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.

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 Radical Scavenging Activity of Puerarin: A Theoretical Study

Antioxidants ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 590 ◽  
Author(s):  
Huakang Zhou ◽  
Xiangzhou Li ◽  
Yaxuan Shang ◽  
Kai Chen
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Theoretical Study ◽  
Wide Spectrum ◽  
Radical Scavenging Activity ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Scavenging Activity ◽  
Dissociation Enthalpy

Puerarin is a C-glycoside of daidzein, one of the major bioactive ingredients isolated from the root of Pueraria lobata, which has a wide spectrum of pharmacological effects. Although puerarin is well-known for its effective antioxidant activity, there is seldom a systematic theoretical study on its radical scavenging activity. Herein, the free radical scavenging ability of puerarin was investigated systematically by density functional theory (DFT) calculations. The reaction activity was compared with daidzein as well. Three reaction pathways: hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were discussed and compared by thermodynamic parameters such as bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE). The reaction kinetics of puerarin with special radicals •OH and •OOH were also studied. The results obtained may be of great significance for better understanding the relationship between the antioxidant properties and structural design of puerarin, as well as other antioxidants.

DFT study of free radical scavenging activity of erodiol

2013 ◽  
Vol 67 (11) ◽  
Author(s):  
Zoran Marković ◽  
Jelena Đorović ◽  
Milan Dekić ◽  
Milanka Radulović ◽  
Svetlana Marković ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Free Radical Scavenging ◽  
Single Electron Transfer ◽  
Transfer Energy ◽  
Dissociation Enthalpy ◽  
Proton Dissociation ◽  
Transfer Mechanisms

AbstractAntioxidant activity of erodiol was examined at the M05-2X/6-311+G(d,p) level of theory in the gas and aqueous phases. The structure and energy of radicals and anions of the most stable erodiol rotamer were analyzed. To estimate antioxidant potential of erodiol, different molecular properties were examined: bond dissociation enthalpy, proton affinity together with electron transfer energy, and ionization potential followed by proton dissociation enthalpy. It was found that hydrogen atom transfer is the prevailing mechanism of erodiol behavior in gas; whereas single electron transfer followed by proton transfer and sequential proton loss electron transfer mechanisms represent the thermodynamically preferred reaction paths in water.

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.

scholarly journals Molecular Characterization, Antioxidant and Protein Solubility-Related Properties of Polyphenolic Compounds from Walnut (Juglans regia)

2016 ◽  
Vol 11 (5) ◽  
pp. 1934578X1601100 ◽  
Author(s):  
Diana Labuckas ◽  
Damián Maestri ◽  
Alicia Lamarque
Keyword(s):  
Phenolic Compounds ◽  
Molecular Characterization ◽  
Juglans Regia ◽  
Protein Solubility ◽  
Radical Scavenging ◽  
Analytical Techniques ◽  
Hydrogen Atom Transfer ◽  
Polyphenolic Compounds ◽  
Oh Groups ◽  
Ionization Behavior

Aqueous ethanol extraction of partially defatted walnut flours provides a simple and reliable method to obtain extracts with high content of polyphenolic compounds. These were characterized by means of HPLC-ESI-MS/MS analytical techniques and molecular parameters. Considering the whole set of polyphenolic compounds identified, a high average number of phenolic-OH groups was found. Although these represent potential hydrogen-atom transfer sites, which are associated with high free-radical scavenging capacity, results show that such a property could be strongly limited by the low lipophilicity of polyphenols affecting the accessibility of these molecules to lipid substrates. Variations in pH values were found to change the ionization behavior of phenolic compounds. These changes, however, had minor effects on walnut protein solubility-related properties. The results obtained in this study highlight the importance of molecular characterization of walnut phenolic compounds in order to assess better their bioactive properties.

scholarly journals The Antioxidant and Antiproliferative Activities of 1,2,3-Triazolyl-L-Ascorbic Acid Derivatives

2019 ◽  
Vol 20 (19) ◽  
pp. 4735 ◽  
Author(s):  
Anja Harej ◽  
Andrijana Meščić Macan ◽  
Višnja Stepanić ◽  
Marko Klobučar ◽  
Krešimir Pavelić ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Breast Adenocarcinoma ◽  
Scavenging Activity ◽  
Activity Data ◽  
Oh Groups ◽  
Mcf 7

The novel 4-substituted 1,2,3-triazole L-ascorbic acid (L-ASA) conjugates with hydroxyethylene spacer as well as their conformationally restricted 4,5-unsaturated analogues were synthesized as potential antioxidant and antiproliferative agents. An evaluation of the antioxidant activity of novel compounds showed that the majority of the 4,5-unsaturated L-ASA derivatives showed a better antioxidant activity compared to their saturated counterparts. m-Hydroxyphenyl (7j), p-pentylphenyl (7k) and 2-hydroxyethyl (7q) substituted 4,5-unsaturated 1,2,3-triazole L-ASA derivatives exhibited very efficient and rapid (within 5 min) 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging activity (7j, 7k: IC50 = 0.06 mM; 7q: IC50 = 0.07 mM). In vitro scavenging activity data were supported by in silico quantum-chemical modelling. Thermodynamic parameters for hydrogen-atom transfer and electron-transfer radical scavenging pathways of anions deprotonated at C2-OH or C3-OH groups of L-ASA fragments were calculated. The structure activity analysis (SAR) through principal component analysis indicated radical scavenging activity by the participation of OH group with favorable reaction parameters: the C3-OH group of saturated C4-C5(OH) derivatives and the C2-OH group of their unsaturated C4=C5 analogues. The antiproliferative evaluation showed that p-bromophenyl (4e: IC50 = 6.72 μM) and p-pentylphenyl-substituted 1,2,3-triazole L-ASA conjugate (4k: IC50 = 26.91 μM) had a selective cytotoxic effect on breast adenocarcinoma MCF-7 cells. Moreover, compound 4e did not inhibit the growth of foreskin fibroblasts (IC50 > 100 μM). In MCF-7 cells treated with 4e, a significant increase of hydroxylated hypoxia-inducible transcription factor 1 alpha (HIF-1α) expression and decreased expression of nitric oxide synthase 2 (NOS2) were observed, suggesting the involvement of 4e in the HIF-1α signaling pathway for its strong growth-inhibition effect on MCF-7 cells.

scholarly journals Gallic Acid and Quercetin as Intelligent and Active Ingredients in Poly(vinyl alcohol) Films for Food Packaging

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1999 ◽  
Author(s):  
Francesca Luzi ◽  
Elisa Pannucci ◽  
Luca Santi ◽  
José Maria Kenny ◽  
Luigi Torre ◽  
...  
Keyword(s):  
Gallic Acid ◽  
Vinyl Alcohol ◽  
Food Packaging ◽  
Radical Scavenging Activity ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Casting Process ◽  
Poly Vinyl Alcohol ◽  
Hydroxyl Groups ◽  
Active Ingredients

Gallic acid (GA) and quercetin (QC) were used as active ingredients in poly(vinyl alcohol) (PVA) film formulations obtained by solvent casting process. The effect of two different percentages (5 and 10 % wt.) on morphological behavior, thermal stability, optical, mechanical, and release properties of PVA were investigated, while migration with food stimulants and antioxidant properties were tested taking into account the final application as food packaging systems. The results showed how different dispersability in PVA water solutions gave different results in term of deformability (mean value of ε PVA/5GA = 280% and ε PVA/5QC = 255%, with 190% for neat PVA), comparable values for antioxidant activity at the high contents (Radical Scavenging Activity, RSA(%) PVA/10GA = 95 and RSA(%) PVA/10QC = 91) and different coloring attitude of the polymeric films. It was proved that GA, even if it represents the best antioxidant ingredient to be used with PVA and can be easily dispersed in water, it gives more rigid films in comparison to QC, that indeed was more efficient in tuning the deformability of the PVA films, due the presence of sole hydroxyl groups carrying agent. The deviation of the film coloring towards greenish tones for GA films and redness for QC films after 7 and within 21 days in the simulated conditions confirmed the possibility of using easy processable PVA films as active and intelligent films in food packaging.

Influence of the geometric isomers on the radical scavenging properties of 3,5-dicaffeoylquinic acid: A DFT study in vacuo and in solution

2016 ◽  
Vol 15 (06) ◽  
pp. 1650052 ◽  
Author(s):  
Mpho M. Makola ◽  
Ntakadzeni E. Madala ◽  
Ian A. Dubery ◽  
Paul A. Steenkamp ◽  
Mwadham. M. Kabanda
Keyword(s):  
Antioxidant Activity ◽  
Trans Isomer ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Acid Group ◽  
Hydrogen Atom Transfer ◽  
Food Sources ◽  
Geometrical Isomers ◽  
Dicaffeoylquinic Acid ◽  
Radical Scavenging Properties

3,5-Dicaffeoylquinic acid (diCQA) is a part of the chlorogenic acid group of compounds, largely isolated from food sources and possessing potent antioxidant activity. Only the trans–trans isomer exists in nature, however, abiotic stresses, such as UV-radiation, give rise to cis isomers. There have been no reports on the antioxidant activity of the cis isomers. The current study, performed using the B3LYP/6-311[Formula: see text]G(d,p) method, is aimed at investigating and comparing the antioxidant properties of the geometrical isomers of 3,5-diCQA. The study is conducted by checking the molecules’ ability for two main radical scavenging mechanisms, hydrogen atom transfer (HAT) and electron transfer (ET). A separate DPPH assay experimental study performed in this study shows that all the geometrical isomers are potent radical scavengers. The lowest O[Formula: see text]H bond dissociation enthalpy value (70.599 kcal/mol) corresponds to the trans–trans isomer and is comparable to that of gallic acid, a commercially available antioxidant. The lowest ionization potential value corresponds to the cis–cis isomer (149.54[Formula: see text]kcal/mol), indicating that it is best antioxidant, in terms of ET mechanism.

scholarly journals Free Radical Scavenging Activity of Dihydrocaffeic Acid: A Quantum Chemical Approach

2021 ◽  
Vol 33 (4) ◽  
pp. 937-944
Author(s):  
K. Senthilkumar ◽  
S.S. Naina Mohammed ◽  
S. Kalaiselvan
Keyword(s):  
Electron Transfer ◽  
Quantum Chemical ◽  
Density Functional ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Basis Set ◽  
Published Data ◽  
Chemical Calculation ◽  
Neutral Radical ◽  
Donor And Acceptor

Based on density functional theory (DFT), to investigate relationships between the antioxidant activity and structure of dihydrocaffeic acid, quantum chemical calculation is used. The optimized structures of the neutral, radical and ionic forms have been carried out by DFT-B3LYP method with the 6-311G(d,p) basis set. Reaction enthalpies related with the hydrogen atom transfer (HAT), single electron transfer proton transfer (SET-PT) and sequential proton loss and electron transfer (SPLET) were calculated in gas and water phase. The HOMO-LUMO energy gap, electron affinity, electronegativity, ionization energy, hardness, chemical potential, global softness and global electrophilicity were calculated by using the same level of theory. Surfaces with a molecular electrostatic potential (MEP) were studied to determine the reactive sites of dihydrocaffeic acid. The difference in energy between the donor and acceptor as well as the stabilization energy was determined through the natural bond orbital (NBO) analysis. The Fukui index (FI) based on electron density was employed to predict reaction sites. Reaction enthalpies are compared with previously published data for phenol and 3,4-dihydroxycinnamic acid.

CHLOROGENIC ACID – APPLICATION OF CONTEMPORARY DENSITY FUNCTIONALS TO A SINGLE MOLECULE

2021 ◽  
Author(s):  
Svetlana Marković ◽  
◽  
Jelena Tošović ◽  
Keyword(s):  
Electron Transfer ◽  
Chlorogenic Acid ◽  
Single Molecule ◽  
Reaction Pathway ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Density Functionals ◽  
Perfect Agreement ◽  
Stable Conformation

Although chlorogenic acid (5-O-caffeoylquinic acid, 5CQA) is a dietary phenol known for its pharmacological and nutritional properties, its structural features and mechanisms of oxidative action have not been completely elucidated. Clarification of the 5CQA structure was conducted by comparing the experimental and simulated IR, Raman, 1H-NMR, 13C-NMR, and UV spectra. For this purpose, a comprehensive conformational analysis of 5CQA was performed to reveal its most stable conformations in the gas-state and solution. Excellent agreement between all experimental and simulated spectra indicates correct arrangement of the atoms in the 5CQA molecule. In addition, the most stable conformation in solution coincides with that predicted with sophisticated NMR experiments. The quantum mechanics–based test for overall free-radical scavenging activity was applied for the investigation of antioxidative capacity of 5CQA relative to trolox (6-hydroxy-2,5,7,8- tetramethylchroman-2-carboxylic acid, Tx) as a reference compound. Hydrogen atom transfer (HAT), radical adduct formation (RAF), sequential proton loss electron transfer (SPLET), and single electron transfer – proton transfer (SET-PT) reactions of 5CQA and Tx with HO· and CH3OO· radicals were examined in benzene, pentyl ethanoate, and basic aqueous solutions. In non-polar solvents 5CQA reacts with HO· via HAT and RAF mechanisms, whereas HAT is the only reaction pathway with CH3OO·. At physiological conditions 5CQA exists in the form of monoanion and dianion. Both anionic forms undergo only HAT mechanism with CH3OO·. With HO·, the anions conform to the HAT, RAF, SPLET, and SET-PT mechanisms. Because all reactions of dianion are diffusion controlled, its contribution to scavenging HO· is comparable to that of more abundant monoanion. The calculated rate constant for overall reaction of 5CQA with HO· is in perfect agreement with the corresponding experimental value. The order of reactivity toward selected free radicals is the same in nonpolar and polar solutions: in comparison to Tx, 5CQA is more reactive toward HO·, but less reactive toward CH3OO·. Very good agreement between the experimental and calculated results confirms the ability of contemporary density functionals to quantify subtle physico-chemical interactions.

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