Physico‐chemical principles of antioxidant action, including solvent and matrix dependence and interfacial phenomena

This chapter describes a few very general concepts (mechanisms and methodology of measurements) necessary to understand how the microenvironment and interfacial water/lipid phenomena can affect the behavior of antioxidants. It then describes several problems, including the role of a charge of the initiating radicals, the polarity of propagating radicals, polarity of chain‐breaking antioxidant (CBA), pH, the role of hydrogen bonding, and the synergy of lipid‐soluble CBA with water‐soluble co‐antioxidants. Based on the described considerations, one can conclude that the most reliable methods of determination of antioxidant activity are based on the kinetic and mechanistic studies of antioxidant behavior during peroxidation of lipids, polymers, and other biomolecules, that is, in the systems where reaction 12.14 is directly responsible for breaking the propagation chain of peroxidation. These methods involve the measurements of autoxidation rate by oxygen uptake, or by detection of primary or secondary products of autoxidation.