scholarly journals Antioxidant and Antiradical Properties of Some Examples of Flavonoids and Coumarins—Potentiometric Studies

Chemosensors ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 112
Author(s):  
Elena Gerasimova ◽  
Elena Gazizullina ◽  
Ekaterina Radosteva ◽  
Alla Ivanova
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Antioxidant Properties ◽  
Hydrogen Atom Transfer ◽  
Peroxyl Radicals ◽  
Mutual Arrangement ◽  
Hydroxyl Groups ◽  
Metal Chelation ◽  
Electron Transfer Mechanism ◽  
Antiradical Properties

A comprehensive study of a range of flavonoids and coumarins is presented in this article. The work uses an approach that evaluates the activity of these compounds by various mechanisms: the electron transfer (ET), the hydrogen atom transfer (HAT), and the mechanism of metal chelation. The studies were carried out using the methods of the cyclic voltammetry and the potentiometry. The electrochemical behavior of these compounds was studied by the method of cyclic voltammetry; the main types of voltammograms, depending on the oxidation mechanisms, were identified. Various versions of potentiometric sensor systems have been used to detect analytical signal in approaches implemented in ET, HAT and metal chelation mechanisms. The antioxidant capacity was studied by the electron-transfer mechanism. Compounds with antioxidant properties were selected; half-reaction periods for these compounds have been determined. It has been shown that electron-donating and complexing properties directly depend on the mutual arrangement of hydroxyl groups in the molecule. The antiradical ability of the compounds has been studied. It was shown that all studied compounds inhibit peroxyl radicals. Series on the change in antioxidant and antiradical properties of compounds have been compiled. There is no correlation between the results of the study of antioxidant properties obtained using sensory systems that reveal various antioxidant mechanisms. The need to use an integrated approach in the study of antioxidant properties is shown.

scholarly journals Evaluation of the Radical-Scavenging Properties of Various Flavonols in Ethanol Environment: an ab initio Study

2019 ◽  
Vol 92 (3) ◽  
pp. 337-346
Author(s):  
Raluca Pop
Keyword(s):  
Electron Transfer ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Hydroxyl Groups ◽  
Spin Distribution ◽  
Parent Molecule ◽  
Oh Groups ◽  
Fukui Functions ◽  
Reactivity Descriptors

The antioxidant properties of six flavonols -fisetin, galangin, gossipetin, kaempferol, morin and myricetin- have been investigated at HF/6-311G+(d,p) level of theory, using ethanol as solvent. Three known antioxidant mechanisms, namely HAT (hydrogen atom transfer), SET-PT (single electron transfer followed by proton transfer) and SPLET (sequential proton loss electron transfer) have been employed in order to evaluate the radical scavenging abilities of the investigated compounds. Thermodynamic parameters like bond dissociation energy (BDE), proton affinity (PA), electron transfer enthalpy (ETE), ionization potential (IP) and proton dissociation enthalpy (PDE) were calculated and the results were associated with the number and the positions of the hydroxyl groups, the geometry of the parent molecule and of the corresponding radicals, as well as with the electron spin distribution. Also, computations of global reactivity descriptors like HOMO-LUMO gap showed that an increased reactivity is related to the presence of the catechol moiety (gossipetin, myricetin, fisetin). The influence of the catecholic OH groups is also outlined by the HOMO energies, highest electron-donor ability being obtained for gossipetin, the flavonol with two catecholic moieties on rings A and B. According to the HAT mechanism, it has been outlined an enhanced antioxidant character of the 3-OH groups, followed by the hydroxyl groups attached to the phenyl ring B. The calculated values of the condensed Fukui functions, computed for a radical attack, are in good agreement with the above-mentioned results.

Atmospheric formation of the NO3 radical from gas-phase reaction of HNO3 acid with the NH2 radical: proton-coupled electron-transfer versus hydrogen atom transfer mechanisms

2014 ◽  
Vol 16 (36) ◽  
pp. 19437-19445 ◽  
Author(s):  
Josep M. Anglada ◽  
Santiago Olivella ◽  
Albert Solé
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Phase Reaction ◽  
Electron Transfer Mechanism ◽  
Proton Coupled Electron Transfer ◽  
No3 Radical ◽  
Transfer Mechanisms ◽  
Atmospheric Formation

The amidogen radical abstracts the hydrogen from nitric acid through a proton coupled electron transfer mechanism rather than by an hydrogen atom transfer process.

Theoretical insight into the substituent effects on the antioxidant properties of 8-hydroxyquinoline derivatives in gas phase and in polar solvents

2018 ◽  
Vol 96 (5) ◽  
pp. 453-458
Author(s):  
Anes El-Hadj Saïd ◽  
Sidi Mohamed Mekelleche ◽  
Taki-Eddine Ahmed Ardjani
Keyword(s):  
Electron Transfer ◽  
Gas Phase ◽  
Antioxidant Properties ◽  
Substituent Effects ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Antioxidant Power ◽  
Theoretical Insight ◽  
Insight Into

The objective of this work is to perform a theoretical analysis of the antioxidant properties of a series of 8-hydroxyquinolines (8-HQs) to rationalize the available experimental results and to design new potent 8-HQ derivatives. The study was carried out in gas phase and in methanol at the DFT/B3LYP/ 6-311++G(d,p) computational level. The formation of stable ArO• radicals is discussed on the basis of different mechanisms, namely, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and single proton loss electron transfer (SPLET). The obtained results show that the HAT mechanism is, thermodynamically, more favoured in gas phase, whereas the SPLET pathway is more favoured in polar solvents. The calculated thermochemical descriptors allow classification of the antioxidant power of the studied compounds.

Antioxidant Properties of Phenolic Compounds:  H-Atom versus Electron Transfer Mechanism

2004 ◽  
Vol 108 (22) ◽  
pp. 4916-4922 ◽  
Author(s):  
Monica Leopoldini ◽  
Tiziana Marino ◽  
Nino Russo ◽  
Marirosa Toscano
Keyword(s):  
Electron Transfer ◽  
Phenolic Compounds ◽  
Antioxidant Properties ◽  
Transfer Mechanism ◽  
Electron Transfer Mechanism

scholarly journals In-Situ Sensing of Microbial Growth Phases via Two-Terminal Cyclic Voltammetry

2020 ◽  
Author(s):  
Arindam Kushagra ◽  
Diyasa Bazal ◽  
Anup Kumar Pradhan ◽  
Pratyusha Ghosh ◽  
Akshaya Pandey
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Microbial Growth ◽  
Extracellular Polymeric Substances ◽  
Electrochemical Sensors ◽  
Extracellular Electron Transfer ◽  
Growth Phases ◽  
Electron Transfer Mechanism ◽  
Temporal Area ◽  
In Situ Sensing

Microbial growth has been of prime importance to the researchers in health and biotechnology industries. It has been known to be closely associated to the secretion of extracellular polymeric substances that help in the formation of colonies. Inter-microbial communication happens within such colonies by means of extracellular electron transfer mediated by the aforementioned polymeric substances. Conventionally, different phases of microbial growth are monitored with the aid of a traditional UV-Visible spectrophotometer by measuring the optical density of the liquid medium at 280 nm. In this paper, we have developed an alternative novel way to sense different growth phases employing electrochemical means i.e. two-terminal cyclic voltammetry. This cyclic voltammetry relies on the extracellular electron transfer mechanism taking place via the polymeric substances secreted by the microorganisms, measured by the temporal area changes in the current-voltage hysteresis curves in the inoculated nutrient broth. This work paves a new way to detect the biological activity in the medium, which can be directly correlated to the population of microorganisms. It would be of immense interest to scientists and researchers working in the field of microbiology as well as in development of biosensors, electrochemical sensors etc. which would be helpful in absence of traditional spectrophotometers.

Cyclic voltammetry to study kinetics of blast furnace slag and cerium dioxide modified electrode

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arti Mourya ◽  
Sudip K. Sinha ◽  
Bidyut Mazumdar
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Blast Furnace ◽  
Modified Electrode ◽  
Rate Constant ◽  
Blast Furnace Slag ◽  
Cerium Dioxide ◽  
Electron Transfer Mechanism ◽  
General Chemical ◽  
Furnace Slag

Abstract The use of a voltammetric sensor to measure hazardous elements has gotten a lot of coverage. The electrochemical sensor in this study was modified with cerium dioxide (CeO2) and blast furnace slag (BFS), which opens up new possibilities for improving the electrocatalytic properties of the fabricated sensor. In general chemical kinetics or mass transport can restrict the reactions involved in electrochemical detection. The prepared electrodes were tested against potassium ferricyanide, K3Fe(CN)6 solution by cyclic voltammetry. Cyclic voltammetry was used to investigate the chemical reactions involve during redox process. The electron transfer kinetics, chemical rate constant, and diffusion characteristics of reactions can all be extracted using this method. Further this sensor was applied in the detection of lead and copper ions in aqueous solution. The results show that the redox reaction is a one-electron transfer mechanism with high selectivity and sensitivity. The value of transfer coefficient (α) for the electrode reaction was calculated as 0.61. Also the calculated heterogeneous electron transfer rate constant (Ks) of the modified electrode was 2.41.

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