Antioxidant activity of caffeic acid: thermodynamic and kinetic aspects on the oxidative degradation pathway

Abstract

Caffeic acid is a phenolic secondary metabolite from plants, which is known for its antioxidant properties. The effective mitigation of methanol-induced oxidative stress by caffeic acid depends on the direct radical scavenging as well as the formation of new metabolites via oxidative degradation. Herein, thermodynamic and kinetic aspects of the oxidative degradation pathway of caffeic acid in the presence of radical CH₃O^• and its isomer, ^•CH₂OH are discussed for the first time, employing density functional theory (DFT). The direct radical scavenging activity of caffeic acid against these radicals is verified via hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms. HAT is predicted to be more feasible than RAF mechanism as per the computed data. Additionally, energetic details of the proposed oxidative degradation pathway of radical adduct intermediates toward the formation of a cyclic metabolite is analyzed. Kinetic studies indicated a significant tunneling contribution to the H abstraction pathways having high activation barriers. Further, our results imply that the newly formed metabolites exhibit comparable antioxidant activity with that of caffeic acid.

Keywords:

• Caffeic acid
• density functional theory
• hydrogen atom transfer
• radical adduct formation
• oxidative degradation

Acknowledgements

We thank Department of Chemistry, Central University of Kerala for providing computational facilities. AP is grateful to Kerala State Council for Science, Technology and Environment (KSCSTE) for the award of Senior Research Fellowship.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

AP is grateful to Kerala State Council for Science, Technology and Environment (KSCSTE) for the award of Senior Research Fellowship.