Study of the mechanisms of antioxidative action of different antioxidants

The reaction mechanisms by which antioxidants can exert their activity are: hydrogen atom transfer (HAT), proton coupled electron transfer (PCET), sequential proton loss electron transfer (SPLET), single electron transfer proton transfer (SET-PT), radical adduct formation, and sequential proton loss hydrogen atom transfer. The antioxidative activity of different compounds (flavones, flavonols, and Schiff basis) was investigated by the trolox equivalent antioxidative capacity and electron paramagnetic resonance methods. The mechanisms of the antioxidative action (HAT, PCET, SPLET, and SET-PT) were investigated by using the thermodynamic parameters: bond dissociation enthalpy, ionization potential, proton dissociation enthalpy, proton affinity, and electron-transfer enthalpy. The influence of different radicals was investigated using appropriate isodesmic reactions. The mechanistic approach to the investigation of the influence of different radicals to the HAT mechanism, and the second step of the SET-PT mechanism) was applied. These investigations contribute to the elucidation and understanding of complex processes involved in the antioxidative action.