Electrochemistry of catechol-containing flavonoids

Hendrickson, Howard P.; Kaufman, Arlen D.; Lunte, Craig E.

doi:10.1016/0731-7085(94)90007-8

Cited by 188 publications

(153 citation statements)

References 5 publications

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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%

“…Besides, the results reveal that the oxidation processes at peaks II and III do not correspond to the oxidation of the hydroxyl group present in C-3 and of the substitute 5,7-dihydroxy (A-ring), respectively, as suggested by some authors. 13,14,17 If it was the case, the peaks II and III would not be dependent on v, because the reactions would happen regardless of the time of analysis. Furthermore, a reduction peak (IV) associated to peak I was found to be dependent on v (see below).…”

Section: Influence Of Scan Ratementioning

confidence: 99%

“…Quercetin (spectrum a) exhibits two absorption bands at 257 and 373 nm referring to conjugations in the B-ring and A-ring, respectively. [13][14][15] Upon electrolysis (spectrum b), a new absorption band appears around 290 nm, while the bands at 257 and 373 nm exhibited lower intensities. After the purification step (spectrum c), the absorption band at 373 nm became less pronounced and the absorption band in 257 nm practically disappeared.…”

Section: Temperature (~ 2 O C) After a Given Period Of Time (96 H)mentioning

confidence: 99%

“…The spectrum recorded for fraction B ( Figure 9B) showed an absorption band at 293 nm and a shoulder at 321 nm. This profile has been attributed to decreased conjugation [13][14][15] and presence of a quinonoid structure as chromophore. 23 Finally, only a single absorption band at 293 nm is observed in the spectrum corresponding to fraction C (the most polar one) ( Figure 9C).…”

Section: Temperature (~ 2 O C) After a Given Period Of Time (96 H)mentioning

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%

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Electrochemical oxidation of quercetin in hydro-alcoholic solution

Timbola¹,

Souza²,

Giacomelli³

et al. 2006

J. Braz. Chem. Soc.

135

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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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Section: Controlled-potential Electrolysis and Characteristics Of Oximentioning

confidence: 99%

Section: Influence Of Scan Ratementioning

confidence: 99%

Section: Temperature (~ 2 O C) After a Given Period Of Time (96 H)mentioning

confidence: 99%

Section: Temperature (~ 2 O C) After a Given Period Of Time (96 H)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Electrochemical oxidation of quercetin in hydro-alcoholic solution

Timbola¹,

Souza²,

Giacomelli³

et al. 2006

J. Braz. Chem. Soc.

135

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Flavonoids quercetin, myricetin, kaemferol and (+)-catechin as antioxidants in methyl linoleate

Pekkarinen

Heinonen

Hopia

1999

J. Sci. Food Agric.

130

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Automated Voltammetric Determination of Reducing Compounds in Beer

1998

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Different types of reductones have a considerable influence on the stability of beer. They can be determined indirectly using the redox dyestuff 2,6-dichlorophenol-indophenol. Its reduced form is electrochemically reoxidized, followed by internal calibration with an ascorbic acid standard. Varying the reaction time of dyestuff and reductones can reveal additional information on the composition of reductones. This work describes an automated method to determine the reducing power of beer and gives potential applications in quality control.

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Electrochemistry of catechol-containing flavonoids

Cited by 188 publications

References 5 publications

Electrochemical oxidation of quercetin in hydro-alcoholic solution

Electrochemical oxidation of quercetin in hydro-alcoholic solution

Flavonoids quercetin, myricetin, kaemferol and (+)-catechin as antioxidants in methyl linoleate

Automated Voltammetric Determination of Reducing Compounds in Beer

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