33] Overview of methods used for detecting lipid peroxidation

Abstract

Lipid peroxidation is a complex process whereby unsaturated lipid material undergoes reaction with molecular oxygen to yield lipid hydroperoxides; in most situations involving biological samples, the lipid hydroperoxides are degraded to a variety of products, including aikanals, alkenals, hydroxyalkenals, ketones, and alkanes. Although attack by singlet oxygen on unsaturated lipid has been shown to give lipid hydroperoxide by a nonradical, nonchain process, the vast majority of situations involving lipid peroxidation proceed through a free radical-mediated chain reaction initiated by the abstraction of a hydrogen atom from the unsaturated lipid by a reactive free radical, followed by a complex sequence of propagative reactions. The peroxidation of polyunsaturated fatty acids (PUFAs) can proceed through nonenzymic autoxidative pathways or through processes that are enzymically catalyzed. The importance of autoxidation in the deterioration of foods, and in the oil industry, has long been recognized, and authoritative reviews are available for such aspects. A relatively new growth point for studies on lipid peroxidation has been the realization that many toxic agents can be metabolically activated within cells to free-radical intermediates that can initiate lipid peroxidation and result in cell injury. A very large number of such studies on lipid peroxidation in biological systems have demonstrated the degradation of membrane PUFAs, with a subsequent disorganization of membrane structure and disturbance of membrane function. This chapter discusses the methods used for studying lipid peroxidation concentrates on such aspects of lipid peroxidation in relation to biomembrane disturbance.