THE LIPOIC ACID ANALOG 1,2-DISELENOLANE-3-PENTANOIC ACID PROTECTS HUMAN LOW-DENSITY-LIPOPROTEIN AGAINST OXIDATIVE MODIFICATION MEDIATED BY COPPER-ION

1,2-Diselenolane-3-pentanoic acid, in which the sulfur atoms of alpha- lipoic acid are replaced with selenium, displayed markedly different a ntioxidant properties when compared to alpha-lipoic acid. 1,2-Diseleno lane-3-pentanoic acid was unable to inhibit protein oxidative modifica tion of human low density lipoprotein (LDL) and bovine serum albumin i nduced by copper ion or hydroxyl radical, whereas alpha-lipoic acid sh owed significant protection. However, 1,2-diselenolane-3-pentanoic aci d was able to inhibit the formation of lipid peroxidation products in LDL after oxidation by copper, while alpha-lipoic acid did not. Hence the diselenium compound exerts its effects in a lipophilic environment whilst lipoic acid exerts its effects in a hydrophilic environment. T hese differences in antioxidant activities of the two compounds may be explained, at least in part, by their differing partition coefficient s. (C) 1997 Academic Press.