DETECTION OF FREE-RADICALS IN AQUEOUS EXTRACTS OF CIGARETTE TAR BY ELECTRON-SPIN-RESONANCE

Aqueous extracts of cigarette tar (ACT) autooxidize to produce semiqui none, hydroxyl, and superoxide radicals in air-saturated buffered aque ous solutions. The semiquinone species were detected by direct electro n spin resonance (ESR) measurements and identified as o- and p-benzose miquinone radicals by comparison with the ESR signals of catechol and hydroquinone radicals under similar conditions. The rate of formation of these radicals was dependent on pH. Hydroxyl and superoxide radical s were detected as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin adduct s by ESR spin trapping. Superoxide dismutase (SOD) (20 units/ml) inhib ited the formation of the superoxide spin adduct of DMPO completely. A ddition of Fe2+ to this system increased the ESR signal intensity of h ydroxyl radical spin adduct of DMPO three to five times. These results indicate that superoxide and hydroxyl radicals are produced during th e autooxidation of hydroquinone- and catechol-related species in ACT.