Free Radical Scavenging by Natural Polyphenols: Atom versus Electron Transfer

Polyphenols (synthetically modified or directly provided by human diet) scavenge free radicals by H-atom transfer and may thus decrease noxious effects due to oxidative stress. Free radical scavenging by polyphenols has been widely theoretically studied from the thermodynamic point of view whereas t...

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Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2013-03, Vol.117 (10), p.2082-2092
Main Authors: Di Meo, Florent, Lemaur, Vincent, Cornil, Jérôme, Lazzaroni, Roberto, Duroux, Jean-Luc, Olivier, Yoann, Trouillas, Patrick
Format: Article
Language:English
Subjects:
Catechols - chemistry
Chemical Sciences
Chemistry
Computational efficiency
Computing time
Electron transfer
Electron Transport
Electrons
Exact sciences and technology
Free Radical Scavengers - chemistry
Free radicals
Free Radicals - antagonists & inhibitors
Hydrogen-Ion Concentration
Kinetics
Mathematical analysis
Molecular Structure
or physical chemistry
Organic chemistry
Polyphenols
Polyphenols - chemistry
Quantum Theory
Quercetin - chemistry
Reactivity and mechanisms
Scavengers
Scavenging
Solutions
Structure-Activity Relationship
Theoretical and
Thermodynamics
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Summary:Polyphenols (synthetically modified or directly provided by human diet) scavenge free radicals by H-atom transfer and may thus decrease noxious effects due to oxidative stress. Free radical scavenging by polyphenols has been widely theoretically studied from the thermodynamic point of view whereas the kinetic point of view has been much less addressed. The present study describes kinetic-based structure–activity relationship for quercetin. This compound is very characteristic of the wide flavonoid subclass of polyphenols. H-atom transfer is a mechanism based on either atom or electron transfer. This is analyzed here by quantum chemical calculations, which support the knowledge acquired from experimental studies. The competition between the different processes is discussed in terms of the nature of the prereaction complexes, the pH, the formation of activated-deprotonated forms, and the atom- and electron-transfer efficiency. The role of the catechol moiety and the 3-OH group of quercetin as scavengers of different types of free radicals (CH3OO•, CH3O•, •OH, and •CH2OH) is rationalized. Identifying the exact mechanism and accurately evaluating kinetics is of fundamental importance to understand antioxidant behavior in physiological environments.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp3116319