Lipoic acid, also known as α-lipoic acid, alpha lipoic acid (ALA) and thioctic acid is an organosulfur compound derived from octanoic acid. Lipoic acid is a cofactor for at least five enzyme systems. Two of these are in the citric acid cycle through which many organisms turn nutrients into energy.
Lipoic acid is present in almost all foods, but slightly more so in kidney, heart, liver, spinach, broccoli, and yeast extract. Naturally occurring lipoic acid is always covalently bound and not readily available from dietary sources.