Redox properties of individual quercetin moieties
Language English Country United States Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
PubMed
31381971
DOI
10.1016/j.freeradbiomed.2019.08.001
PII: S0891-5849(19)30897-4
Knihovny.cz E-resources
- Keywords
- Antiradical properties, Benzofuranone, Electron transfer, Electronic structure, Quercetin oxidation, Redox properties, Stability,
- MeSH
- Antioxidants chemistry MeSH
- Oxidation-Reduction MeSH
- Quercetin chemistry MeSH
- Free Radical Scavengers chemistry MeSH
- Structure-Activity Relationship MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Antioxidants MeSH
- Quercetin MeSH
- Free Radical Scavengers MeSH
Quercetin is one of the most prominent and widely studied flavonoids. Its oxidation has been previously investigated only indirectly by comparative analyses of structurally analogous compounds, e.g. dihydroquercetin (taxifolin). To provide direct evidence about the mechanism of quercetin oxidation, we employed selective alkylation procedures for the step-by-step blocking of individual redox active sites, i.e. the catechol, resorcinol and enol C-3 hydroxyls, as represented by newly prepared quercetin derivatives 1-3. Based on the structure-activity relationship (SAR), electrochemical, and computational (density functional theory) studies, we can clearly confirm that quercetin is oxidized in the following steps: the catechol moiety is oxidized first, forming the benzofuranone derivative via intramolecular rearrangement mechanism; therefore the quercetin C-3 hydroxy group cannot be involved in further oxidation reactions or other biochemical processes. The benzofuranone is oxidized subsequently, followed by oxidation of the resorcinol motif to complete the electrochemical cascade of reactions. Derivatization of individual quercetin hydroxyls has a significant effect on its redox behavior, and, importantly, on its antiradical and stability properties, as shown in DPPH/ABTS radical scavenging assays and UV-Vis spectrophotometry, respectively. The SAR data reported here are instrumental for future studies on the oxidation of biologically or technologically important flavonoids and other polyphenols or polyhydroxy substituted aromatics. This is the first complete and direct study mapping redox properties of individual moieties in quercetin structure.
Department of Chemistry University of Ioannina Ioannina 45110 Greece
INSERM U1248 Univ Limoges 2 rue du Docteur Marcland 87025 Limoges France
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