Theoretical investigation of stereochemistry and solvent influence on antioxidant activity of ferulic acid

In this paper, we present a summary of structure – antioxidant activity relation of ferulic acid’s stereoisomers. We have analyzed four antioxidant mechanisms important in free radicals scavenging: hydrogen atom transfer (HAT), sequential proton loss electron transfer (SPLET), single electron transfer – proton transfer (SET-PT) and transition metal chelation (TMC) by calculation of antioxidant descriptors and other related parameters. All calculations have been performed with B3LYP/6-311++G(2d,2p) level of theory in vacuum and in ethanol, water and dimethyl sulfoxide media, based on conductor-like polarizable continuum solvation model. The results have shown that cis-ferulic acid and trans-ferulic acid (including less energetic rotamers) display similar reactivity and, in comparison to previously published results for phenols and polyphenols, may be considered as a good antioxidants. It has been determined that planar structure of ferulic acid (FA) supported by π-electron delocalization positively influences the ability of this compound to neutralize free radicals. Moreover, we have shown that for FA HAT is the most preferable in gas-phase and SPLET is more preferable in all polar media studied. FA might be also considered as a potential transition metals chelating agent.