Electron spin resonance as a powerful tool for studying antioxidants and radicals.

The study of antioxidants and radicals has always been a complex task due to the special characteristics of these species such as reactions at low concentrations and short half-lives. Current techniques do not always produce good results and in some cases they can only be applied in chemical models. From this point of view, the development of electron spin resonance (ESR) has allowed the study of the antioxidant capacity of a wide variety of compounds and the detection of radicals in the reactions in which they are involved. The DPPH technique allows only the study of antioxidants in pure chemical models. The ORAC-ESR assay, based on the spin trapping technique, emerges as an interesting tool for identifying and quantifying the antioxidant capacity of different samples. Furthermore, the spin trapping technique allows us to characterize radicals in in vivo/ex vivo models. The present review discusses the current available techniques associated with ESR for the study of antioxidants and radical species.