| Summary: | Lipid hydroperoxides play an important role in various pathophysiological processes. Therefore, a simple model for organic hydroperoxides could be helpful to monitor the biologic effects of endogenous and exogenous compounds. The electron paramagnetic resonance (EPR) spin-trapping technique is a useful method to study superoxide (O<sub>2</sub><sup>•−</sup>) and hydroxyl radicals. The aim of our work was to use EPR with the spin trap 5-<i>tert</i>-butoxycarbonyl-5-methyl-1-pyrroline-<i>N</i>-oxide (BMPO), which, by trapping O<sub>2</sub><sup>•−</sup> produces relatively stable <sup>•</sup>BMPO-OOH spin-adduct, a valuable model for organic hydroperoxides. We used this experimental setup to investigate the effects of selected sulfur/selenium compounds on <sup>•</sup>BMPO-OOH and to evaluate the antioxidant potential of these compounds. Second, using the simulation of time-dependent individual BMPO adducts in the experimental EPR spectra, the ratio of <sup>•</sup>BMPO-OH/<sup>•</sup>BMPO-OOH—which is proportional to the transformation/decomposition of <sup>•</sup>BMPO-OOH—was evaluated. The order of potency of the studied compounds to alter <sup>•</sup>BMPO-OOH concentration estimated from the time-dependent <sup>•</sup>BMPO-OH/<sup>•</sup>BMPO-OOH ratio was as follows: Na<sub>2</sub>S<sub>4</sub> > Na<sub>2</sub>S<sub>4</sub>/SeO<sub>3</sub><sup>2−</sup> > H<sub>2</sub>S/SeO<sub>3</sub><sup>2−</sup> > Na<sub>2</sub>S<sub>2</sub> ~Na<sub>2</sub>S<sub>2</sub>/SeO<sub>3</sub><sup>2−</sup> ~H<sub>2</sub>S > SeO<sub>3</sub><sup>2−</sup> ~SeO<sub>4</sub><sup>2−</sup> ~control. In conclusion, the presented approach of the EPR measurement of the time-dependent ratio of <sup>•</sup>BMPO-OH/<sup>•</sup>BMPO-OOH could be useful to study the impact of compounds to influence the transformation of <sup>•</sup>BMPO-OOH.
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