Electrochemical Oxidation of Quercetin

Oliveira-Brett, Ana Maria; Ghica, Mariana Emilia

doi:10.1002/elan.200302800

Cited by 260 publications

(170 citation statements)

References 12 publications

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“…It turned out (Table 1) that among the investigated flavonoids, quercetin is the strongest antioxidant, which is consistent with the available literature data (RiceEvans et al 1996). Quercetin is characterized by the smallest half-wave potential (i.e., potential at which the wave current is equal to one half of its maximum current) and the highest chromatographic peaks, particularly the peak obtained at 0.1 V. At higher potentials, the additional waves are observed, similarly to the voltammetric results (Brett and Ghica 2003). Quercetin is also the best electron donor from all investigated flavonoids.…”

Section: Resultssupporting

confidence: 70%

Comparative Analysis of Antioxidative Activity of Flavonoids Using HPLC–ED and Photometric Assays

et al. 2013

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The present investigation reports on the application of a new antioxidant activity assay for the examination of flavonoids. It has been shown that the high-performance liquid chromatography with electrochemical detection (HPLC-ED) measurements allow to obtain additional information about the antioxidative properties of pure compounds by measuring their half-wave potential, the chromatographic peak height, and the product of the peak height and exponent of potential. In comparison to the classical electrochemical measurements, the HPLC-ED is characterized by a much smaller detection limit. The results were compared with the standard photometric measurement based on 1,1-diphenyl-2-picrylhydrazyl radicals. The possible antioxidant activity forecasting is also discussed.

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Section: Resultssupporting

confidence: 70%

Comparative Analysis of Antioxidative Activity of Flavonoids Using HPLC–ED and Photometric Assays

et al. 2013

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“…According to the literature related to studies with flavonoids, the first oxidation peak observed in the 2-SC 1A-1D corresponds to the oxidation of the 3 0 ,4 0 -OH (catechol) moiety in the B-ring. [16][17][18] The absence of a similar peak in the compounds lacking this catechol substituent supports this thesis. A detailed analysis of this peak indicated a reversible redox process with a coupled chemical reaction, also in accordance to previous reports for flavonoids.…”

Section: Discussionsupporting

confidence: 72%

“…This technique has been used to study the electrochemical oxidation mechanisms of flavonolic compounds. [16][17][18] The purpose of the present study was to use cyclic voltammetry to assess the electrochemical behaviour of different 2-SC (Table 1) in order to understand the mechanism behind the scavenging of ROS and RNS. Five flavones (luteolin, apigenin, chrysin, 5-hydroxyflavone and 7-hydroxyflavone) were also tested due to the similarities of their structures with those of 2-SC.…”

Section: Introductionmentioning

confidence: 99%

Cyclic voltammetric analysis of 2-styrylchromones: Relationship with the antioxidant activity

Gomes¹,

Fernandes²,

Garcia³

et al. 2008

Bioorganic & Medicinal Chemistry

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a b s t r a c t 2-Styrylchromones (2-SC) are a chemical family of oxygen heterocyclic compounds, vinylogues of flavones (2-phenylchromones), whose occurrence in nature has been reported. Recently, several 2-SC derivatives were demonstrated to have antioxidant properties, namely, xanthine oxidase inhibition, hepatoprotection against pro-oxidant agents in cellular and non-cellular systems and scavenging activity against reactive oxygen and reactive nitrogen species (ROS and RNS). Considering these antioxidant properties, it may be hypothesised that the electrochemical redox behaviour of 2-SC contributes significantly to their activity. To test this hypothesis, the electrochemical behaviour of different 2-SC was studied, together with a number of flavonoids with well-known antioxidant activities, by cyclic voltammetry, and the results correlated to their ability to scavenge ROS and RNS.The results obtained showed that 2-SC with a catecholic B-ring have a low oxidation peak potential corresponding to the oxidation of the 3 0 ,4 0 -OH (catechol) moiety. The compounds with a phenolic B-ring have a common peak, with oxidation potential values of about +0.4/+0.5 V versus Ag/AgCl, corresponding to the oxidation of the 4 0 -OH. The oxidation of the hydroxyl substituents in the A-ring generated peaks of higher potentials (+0.7/+0.8 V vs Ag/AgCl). The results from the scavenging assays were in agreement with those obtained from the cyclic voltammetry, that is, higher scavenging effects corresponded to lower values of oxidation potentials, with significant correlation coefficients. The values obtained for the studied flavonoids are in accordance with the literature, and reflect their relative antioxidant activity, when compared to the studied 2-SC. Thus, in this family of compounds, oxidation potentials obtained by cyclic voltammetry seem to be applicable as a general indicator of radical scavenging activity.

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“…The overall cyclic voltammogram profile is similar to those previously reported. 13,14,16,17 In general, it has been proposed that the charge transfer process at peak I corresponds to the oxidation of the 3',4'-dihydroxy substitute on B-ring of quercetin, while the peaks II and III comprise oxidation reactions involving the hydroxyl group at C-3 and the 5,7-dihydroxy substitutes on A-ring, respectively. Depending on the experimental conditions, the corresponding reduction reactions were evidenced (see below).…”

Section: Controlled-potential Electrolysis and Characteristics Of Oximentioning

confidence: 99%

“…13 The electrochemistry of quercetin, in particular, besides not being very understood, reveals contradictions on both the oxidation products and the reversibility of the reactions. For instance, a limited extent of data available in the pertinent literature suggests that the oxidation of quercetin yields to the corresponding ortho-quinone as product, which is an unstable compound that could undergo homogeneous chemical reactions such as intramolecular rearrangements [13][14][15][16] or addition reactions when in presence of nucleophiles. 17 Therefore, the presence of water and/or ethanol (nucleophiles) in the solution may thus have very important implications for the oxidation mechanism and in turn for the antioxidant activity, since water was found to act as catalysts in reactions subsequent to the formation of ortho-quinones.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical oxidation of quercetin in hydro-alcoholic solution

Timbola¹,

Souza²,

Giacomelli³

et al. 2006

J. Braz. Chem. Soc.

132

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O comportamento eletroquímico da quercetina em meio hidro-alcoólico foi estudado na faixa de pH 2,2-9,2 aplicando-se as técnicas voltametria cíclica, eletrólise com potencial controlado e espectroscopia UV-Vis. Voltamogramas cíclicos para a quercetina mostraram três picos de oxidação e um pico de redução dependente das condições experimentais. Um processo de oxidação envolvendo dois prótons e dois elétrons no primeiro pico conduziu à formação da orto-quinona correspondente, a qual é uma espécie eletroquimicamente ativa e instável, como evidenciado pela dependência do perfil dos voltamogramas cíclicos com a velocidade de variação de potencial, em concordância com um mecanismo do tipo eletroquímico-químico (EC). Eletrólises com potencial controlado geraram três produtos caracterizados por espectroscopia UV-Vis. Um esquema reacional envolvendo as etapas eletroquímica e química foi proposto para a eletro-oxidação da quercetina em solução hidro-alcoólica, com base em dados obtidos da literatura e em evidências experimentais.The electrochemistry of quercetin hydro-alcoholic solutions of pH 2.2 to 9.2 was studied by cyclic voltammetry, controlled-potential electrolysis and UV-Vis spectroscopy. Cyclic voltammograms for quercetin showed three oxidation peaks and one reduction peak depending on the experimental conditions. The two-electron two-proton oxidation process at the first peak led to the formation of the corresponding ortho-quinone, which is an electrochemically active and unstable species, as evidenced by the dependence of the cyclic voltammogram profile on the applied scan rate, in agreement with the EC mechanism. Controlled-potential electrolysis yielded three products as characterized by UV-Vis spectroscopy. A reaction scheme comprising electrochemical and chemical steps was proposed for the electro-oxidation of the quercetin in hydro-alcoholic solutions on basis of experimental evidences obtained in this work and elsewhere.

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Electrochemical Oxidation of Quercetin

Cited by 260 publications

References 12 publications

Comparative Analysis of Antioxidative Activity of Flavonoids Using HPLC–ED and Photometric Assays

Comparative Analysis of Antioxidative Activity of Flavonoids Using HPLC–ED and Photometric Assays

Cyclic voltammetric analysis of 2-styrylchromones: Relationship with the antioxidant activity

Electrochemical oxidation of quercetin in hydro-alcoholic solution

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