Interrelationships of Lipoic Acids

The Chemistry and Function of Lipoic Acid

“…Reed et al (83,84) concluded independently that p-lipoic acid was a sulfoxide of a-lipoic acid. The partial conversion of a-lipoic acid to 8-lipoic acid in the preparation of paper chromatograms, suggesting that the latter substance was an oxidation product of a-lipoic acid, was mentioned previously.…”

“…In 1951 Reed et al (82) reported the isolation of a crystalline organic acid, which was highly active in the acetate-replacing factor and pyruvate oxidation factor assays, and proposed the name ('alipoic acid" to designate this substance. Subsequently, Patterson et al (69) reported the isolation of a crystalline derivative of one of the forms of protogen, and designated this form '( protogen-B" (8-lipoic acid)).…”

Enzymic Mechanisms in the Citric Acid Cycle

“…This compound has been named a-lipoic (200) or thioctic (19) acid. A derivative of protogen B, isolated by the group at Lederle Laboratories (179), is a sulfoxide which corresponds to the &lipoic acid of Reed et al (201). The aulfoxide appears to be a chemical oxidation product of the cyclic disulfide and not to function in biological systems.…”

Determination of free α-lipoic acid in foodstuffs by HPLC coupled with CEAD and ESI-MS

“…In biological systems, a-LA can occur either in a free form, associated to proteins by hydrogen bonds or in a protein-bound form via amide linkage between the e-amino group of a lysine residue and the carboxylic group of a-LA (Bradford, Howell, Aitken, James, & Yeaman, 1987;Reed, Koike, Levitch, & Leach, 1958), but it also forms mixed disulphides [Reed, DeBusk, Hornberger, & Gunsalus, 1953) and disulphide polymers (Thomas & Reed, 1956). The antioxidative activity of free a-LA has been studied in detail, but the antioxidant activity of the protein-bound lipoic acid has hardly been elucidated (Matsugo, Yasui, & Ozaki, 2003).…”