title: Free radical scavenging potency of quercetin catecholic colonic metabolites: Thermodynamics of 2H+/2e-processes.
abstract: Reaction energetics of the double (2H+/2e-), i.e., the first 1H+/1e-(catechol→ phenoxyl radical) and the second 1H+/1e-(phenoxyl radical→ quinone) free radical scavenging mechanisms of quercetin and its six colonic catecholic metabolites (caffeic acid, hydrocaffeic acid, homoprotocatechuic acid, protocatechuic acid, 4-methylcatechol, and catechol) were computationally studied using density functional theory, with the aim to estimate the antiradical potency of these molecules. We found that second hydrogen atom transfer (HAT) and second sequential proton loss electron transfer (SPLET) mechanisms are less energy demanding than the first ones indicating 2H+/2e-processes as inherent to catechol moiety. The Gibbs free energy change for reactions of inactivation of selected free radicals indicate that catecholic colonic metabolites constitute an efficient group of more potent scavengers than quercetin itself, able to deactivate various free radicals, under different biological conditions. They could be responsible for the health benefits associated with regular intake of flavonoid-rich diet.
authors.affiliation: Department of Biology, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8a, 31000 Osijek, Croatia.
authors.forename: Ana
authors.initials: A
authors.lastname: Amić
authors.affiliation: Ruđer Bošković Institute, Bijenička 54, 10002 Zagreb, Croatia.
authors.forename: Bono
authors.initials: B
authors.lastname: Lučić
authors.affiliation: Ruđer Bošković Institute, Bijenička 54, 10002 Zagreb, Croatia.
authors.forename: Višnja
authors.initials: V
authors.lastname: Stepanić
authors.affiliation: Department of Chemical-Technological Sciences, State University of Novi Pazar, Vuka Karadžića bb, 36300 Novi Pazar, Serbia.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Marković
authors.affiliation: Faculty of Science, University of Kragujevac, Radoja Domanovića 12, 34000 Kragujevac, Serbia.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Marković
authors.affiliation: Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia.
authors.forename: Jasmina M
authors.initials: JM
authors.lastname: Dimitrić Marković
authors.affiliation: Faculty of Agriculture, Josip Juraj Strossmayer University of Osijek, Kralja Petra Svačića 1d, 31000 Osijek, Croatia. Electronic address: damic@pfos.hr.
authors.forename: Dragan
authors.initials: D
authors.lastname: Amić
mesh_terms: D003903:Deuterium / Q000737:chemistry*; D004579:Electron Transport / Q000502:physiology; D016166:Free Radical Scavengers / Q000737:chemistry / Q000378:metabolism*; D005609:Free Radicals / Q000737:chemistry / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry; D010084:Oxidation-Reduction; D011522:Protons; D011794:Quercetin / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D016166:Free Radical Scavengers; D005609:Free Radicals; D011522:Protons; D006859:Hydrogen; D011794:Quercetin; D003903:Deuterium
keywords: Catecholic compounds; Colonic metabolites; Double HAT; Double SPLET; Quercetin; Radical scavenging