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Alpha-lipoic acid

Lipoic acid is an essential nutrient and coenzyme which functions with close similarity to thiamine in the initial decarboxylation step of pyruvate. Lipoic acid has two sulfur bonds that combine with thiamine to form thiamine pyrophosphate [TPP] to participate in a key reaction of oxidative decarboxylation to reduce pyruvate to active acetate, thereby allowing for forming of acetyl coenzyme A and its entry into the Krebs cycle, the final energy cycle. Alpha-Lipoic acid is known as thioctic acid, 1,2-dithiolane-3-pentanoic acid, 1,2-dithiolane-3-valeric acid and 6,8-thioctic acid. Alpha-lipoic acid is distributed widely in plants and animals in the form of the R-enantiomer; it acts as a coenzyme in many enzymatic reactions, constitutes a growth factor for certain bacteria and protozoa and is used to treat death-head mushroom poisoning. The alpha-lipoic acid racemate also has anti-inflammatory, antinociceptive (analgesic) and cytoprotective, neuroprotective, anti-allergic and antitumor properties. Alpha-lipoic acid, in addition to its non-toxicity and lipophilicity, has the advantage of being rapidly converted in tissues into its reduced form, dihydrolipoic acid (DHLA). DHLA reacts with reactive oxygen species such as superoxide radicals, hydroxyl radicals, hypochlorous acid, peroxyl radicals, and singlet oxygen. It also protects membranes by interacting with vitamin C and glutathione, which may in turn recycle vitamin E. In addition to its antioxidant activities, DHLA may exert prooxidant actions to reduction of iron. DHLA also has potent antioxidant effects. Both alpha-lipoic acid and DHLA can disarm oxidants through a variety of mechanisms including free radical quenching, metal chelation, and regeneration of other common natural antioxidants. Alpha-lipoic acid and the DHLA redox together are excellent antioxidants capable of interacting with most forms of reactive oxygen species, recycling other antioxidants and additionally reducing oxidized disulfide groups in biological systems. These molecules then may recuperate their biological reducing power and function. Alpha-lipoic acid is pharmacologically active and possesses, among other features, antiphlogistic and antinociceptive as well as cytoprotective properties. Alpha-lipoic acid administration has been shown to be beneficial in a number of oxidative stress models such as ischemia-reperfussion injury (IRI), diabetes, cataract formation, HIV activation, neurodegeneration, and radiation injury. Another important medical indication is the treatment of diabetic polyneuropathy.

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