Evaluation of various spin traps for the in vivo in situ detection of hydroxyl radical

Abstract

The ideal spin trap for the in vivo in situ detection of HO˙ is one that reacts specifically with this free radical at near diffusion controlled rates. Further, the corresponding spin trapped adducts must be sufficiently long-lived to allow the acquisition of EPR spectra for prolonged periods of time. Herein, we report on our studies in which we explored the ability of various imidazole N-oxides, an isoquinoline N-oxide and pyrroline N-oxides to specifically react with HO˙ at the expense of O₂^˙–. Further, we estimated the rate constant for spin trapping HO˙. Finally, we measured the stability of the corresponding spin trapped adducts. Our data suggest that imidazole N-oxides, in particular 2,2-dimethyl-4-methoxycarbonyl-2H-imidazole 1-oxide (3), appear to be the best spin traps for the in vivo in situ detection of HO˙ in real time.