Novel antioxidant reactions of cinnamates in wine

Plant derived polyphenolic compounds have received much attention for their ability to sequester high energy free radicals in a great variety of food related and biological systems, protecting those systems from oxidative change. The ability of these compounds to scavenge free radicals has always been attributed to their phenolic functionality, from which a hydrogen atom can be easily abstracted. In this study, the cinnamates and the ubiquitous hydroxycinnamates, were found to equally suppress the formation of oxidation products (acetaldehyde) in wine exposed to the Fenton reaction (catalytic Fe(II) and hydrogen peroxide). Mechanistic investigations led to the unexpected discovery that the alpha,beta--unsaturated sidechains of caffeic, coumaric, ferulic, and even cinnamic acids, trap 1-hydroxylethyl radicals representing a newly discovered mode of antioxidant, radical scavenging activity for these broadly occurring compounds in a food system. The pathway was established by identifying the product of reaction between the cinnamates and the ethoxyl radical. The proposed pathway is supported by prior fundamental studies with radiolytically-generated radicals.