Spin-Trapping Studies on the Reaction of Iron Complexes with Peroxides and the Effects of Water-Soluble Antioxidants

Abstract

Using ESR spin-trapping techniques we measured the levels of free radical species generated from six different systems (hypoxanthine-xanthine oxidase, iron(II)–hydrogen peroxide, iron(III)–hydrogen peroxide, iron(II)–t-butyl hydroperoxide, iron(III)–t-butyl hydroperoxide, and catalase (CAT)–t-butyl hydroperoxide). Six types of radicals (O₂^−·,·OH, ·H, ·CH₃, (CH₃)₃CO·, and (CH₃)₃COO·) were detected as spin adducts of spin traps 5,5-dimethylpyrroline 1-oxide (DMPO) or 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS). Quantitative analysis of the levels of generated radicals by means of an ESR instrument also presents important information regarding the reduction of peroxides [hydrogen peroxide (H₂O₂) or t-butyl hydroperoxide (ROOH)] by iron(II) or iron(III) as well as catalase. In addition, the scavenging potencies of different water-soluble antioxidants such as L-ascorbic, D-isoascorbic, gallic, sorbic, and protocatechuic acids were evaluated in terms of their ability to reduce the peaks of spin adducts.