QUANTITATIVE ELECTRON-SPIN-RESONANCE (ESR) ANALYSIS OF ANTIOXIDATIVE PROPERTIES USING THE ACETALDEHYDE XANTHINE-OXIDASE SYSTEM

present a method for the quantitative ESR analysis of the antioxidant properties of drugs using the acetaldhehyde/xanthine oxidase (AC/XOD) superoxide generating system and 5,5-dimethyl-1-pyrroline-N-oxide (DMP O) as spin trap. In stoichiometric conditions (AC/XOD, 60 mM / 0.018 U ), the resulting paramagnetic DMPO adduct disappeared with superoxide dismutase and remained when catalase or DMSO were used. That adduct wa s dependent only on superoxide and resulted from the trapping of a car boxyl radical by DMPO (a(N) = 15.2 G, a(H) = 18.9 G). Similar results were obtained using 4-pyridyl-1-oxide-N-t-butyl nitrone (POBN) as spin trap. The ESR signal of the DMPO-CO2- adduct was very stable and allo wed quantitative analysis of the antioxidative activity of redox molec ules from an IC50 value representing the concentration causing 50% inh ibition of its intensity. Among the tested compounds, manganese(II) co mplexes were the most effective, 25 times as active as ascorbic acid o r (+)catechin and 500-fold more antioxidative than Trolox(R).