No abstract

No abstract

The antioxidant activities of 48 kinds of aminophenols, chromanols, indoles, carbazoles, aromatic amines, and related compounds were assessed in the oxidations of methyl linoleate in acetonitrile solution induced by azo radical initiator. Chromanols, aminochroman and p-phenylenediamines exhibited strong antioxidant activity. Indole and carbazole did not act as antioxidant per se, but those having either amino or hydroxy group as substituent at the para position acted as potent antioxidant. Amino-substituted compounds were in general more potent than hydroxy-substituted ones. These results were interpreted by both polar and resonance effect.

α-Tocopherol and carazostatin (1-heptyl-3-hydroxy-2-methyl-carbazole) acted as a potent antioxidant against lipid peroxidation. α-Tocopherol was more active than carazostatin in homogeneous solution, whereas, in the liposomal membranes, carazostatin exhibited a stronger antioxidant activity than α-tocopherol. This novel finding on such a reversal in relative antioxidant activity by the change in reaction media suggests the importance of mobility of an antioxidant at microenvironment in determining antioxidant activity.

The principal antioxidant in human LDL, a-tocopherol, is converted to the a-tocopheroxyl radical after reaction with peroxyl radicals or Cu 2+, and, if it does not terminate with peroxyl radicals, could initiate lipid peroxidation; a phenomenon called 'tocopherol mediated peroxidation'. Only in the presence of Cn 2+ and low levels of lipid hydroperoxides was an o~-tocopherol dependent decrease in the resistance of LDL to oxidation detected. This suggests that toeopherol mediated peroxidation will probably not contribute significantly as a pro-oxidant process in those individuals most at risk of developing atherosclerosis through an oxidative mechanism.