SPIN-TRAPPING STUDIES ON THE REACTION OF IRON COMPLEXES WITH PEROXIDES AND THE EFFECTS OF WATER-SOLUBLE ANTIOXIDANTS

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.