Proton-Coupled Electron Transfer and Hydrogen Tunneling in Olive Oil Phenol Reactions
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Published:2024-06-07
Issue:12
Volume:25
Page:6341
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ISSN:1422-0067
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Container-title:International Journal of Molecular Sciences
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language:en
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Short-container-title:IJMS
Author:
Torić Jelena1, Karković Marković Ana1ORCID, Mustać Stipe1, Pulitika Anamarija2ORCID, Jakobušić Brala Cvijeta1ORCID, Pilepić Viktor1ORCID
Affiliation:
1. Faculty of Pharmacy and Biochemistry, University of Zagreb, 10000 Zagreb, Croatia 2. Faculty of Chemical Engineering and Technology, University of Zagreb, 10000 Zagreb, Croatia
Abstract
Olive oil phenols are recognized as molecules with numerous positive health effects, many of which rely on their antioxidative activity, i.e., the ability to transfer hydrogen to radicals. Proton-coupled electron transfer reactions and hydrogen tunneling are ubiquitous in biological systems. Reactions of olive oil phenols, hydroxytyrosol, tyrosol, oleuropein, oleacein, oleocanthal, homovanillyl alcohol, vanillin, and a few phenolic acids with a DPPH• (2,2-diphenyl-1-picrylhydrazyl) radical in a 1,4-dioxane:water = 95:5 or 99:1 v/v solvent mixture were studied through an experimental kinetic analysis and computational chemistry calculations. The highest rate constants corresponding to the highest antioxidative activity are obtained for the ortho-diphenols hydroxytyrosol, oleuropein, and oleacein. The experimentally determined kinetic isotope effects (KIEs) for hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions are 16.0, 15.4, and 16.7, respectively. Based on these KIEs, thermodynamic activation parameters, and an intrinsic bond orbital (IBO) analysis along the IRC path calculations, we propose a proton-coupled electron transfer mechanism. The average local ionization energy and electron donor Fukui function obtained for the phenolic compounds show that the most reactive electron-donating sites are associated with π electrons above and below the aromatic ring, in support of the IBO analysis and proposed PCET reaction mechanism. Large KIEs and isotopic values of Arrhenius pre-exponential factor AH/AD determined for the hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions of 0.6, 1.3, and 0.3, respectively, reveal the involvement of hydrogen tunneling in the process.
Funder
FarmInova European Regional Development Fund
Reference84 articles.
1. Free Radicals, Reactive Oxygen Species, Oxidative Stress and Its Classification;Lushchak;Chem.-Biol. Interact.,2014 2. Reactive Oxygen Species, Toxicity, Oxidative Stress, and Antioxidants: Chronic Diseases and Aging;Jomova;Arch. Toxicol.,2023 3. Finicelli, M., Di Salle, A., Galderisi, U., and Peluso, G. (2022). The Mediterranean Diet: An Update of the Clinical Trials. Nutrients, 14. 4. Bucciantini, M., Leri, M., Nardiello, P., Casamenti, F., and Stefani, M. (2021). Olive Polyphenols: Antioxidant and Anti-Inflammatory Properties. Antioxidants, 10. 5. Gorzynik-Debicka, M., Przychodzen, P., Cappello, F., Kuban-Jankowska, A., Marino Gammazza, A., Knap, N., Wozniak, M., and Gorska-Ponikowska, M. (2018). Potential Health Benefits of Olive Oil and Plant Polyphenols. Int. J. Mol. Sci., 19.
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