DL-alpha lipoic acid supplies both Dextro- and Levo-rotary optical enantiomers of lipoic acid, an antioxidant (ORAC scale). See Wikipedia/Chirality_(chemistry) [Links/Chirality].
Alpha-lipoic acid is available in R-lipoic acid and S-lipoic acid forms corresponding to Levorotary and Dextrorotary forms of lipoic acid, so that we should probably speak of DL-lipoic acid as a synonymn for alpha-lipoic acid, typically a 50-50 racemic mixture of both R-(D)-lipoic acid and S-(L)-lipoic acid, although the R-lipoic acid form is twice as prevelant in the blood after administration of 50-50 alpha-lipoic acid as S-lipoic acid. Alpha-lipoic acid is also available in reduced form as a mixture of therapeutically useful R-dihydrolipoic acid and S-dihydrolipoic acid, or pure R-dihydrolipoic acid, which may exhibit stability problems. These also correspond to the Dextrorotary (+) and Levorotary (-) optical enantiomers of the molecule. Kumaran S, Savitha S, Anusuya Devi M, Panneerselvam C. (2004), L-carnitine and DL-alpha-lipoic acid reverse the age-related deficit in glutathione redox state in skeletal muscle and heart tissues, Mech Ageing Dev. 2004 Jul;125(7):507-12. Stevens MJ, Obrosova I, Cao X, Van Huysen C, Greene DA (2000), Effects of DL-alpha-lipoic acid on peripheral nerve conduction, blood flow, energy metabolism, and oxidative stress in experimental diabetic neuropathy, Diabetes 2000 Jun;49(6):1006-15. Palaniyappan Arivazhagan, Kadirvel Ramanathan, Chinnakkannu Panneerselvam (2001), Effect of DL-alpha-lipoic acid on mitochondrial enzymes in aged rats, Chemico-Biological Interactions Volume 138, Issue 2, 28 November 2001, Pages 189-198. P Arivazhagan, S Shila, S Kumaran, C Panneerselvam (2002), Effect of DL-alpha-lipoic acid on the status of lipid peroxidation and antioxidant enzymes in various brain regions of aged rats, Experimental Gerontology Volume 37, Issue 6, 1 June 2002, Pages 803-811.
