The role of phenolics, conjugated linoleic acid, carnosine, and pyrroloquinoline quinone as nonessential dietary antioxidants.

Oxidative reactions have been implicated in the development of numerous diseases including atherosclerosis and cancer. Oxidation of lipids, proteins, and nucleic acids can result in loss of membrane integrity and function, inactivation of enzymes, modification of lipoproteins, and chemical alteration of DNA. Active oxygen species, transition metals, reducing agents, and enzymes such as lipoxygenase are all involved in the catalysis of oxidative reactions. Since lipid oxidation catalysts and active oxygen species are ubiquitous to all biological systems and since lipid oxidation products can enter the body via oxidized foods, numerous endogenous antioxidant systems have been developed. Endogenous antioxidant systems include antioxidant enzymes, free radical scavengers, and metal chelators. The purpose of this review is to examine the potential of nonessential dietary components that inhibit oxidative reactions in foods and biological tissues.