Electrochemical oxidation of flavonoids: PM6 and DFT for elucidating electronic changes and modelling oxidation potential

Miličević, Ante; Miletić, Goran; Jovanović, Ivana

doi:10.1016/j.molliq.2019.04.128

Cited by 10 publications

(23 citation statements)

References 29 publications

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“…As previously stated [1][2][3][4], an improvement of all of the models was obtained by adding the number of OH groups (NOH) on a flavonoid skeleton as a variable to quadratic regressions. The statistics for all of the models mentioned were significantly improved, but again, the model using ring were taken into account, which enabled us to obtain much better statistics for all of the models.…”

Section: Resultsmentioning

confidence: 99%

“…= 0.031 and S.E.cv = 0.037 (N = 29). The introduction of pH as a variable[1][2][3][4] allowed the estimation of Ep1 values at pHs of both 3 and 7 (N = 58), and the statistics obtained by mean variable was of similar quality; R 2 = 0.982, S.E. = 0.039 and S.E.cv = 0.043 (Fig.4).…”

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confidence: 80%

“…Earlier [2][3][4] we developed a model based on the sum of atomic orbital spin populations over the carbon atoms in the skeleton of a flavonoid radical molecule, s(C)  AOSPRad. A comparison of our models with the model using hydrogen bond dissociation energy (BDE), which is one of the most important variables for antioxidant activity modeling [5,6], showed inferiority of the BDE model for estimating Ep1 values [1][2][3][4]. In this study, I used the same set of 29 flavonoids as in Ref.…”

Section: Introductionmentioning

confidence: 99%

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Application of Changes in Atomic Charges Resulting from Different Electrochemical Oxidation Mechanisms for the Estimation of the First Oxidation Potential of Flavonoids

Miličević¹

2022

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In addition to our model based on the sum of the differences in the net atomic charges between a cation and a neutral flavonoid ( s(C)  ΔNACCat-Neut) over the carbon atoms in the flavonoid skeleton, here I present two complementary models for the estimation of the first electrochemical oxidation potential, Ep1. The models were also based on the sum of differences in the net atomic charges, but between other species of a flavonoid; between a radical and an anion of a flavonoid, s(C)  ΔNACRad-Anion, and between a radical and a neutral flavonoid, s(C)  ΔNACRad-Neut. These three variables are connected with different mechanisms (SET-PT, SPLET and HAT) of electron loss during the electrochemical oxidation of a flavonoid. It was shown that the best model for the given set of 29 flavonoids was obtained by using mean values of all of the three variables as a variable (R 2 = 0.974, S.E. = 0.042 and S.E.cv = 0.45) which could mean that all three mechanisms are equally possible.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

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Application of Changes in Atomic Charges Resulting from Different Electrochemical Oxidation Mechanisms for the Estimation of the First Oxidation Potential of Flavonoids

Miličević¹

2022

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“…The number of oxidation peaks and the values of their potentials depend greatly on structure of the flavonoid and solvent. The first oxidation potentials of the series of flavonoids in water solutions were determined by means of square-wave voltammetry [9][10][11][12]. However, the mechanistic aspects of the processes have not been discussed.…”

Section: Introductionmentioning

confidence: 99%

“…To date, the electrochemical behavior of flavonoids has been mainly studied in water buffer solution [10][11][12][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] or in hydroalcoholic media [31][32][33][34][35][36]. In waterbased solutions, the potential and reversibility of the first oxidation peak are scan rate dependent and pH dependent.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Investigation of some Flavonoids in Aprotic Media

Naróg

Sobkowiak

2022

Electroanalysis

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Cyclic voltammerty data for the oxidation of 15 flavonoids in acetonitrile have been presented. Up to three peaks in different potential regions appear in the CV curves, depending on the structure of a flavonoid. The peak in the first potential region (+0.79÷+1.03 V vs SCE) occurs when a flavonoid molecule has an o‐dihydroxy moiety in the ring A or B. From the data in the literature, the formation of o‐quinone is responsible for the occurrence of the peak. When the o‐dihydroxy moiety is in ring B and the hydroxyl group is at position 3, the second peak in the potential region+1.08÷+1.32 V, is present. It is an agreement that the peak is due to oxidation of benzofuranone derivative formed in reaction of o‐quinone with water. Molecules with an o‐quinone moiety located in ring A seem to be less reactive, and the peak in the second potential region does not occur. However, the existence of an o‐quinone in the ring B is not necessary for the peak in the second potential region to be present. The oxidation of kaempferol and morin, which have hydroxyl groups at positions 3 and 4’, takes place at 0.98 V and 0.97 V, respectively, and leads to the formation of p‐quinone methide. We have shown that the peak in the second potential region also appears when the hydroxyl group in the flavonoid molecule is only at position 3 or at position 4’. For 3‐hydroxyflavone and apigenin, which are oxidized at +1.10 V and 1.49 V respectively, p‐quinone methide was detected after controlled potential bulk electrolysis. A mechanism which includes the reaction of the carbon radical with a trace of water has been proposed. For flavonoids that have an o‐dihydroxy moiety in ring B and the hydroxyl group at position 3, two oxidation peaks are observed in the CV curves in the second potential region for low scan rates (below 0.1 V s−1). An explanation of this behavior has been proposed.

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