Lipoic acid

Lipoic acid (LA), also known as α-lipoic acid and alpha lipoic acid (ALA) and thioctic acid is an organosulfur compound derived from caprylic acid (octanoic acid). ALA is made in animals normally, and is essential for aerobic metabolism. It is also manufactured and is available as a dietary supplement in some countries where it is marketed as an antioxidant, and is available as a pharmaceutical drug in other countries.Lipoic acid (LA), also known as α-lipoic acid, alpha lipoic acid (ALA) and thioctic acid is an organosulfur compound derived from octanoic acid. LA contains two sulfur atoms (at C6 and C8) connected by a disulfide bond and is thus considered to be oxidized although either sulfur atom can exist in higher oxidation states.'Lipoate' is the conjugate base of lipoic acid, and the most prevalent form of LA under physiologic conditions. Most endogenously produced RLA are not 'free' because octanoic acid, the precursor to RLA, is bound to the enzyme complexes prior to enzymatic insertion of the sulfur atoms. As a cofactor, RLA is covalently attached by an amide bond to a terminal lysine residue of the enzyme's lipoyl domains. One of the most studied roles of RLA is as a cofactor of the pyruvate dehydrogenase complex (PDC or PDHC), though it is a cofactor in other enzymatic systems as well (described below).SLA did not exist prior to chemical synthesis in 1952. SLA is produced in equal amounts with RLA during achiral manufacturing processes. The racemic form was more widely used clinically in Europe and Japan in the 1950s to 1960s despite the early recognition that the various forms of LA are not bioequivalent. The first synthetic procedures appeared for RLA and SLA in the mid-1950s. Advances in chiral chemistry led to more efficient technologies for manufacturing the single enantiomers by both classical resolution and asymmetric synthesis and the demand for RLA also grew at this time. In the 21st century, R/S-LA, RLA and SLA with high chemical and/or optical purities are available in industrial quantities. At the current time, most of the world supply of R/S-LA and RLA is manufactured in China and smaller amounts in Italy, Germany, and Japan. RLA is produced by modifications of a process first described by Georg Lang in a Ph.D. thesis and later patented by DeGussa. Although RLA is favored nutritionally due to its “vitamin-like” role in metabolism, both RLA and R/S-LA are widely available as dietary supplements. Both stereospecific and non-stereospecific reactions are known to occur in vivo and contribute to the mechanisms of action, but evidence to date indicates RLA may be the eutomer (the nutritionally and therapeutically preferred form).A 2007 human pharmacokinetic study of sodium RLA demonstrated the maximum concentration in plasma and bioavailability are significantly greater than the free acid form, and rivals plasma levels achieved by intravenous administration of the free acid form. Additionally, high plasma levels comparable to those in animal models where Nrf2 was activated were achieved.R/S-LA and RLA are widely available as over-the-counter nutritional supplements in the United States in the form of capsules, tablets, and aqueous liquids, and have been marketed as antioxidants. In 2008 evidence had accumulated that questioned whether these compounds functioned through a direct antioxidant effect in the body, or rather through an indirect method like inducing synthesis of endogenous antioxidants like glutathione.According to the American Cancer Society as of 2013, 'there is no reliable scientific evidence at this time that lipoic acid prevents the development or spread of cancer'. As of 2015, intravenously administered ALA is unapproved anywhere in the world except Germany for diabetic neuropathy, but has been proven reasonably safe and effective in four clinical trials; however another large trial over four years found no difference from placebo. As of 2012, there was no good evidence alpha lipoic acid helps people with mitochondrial disorders.