Chapter 7 - Different theoretical approaches in the study of antioxidative mechanisms

Abstract

Antioxidants can reveal their activity through several different but similar reaction mechanisms such as hydrogen atom transfer (HAT), proton-coupled electron transfer (PCET), single-electron transfer (SET), single-electron transfer followed by proton transfer (SET-PT), sequential proton loss electron transfer (SPLET), sequential proton loss hydrogen atom transfer (SPLHAT), and radical adduct formation (RAF). The antioxidative properties of natural phenolic compounds (quercetin, gallic acid, and dihydroxybenzoic acids) were examined applying the density functional theory (DFT). The potency of free radical scavenging of the mentioned compounds was analyzed using the thermodynamic parameters: bond dissociation enthalpy, ionization potential, proton dissociation enthalpy, proton affinity, and electron-transfer enthalpy. The influence of different radicals was estimated on the bases of reactions enthalpies between antioxidants and free radical species. The effect of free radicals on HAT, PCET, and SPLET mechanisms is explained by means of a mechanistic approach. The obtained results contribute to the elucidation and understanding of the complex processes involved in the antioxidative action.