Lipoic Acid: Cellular Metabolism, Antioxidant Activity, and Clinical Relevance

I. INTRODUCTION R-α-Lipoic acid (R-LA) is a naturally occurring compound present as a cofactor in several mitochondrial enzymes that are involved in metabolism and energy production. α-Lipoic acid (LA) was first isolated in 1951 by Reed and colleagues (1). It is an eight-carbon compound containing two sulfur atoms in a dithiolane ring structure. The two enantiomers of LA are the S form and the R form (Fig. 1). In its free form, LA is a powerful antioxidant, functioning as a reactive oxygen species scavenger.