Concerted two-proton–coupled electron transfer from catechols to superoxide via hydrogen bonds

Nakayama, Tatsushi; Uno, Bunji

doi:10.1016/j.electacta.2016.05.034

Cited by 32 publications

(74 citation statements)

References 45 publications

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“…In the present study, we chose to examine the variation of cathodic peak currents at the EC 50 and zero concentrations ( I 50 pc / I 0 pc ). However, it should be highlighted that several of these compounds registered large pre‐peaks in their voltammograms, and were thus exempted from the aforementioned measurements as they are possibly implicated in a sequence of mechanistic processes which are not at present fully understood; although it has been suggested that these might involve a concerted proton‐coupled electron transfer process . Regardless, in these instances, as described by René et al., an approximate classification was instead performed by considering the difference in the potential (ΔE) of the pre‐peak (when its intensity was half that of O 2 reduction) and the peak of the initial O 2 reduction .…”

Section: Resultsmentioning

confidence: 99%

“…In addition, O 2 .− has also been demonstrated to be relatively long‐lived and easily handled in such media, while changes that occur during its reactions (such as consumption of O 2 .− or analyte) may be monitored in situ . For example, there have been a number of studies that have examined the reactions between electrochemically generated O 2 .− and various groups of natural and synthetic compounds such as flavonoids, (poly)phenols, and others . More specifically, by carefully analyzing the changes in the profiles of the voltammograms obtained for O 2 reduction upon the addition of a substrate, such as the anodic and cathodic peak current intensities, a comparison of relative reactivities across different analytes, and the elucidation of general scavenging mechanisms involved can be made …”

Section: Introductionmentioning

confidence: 99%

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Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

et al. 2017

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Superoxide (O2.−), an anionic radical of the reactive oxygen species (ROS) family, is continuously produced in the body and can lead to the undesirable modification and damage of important biological molecules. In the present study, the relative reactivities of 18 food and vitamin molecules toward electrochemically generated O2.− were investigated in N,N‐dimethylformamide (DMF) solutions by using cyclic voltammetry (CV). The quenching of O2.− was measured by monitoring the decreases in the anodic currents of the reverse peaks after the one‐electron reduction of molecular oxygen (O2), while systematically increasing the concentration of the test substrates. The reactivity of each compound was then approximated and compared using effective concentration indexes, EC10 and EC50, which represent the amount of compound required to reduce the concentration of the electrochemically generated O2.− by 10 and 50%, respectively, under the present conditions. Where possible, the likely mechanisms that are involved in the scavenging of O2.− are also discussed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

et al. 2017

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“…Several reaction mechanisms for O 2 •− elimination by acidic substrates such as 5-ASA are known, including the superoxide-facilitated oxidation (SFO) [ 6 , 7 , 8 ], hydrogen–atom transfer (HAT) involving proton-coupled electron transfer (PCET) [ 9 , 10 , 11 , 12 , 13 ], and sequential proton-loss electron transfer (SPLET) [ 14 ]. In the SFO mechanism, the initial proton transfer (PT) from the substrate to O 2 •− to give HO 2 • is followed by rapid dismutation to give H 2 O 2 and O 2 .…”

Section: Introductionmentioning

confidence: 99%

Electrochemical and Mechanistic Study of Superoxide Elimination by Mesalazine through Proton-Coupled Electron Transfer

Nakayama

Honda

2021

Pharmaceuticals

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The elimination of superoxide radical anions (O2•−) by 5-amino-2-hydroxybenzoic acid (mesalazine, 5-ASA), 4-amino-2-hydroxybenzoic acid (4-ASA), and related compounds used for ulcerative colitis treatment was investigated using cyclic voltammetry and electron spin resonance (ESR) analyses aided by density functional theory (DFT) calculations. Quasi-reversible O2/O2•− redox was found to be modified by the compounds, suggesting that an acid–base reaction in which a hydroperoxyl radical (HO2•) is formed from O2•− occurs. However, the deprotonated 5-ASA anion can eliminate O2•− through proton-coupled electron transfer (PCET), forming a radical product. This electron transfer (ET) was confirmed by ESR analysis. The 4-aminophenol moiety in 5-ASA plays an important role in the PCET, involving two proton transfers and one ET based on π-conjugation. The electrochemical and DFT results indicated that O2•− elimination by 5-ASA proceeds efficiently through the PCET mechanism after deprotonation of the 1-carboxyl group. Thus, 5-ASA may act as an anti-inflammatory agent in the alkali intestine through PCET-based O2•− elimination.

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“…Due to the immense importance and implications of this toxicant, another area of interest has been the voltammetric examination of the reactions between electrochemically generated O 2 .− and different classes of molecules and substances. Included in this discipline of study have primarily been works directed toward the examination of scavenging capabilities of prevalent antioxidant molecules such as flavonoids and (poly)phenolic compounds ,. However, because these compounds are often constituted of complex chemical structures comprising of multiple functional groups, it can sometimes be challenging to unravel the exact characteristic or facet responsible for the perceived reactivity or lack thereof.…”

Section: Introductionmentioning

confidence: 99%

Comparing the Relative Reactivities of Structurally Varied Alcohols toward Electrochemically Generated Superoxide

et al. 2017

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is a free-radical anion of the reactive oxygen species (ROS) family. In the present study, the relative reactivities of 14 structurally varied aliphatic alcohols toward electrochemically generated O 2 * À were investigated in solutions of N,Ndimethylformamide by using cyclic voltammetry (CV). Upon the stepwise addition of each substrate, the chemical reversibility of the one-electron voltammetric reduction of the dioxygen (O 2 ) to O 2 * À was found to decrease, which enabled the extent of radical inhibition to be determined by measuring the resultant oxidative peak current (I pa ) magnitudes on the reverse scan of the CV. Based on the electrochemical responses gathered, best fit plots of the percentage decrease in the anodic peak current (%DI pa ) against the concentration of substrate added were obtained and compared according to the different classes of alcohols that were examined (linear, fluorinated, branched, and poly-hydroxylated). In addition, different parameters, such as electronic effects, steric effects, degree of hydroxylation, and kinetic effects that affect the O 2 * À scavenging abilities of the alcohols, are also discussed.

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Concerted two-proton–coupled electron transfer from catechols to superoxide via hydrogen bonds

Cited by 32 publications

References 45 publications

Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

Electrochemical and Mechanistic Study of Superoxide Elimination by Mesalazine through Proton-Coupled Electron Transfer

Comparing the Relative Reactivities of Structurally Varied Alcohols toward Electrochemically Generated Superoxide

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