ANTIOXIDANT EFFECTS OF THE HYDROXY GROUPS IN THE SIMPLE PHENOLIC CARBAZOLES

Antioxidant activities of the simple phenolic carbazoles 5-11 were evaluated by 2,2-diphenyl-1-picrylhydrazyl and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulfonate) radical scavenging assays. The simple phenolic carbazoles 5-7, 9, and 11 exhibited stronger antioxidant activities than α-tocopherol, and similar antioxidant activities as phenolic carbazole alkaloids carazostatin (1), and carbazomadurins A (3) and B (4). Bond dissociation energies and highest occupied molecule orbital energy levels of a series of phenolic carbazoles including phenolic carbazole alkaloids were calculated. The reducing ability of the phenolic carbazole core could be important role for the antioxidant activity of carbazole alkaloids 1, 3, and 4. Reactive oxygen species (ROS) are highly reactive small substances with an important role in the initiation of various diseases such as carcinogenesis, drug-associated toxicity, inflammation, and atherogenesis as well as aging in aerobic organisms. Natural antioxidants, including ascorbic acid, α-tocopherol (VE), ubiquinol, uric acid, polyphenols and their analogs have been intensive investigation 120 HETEROCYCLES, Vol. 92, No. 1, 2016