Antioxidant activity of aromatic cyclic amine derivatives

Abstract

The antioxidant activities of indolines, indoles, and 1,2,3,4-tetrahydroquinolines in the oxidation of tetralin at 61 °C induced by an azo-initiator were evaluated. Indoline itself and indolines with a methyl or methoxy group were strong antioxidants in this tetralin system. Although indoles and 1,2,3,4-tetrahydroquinolines did not have an antioxidant effect, 5-hydroxyindole and 6-methoxy-1,2,3,4-tetrahydroquinolines were potently antioxidant. Among the antioxidants tested, 5-hydroxyindole exhibited the highest induction period, 1.7 times that of BHT. A semiempirical MNDO-AM1 calculation was applied to study hydrogen abstractions of antioxidants in the chain process of autoxidation. These results indicated that the rates of oxidation during the induction period correlated with the dissociation energies of the N-H bond. © 2002 Elsevier Science Ltd. All rights reserved.