Assessment of Oxidative Balance in the Lipo- and Hydro-philic Cellular Environment in Biological Systems

Abstract

Over the last decade, Electron Paramagnetic Resonance (EPR) technology has been successfully applied to detect free radicals in order to establish oxidative stress conditions. Since a variety of stable products are formed during the oxidation of lipids, several assays have been developed over the years in order to evaluate lipid peroxidation. EPR spectroscopy has shown the capacity to detect, in the presence of exogenous traps, the presence of lipid radicals (LR•) formed during peroxidation, by yielding unique and stable compounds. On the other hand, the one-electron oxidation of AH- produces ascorbyl radical (A•) which is easily detectable by EPR, even at room-temperature in aqueous solution. The A• free radical has a relatively long lifetime compared to other species, such as hydroxyl radical, peroxyl, alkoxyl, and LR• and has been proposed as a marker of oxidative stress, either in vitro or in vivo, in numerous systems, such as plasma. All biological systems contain many antioxidants, including both water-soluble compounds (such as AH- and glutathione), and lipid-soluble antioxidants, such as - tocopherol (-T). In this chapter, the most widely used indexes of oxidative balance in biological systems will be briefly summarized. Moreover, special mention will be made about the application of the A•/AH- and LR•/-T ratios to situations of oxidative stress. The goal of this work is to discuss the possibility of detecting the actual state of lipid- and water-soluble fractions of a biological system, providing an early and simple diagnosis of stressing conditions.