-ALA or a racemic mixture. While ALA is widely marketed as a nutraceutical and is investigated for potential therapeutic effects in neuropathy, diabetes, and neurodegenerative diseases, it is not a receptor, enzyme, ion channel, transporter, or classical therapeutic target, but rather a small molecule enzyme cofactor and antioxidant.

Other names

Lipoic acidThioctic acidα-lipoic acidR-lipoic acid(R)-(+)-lipoic acid(R)-1,2-dithiolane-3-pentanoic acidDL-thioctic acidAlpha acid lipoicD-thioctic acid6,8-thioctic acidLipoateBiletanDL-6,8-thioctic acid

Antioxidant activity (direct free radical scavenging, regeneration of other antioxidants), enzyme cofactor for mitochondrial α-ketoacid dehydrogenase complexes (energy metabolism)