Lipoic acid is an endogenous antioxidant, which can remove the body's free radicals, promote the body's synthesis of vitamin C using glucose, and promote the synthesis of glutathione, effectively remove melanin, and assist coenzyme in physiological metabolism conducive to the body's immunity. Lipoic acid also has anti-inflammatory effect, can inhibit the activities of kinase, transforming factor, tumor necrosis factor and collagenase, and has anti-aging effect. Lipoic acid can preserve and regenerate other antioxidants and has a good health function to human body. It is widely used in the prevention and treatment of heart disease, diabetes, liver disease and Alzheimer's disease. The two enantiomers of lipoic acid showed different biological activities. Among them, R-type enantiomers are more effective than S-type enantiomers, which may be due to the fact that a large amount of R-type lipoic acid can enter cells and mitochondria through cell membrane and mitochondrial membrane and be reduced to dihydrolipoic acid, while only a small amount of S-type can enter cells and be reduced. Dihydrolipoic acid has stronger antioxidant capacity than lipoic acid. The regeneration of endogenous antioxidants and the repair of oxidative damage can only be achieved by dihydrolipoic acid.