Zinc catechin complexes in aprotic medium. Redox chemistry and interaction with superoxide radical anion |
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| Affiliation: | 1. Departamento Quı́mica Inorgánica, Facultad de Quı́mica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Santiago, Chile;2. Departamento Quı́mica Orgánica, Facultad de Quı́mica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Santiago, Chile;3. Laboratorio de Citologı́a, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Santiago, Chile;1. Organic Chemistry Laboratory, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany;2. Department of Genetics, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany;1. Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Leninskii pr. 31, Moscow 119991, Russia;2. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, Obrucheva st. 40, Moscow 117342, Russia;1. Laboratoire Toxlab, 75018 Paris, France;2. Unité médicojudiciaire de l’Hôtel-Dieu, 75004 Paris, France;3. Département d’anesthésie-réanimation, CHU Necker, 75015 Paris, France;1. Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China;2. Chemical Engineering Research Center, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China |
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| Abstract: | The redox chemistry of catechin and its zinc(II) complexes has been studied in dimethyl sulfoxide. In the absence of base, catechin undergoes oxidation processes at 0.96 and 1.24 V versus SCE. The first process corresponds to the formation of the quinonic form of the catechol moiety. In the presence of 1 equiv. of base, a stable 1:2 complex is formed with oxidation processes that show up at 0.26 and 0.62 V versus SCE. The voltammetric and spectroscopic characterization of the species produced after the oxidation processes are described. Upon interaction of the complex with superoxide radical anion in dimethyl sulfoxide, its basic character causes the formation of the monoanion of catechin leading to a more stable zinc(II) complex. Protonated superoxide disproportionates to molecular oxygen and peroxide leading to oxidation of the bound ligand. Upon complexation the oxidation potentials decrease, favoring thermodynamically the antioxidant action of this flavonoid. |
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