Single or double hydrogen atom transfer in the reaction of metal – Associated phenolic acids with •OH radical: DFT study

Fifen, Jean Jules; Nsangou, Mama; Dhaouadi, Zoubeida; Motapon, Ousmanou; Lahmar, S.

doi:10.1016/j.theochem.2008.12.046

Cited by 18 publications

(17 citation statements)

References 49 publications

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“…It is evident from Figure 4 that, in gas phase, the presence of the metal ions leads to a great increment in the IP value of juglone. This result agrees with those obtained by other authors in similar studies [9,26]. In gas phase, the Cu(I) chelate has the lowest IP value (12.74 eV).…”

Section: Electron Transfer-proton Transfer Mechanismsupporting

confidence: 93%

“…It is clear from this figure that the BDE and BDFE values of the chelates are lower than that of juglone in the two media investigated. This is a clear indication of the fact that the presence of these metal ions increases the AOA of juglone, which is in good agreement with the findings in the literature [9,26]. In gas phase, the Co(II) chelate has been found to possess the lowest BDE value (262 kJ/mol), which corroborates with its highest O-H bond length observed in the said phase (Section 3.3).…”

Section: Radical Scavenging Activitysupporting

confidence: 90%

“…With the aim of determining the nature of all the stationary points, frequency calculations were performed on all the optimized geometries at the same level of theory. The DFT/B3LYP method was used because it is frequently employed for the studies on metalation of natural antioxidant [9][10][11]26]. The calculations on closed shell systems were performed by the means of the Restricted Kohn-Sham formalism whereas the Unrestricted Kohn-Sham approach was used for open shell systems [23,27].…”

Section: Theoretical Background and Computational Detailsmentioning

confidence: 99%

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Quantum Chemical Investigation on the Antioxidant Activity of Neutral and Anionic Forms of Juglone: Metal Chelation and Its Effect on Radical Scavenging Activity

Tamafo

Ghogomu

Nkungli

et al. 2017

Journal of Chemistry

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The chelation ability of divalent Mg, Ca, Fe, Co, Ni, Cu, Zn, and monovalent Cu ions by neutral and anionic forms of juglone has been investigated at DFT/B3LYP/6-31+G(d,p) level of theory in gas and aqueous phases. It is noteworthy that only the 1 : 1 stoichiometry was considered herein. The effects of these metals on the radical scavenging activity of neutral juglone were evaluated via the usual descriptors of hydrogen atom transfer. According to our results, metal chelation by the two forms of juglone was spontaneous and exothermic in both media. Based on the binding energies, Cu(II) ion showed the highest affinity for the ligands. QTAIM analyses identified the metal-ligand bonds as intermediate type interactions in all the chelates, except those of Ca and Mg. It was also found that the chelates were better radical scavengers than the ligands. In the gas phase, the scavenging activity of the compounds was found to be governed by direct hydrogen atom transfer, the Co(II) chelate being the most reactive. In the aqueous phase also, the sequential proton loss electron transfer was preferred by all the molecules, while the Cu(II) chelates were the most reactive.

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Section: Electron Transfer-proton Transfer Mechanismsupporting

confidence: 93%

Section: Radical Scavenging Activitysupporting

confidence: 90%

Section: Theoretical Background and Computational Detailsmentioning

confidence: 99%

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Quantum Chemical Investigation on the Antioxidant Activity of Neutral and Anionic Forms of Juglone: Metal Chelation and Its Effect on Radical Scavenging Activity

Tamafo

Ghogomu

Nkungli

et al. 2017

Journal of Chemistry

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“…Therefrom, it is noteworthy that the scavenging of hydroxyl radical by 3,4-DHPPA passes through a transition state (TS) while that of OBr − anion is barrierless. Moreover, it is well-known that the reaction of a phenolic acid (PhA) with neutral ROS leads to PCET mechanism while that with negatively charged ROS undergoes a barrierless PT mechanism [3,12,18,43,44]. This result may be generalized to PhAs which only have carbon, oxygen, and hydrogen in their skeleton (e.g., Quercetin may be a good candidate) and are involving the same RS or other.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the results obtained involving 3,4-DHPPA could be generalized to Quercetin. Moreover, metal ions effects on the antioxidant activity of 3,4-DHPPA were studied in the vacuum [18]. A conformational study of this acid was also undertaken [3] and the likeliest conformer is depicted in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Proton-Coupled Electron Transfer in the Reaction of 3,4-Dihydroxyphenylpyruvic Acid with Reactive Species in Various Media

Fifen

Dhaouadi

Nsangou

et al. 2015

International Journal of Chemical Physics

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The distinction of concerted proton-coupled electron transfer (CPCET) from sequential one as well as proton transfer-electron transfer (PT-ET) from electron transfer-proton transfer (ET-PT) in the O-H bond cleavage reactions in various media has always been a difficult task. In this work, the activation barrier of the CPCET mechanism, its rate constants, and reaction free energies related to ET-PT and PT-ET involving coreactive species were presented as good parameters to attempt the problem. DFT calculations were carried out studying the described pathways subsequent to the scavenging of• OH and OBr − by the 3,4-DHPPA in various media. The solvation was described in a hybrid manner using IEF-PCM model conjointly with a model that takes into account some solute-solvent interactions. As a result, we found that the scavenging of hydroxyl radical by 3,4-DHPPA is thermodynamically governed by a one-step hydrogen atom transfer (CPCET) from the acid to the radical in all media. In kinetic viewpoint, CPCET still dominates in the vacuum and in nonpolar solvents, but in polar solvents it could compete strongly with the ET-PT mechanism so that the latter could slightly dominate.

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DFT study of the effect of solvent on the H-atom transfer involved in the scavenging of the free radicals ●HO2 and ●O2 − by caffeic acid phenethyl ester and some of its derivatives

et al. 2014

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H-atom transfer from caffeic acid phenethyl ester (CAPE), MBC (3-methyl-2-butenyl caffeate), BC (benzoic caffeate), P3HC (phenethyl-3-hydroxycinnamate), and P4HC (phenethyl-4-hydroxycinnamate) to the selected free radicals (·)HO2 and (·)O2(-) was studied. Such a transfer can proceed in three different ways: concerted proton-coupled electron transfer (CPCET), electron transfer followed by proton transfer (ET-PT), and proton transfer followed by electron transfer (PT-ET). The latter pathway is sometimes competitive with SPLET (sequential proton loss electron transfer) in polar media. Analyzing the thermodynamic descriptors of the reactions of CAPE and its derivatives with co-reactive species-in particular, the free energies of reactions, the activation barrier to the CPCET mechanism, and their rate constants-appears to be the most realistic method of investigating the H-atom transfers of interest. These analyses were performed via DFT calculations, which agree well with the data acquired from experimental studies (IC50) and from CBS calculations. The CPCM solvation model was used throughout the work, while the SMD model-employed as a reference-was used only for CAPE. The main conclusion drawn from the analysis was that SPLET is the mechanism that governs the reaction of phenolic acids with (·)HO2, while PT-ET governs the reaction of phenols with (·)O2(-). In kinetic investigations of the CPCET process, the rate constant decreases as the solvent polarity increases, so the reaction velocity slows down.

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Single or double hydrogen atom transfer in the reaction of metal – Associated phenolic acids with •OH radical: DFT study

Cited by 18 publications

References 49 publications

Quantum Chemical Investigation on the Antioxidant Activity of Neutral and Anionic Forms of Juglone: Metal Chelation and Its Effect on Radical Scavenging Activity

Quantum Chemical Investigation on the Antioxidant Activity of Neutral and Anionic Forms of Juglone: Metal Chelation and Its Effect on Radical Scavenging Activity

Proton-Coupled Electron Transfer in the Reaction of 3,4-Dihydroxyphenylpyruvic Acid with Reactive Species in Various Media

DFT study of the effect of solvent on the H-atom transfer involved in the scavenging of the free radicals ●HO2 and ●O2 − by caffeic acid phenethyl ester and some of its derivatives

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