title: Glutathione and the antioxidant potential of binary mixtures with flavonoids: synergisms and antagonisms.
abstract: Polyphenols are able to trap free radicals, which contributes to their known antioxidant capacity. In plant extracts, these secondary metabolites may act in concert, in a way that their combined activities will be superior to their individual effects (synergistic interaction). Several polyphenols have demonstrated clear antioxidant properties in vitro, and many of their biological actions have been attributed to their intrinsic reducing capabilities. As so, the intake of these compounds at certain concentrations in the diet and/or supplementation may potentiate the activity of reduced form glutathione (GSH), thus better fighting oxidative stress. The aim of this work was to predict a structure-antioxidant activity relationship using different classes of flavonoids and to assess, for the first time, possible synergisms and antagonisms with GSH. For these purposes a screening microassay involving the scavenging of DPPH• was applied. In general, among the tested compounds, those lacking the catechol group in B ring showed antagonistic behaviour with GSH. Myricetin displayed additive effect, while quercetin, fisetin, luteolin, luteolin-7-O-glucoside, taxifolin and (+)-catechin demonstrated synergistic actions. Furthermore, adducts formed at C2' and C5' of the B ring seem to be more important for the antioxidant capacity than adducts formed at C6 and C8 of the A ring.
authors.affiliation: REQUIMTE/Laboratório de Farmacognosia, Departamento de Química, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, nº 228, 4050-313 Porto, Portugal.
authors.forename: Renato B
authors.initials: RB
authors.lastname: Pereira
authors.forename: Carla
authors.initials: C
authors.lastname: Sousa
authors.forename: Andreia
authors.initials: A
authors.lastname: Costa
authors.forename: Paula B
authors.initials: PB
authors.lastname: Andrade
authors.forename: Patrícia
authors.initials: P
authors.lastname: Valentão
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry; D005978:Glutathione / Q000037:antagonists & inhibitors / Q000737:chemistry*; D018384:Oxidative Stress; D010636:Phenols / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D016166:Free Radical Scavengers; D010636:Phenols; C040015:myricetin; D005978:Glutathione
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