scholarly journals Free Radical Scavenging Potency of Dihydroxybenzoic Acids

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Dejan Milenković ◽  
Jelena Đorović ◽  
Svetlana Jeremić ◽  
Jasmina M. Dimitrić Marković ◽  
Edina H. Avdović ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Free Radical ◽  
Density Functional ◽  
Reaction Pathway ◽  
Radical Scavenging ◽  
Theoretical Models ◽  
Hydrogen Atom Transfer ◽  
Free Radical Scavenging ◽  
Thermodynamic Quantities ◽  
Antioxidative Action

In order to evaluate the free radical scavenging potency of dihydroxybenzoic acids (DHBAs) the Density Functional Theory (DFT) was used. The M05-2X/6-311++G(d,p) and B3LYP-D2/6-311++G(d,p) theoretical models were applied. Three possible antioxidant mechanisms were examined: hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms. All of these mechanisms have been studied in nonpolar (benzene and pentylethanoate) and polar solvents (water) using an implicit solvation model (SMD). The following thermodynamic quantities related to these mechanisms were calculated: bond dissociation enthalpy (BDE), ionization potential (IP), and proton affinity (PA). The obtained results indicated the HAT mechanism as the most favourable reaction pathway for antioxidative action of DHBAs in benzene. On the other hand, SPLET is indicated as predominant reaction mechanism in polar solvent. The SET-PT mechanism was not favourable reaction path for antioxidative action in any of the solvents under investigation.

Usnic Acid as a Potential Free Radical Scavenger and its Inhibitory Activity Toward SARS-CoV-2 Proteins

2021 ◽  
Vol 20 (06) ◽  
pp. 655-666
Author(s):  
Jelena Đorović Jovanović ◽  
Nedeljko Manojlović ◽  
Zoran Marković
Keyword(s):  
Free Radical ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Usnic Acid ◽  
Hydrogen Atom Transfer ◽  
Free Radical Scavenging ◽  
Radical Scavenger ◽  
Radical Species ◽  
Free Radical Species ◽  
Antioxidative Action

The antioxidative activity and free radical scavenging potency of usnic acid towards eight selected free radical species are examined. The thermodynamic parameters in the absence of harmful free radicals are used to predict the most favorable mechanism of antioxidative action. The reaction enthalpies are used to define the most probable mechanism of free radical scavenging in the presence of free radical species. The obtained results indicate that the favorable mechanism of antiradical action is dependent both on the polarity of solvents and the nature of free radical species. From the achieved results, it is clear that Sequential Proton Loss Electron Transfer (SPLET) is the most probable for antioxidative action in water and methanol, while competition between SPLET and Hydrogen Atom Transfer (HAT) is presented in benzene. The free radical scavenging of eight free radical species under investigation is possible, and the most believable mechanism of action is SPLET, in all three investigated solvents. Since usnic acid exhibits significant radical scavenging activity that affects the maintenance of redox hemostasis, its inhibitory potency toward COVID-19 targeted proteins molecular docking study is performed. The obtained results indicate that usnic acid has the potential to inhibit the functional proteins of SARS-CoV-2.

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.

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.

scholarly journals Synthesis, crystal structure with free radical scavenging activity and theoretical studies of Schiff bases derived from 1-naphthylamine, 2,6-diisopropylaniline, and substituted benzaldehyde

2021 ◽  
Vol 12 (2) ◽  
pp. 204-215
Author(s):  
Segun Daniel Oladipo ◽  
Tunde Lewis Yusuf ◽  
Sizwe Joshua Zamisa ◽  
Gideon Femi Tolufashe ◽  
Kolawole Ayodapo Olofinsan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Free Radical ◽  
Schiff Bases ◽  
Density Functional ◽  
Radical Scavenging Activity ◽  
Intermolecular Hydrogen Bond ◽  
Radical Scavenging ◽  
Free Radical Scavenging ◽  
Monoclinic Space Group ◽  
Spectroscopic Techniques

Three Schiff bases 1-(4-chlorophenyl)-N-(naphthalen-1-yl)methanimine (1), 1-(4-methoxy phenyl)-N-(naphthalen-1-yl)methanimine (2), and 1-(4-chlorophenyl)-N-(2,6-diisopropyl phenyl)methanimine (3) were synthesized and characterized by elemental analysis, 1H and 13C NMR, FT-IR and UV-Visible spectroscopic techniques. The crystal structure of compound 3 was obtained and it revealed that the compound crystallized in a monoclinic space group P21/n and there exists an intermolecular hydrogen bond in a phenyl-imine form with C-H⋯N. Crystal data for C19H22ClN: a = 7.28280(10) Å, b = 9.94270(10) Å, c = 24.0413(2) Å, β = 97.0120(10)°, V = 1727.83(3) Å3, Z = 4, μ(Mo Kα) = 0.215 mm-1, Dcalc = 1.1526 g/cm3, 14038 reflections measured (12.42° ≤ 2Θ ≤ 52.74°), 3448 unique (Rint = 0.0223, Rsigma = 0.0182) which were used in all calculations. The final R1 was 0.0337 (I≥2u(I)) and wR2 was 0.0927 (all data). The free radical scavenging activities of all three compounds were assayed using DPPH, FRAP, and OH assays. According to results obtained, compound 2 shows effective DPPH- (IC50 = 22.69±0.14 μg/mL), FRAP+ (IC50 = 28.44±0.12 μg/mL), and OH- (IC50 = 27.97±0.16 μg/mL) scavenging activities compared with compounds 1 and 3 but less than standard antioxidant compound Trolox (TRO). Additionally, theoretical calculations for the three complexes were performed by using density functional theory (DFT) calculations at the B3LYP/6-31++G(2d,2p) level in the ground state to obtain an optimized geometrical structure and to perform an electronic, molecular electronic potential surface and natural bond orbital (NBO) analysis. The geometrical calculation obtained was found to be consistent with the experimental geometry. Further analysis was conducted using the in silico technique to predict the drug likeness, molecular and ADME properties of these molecules.

scholarly journals In Vitro and In Silico Antioxidant Activity of Novel Peptides Prepared from Paeonia Ostii ‘Feng Dan’ Hydrolysate

Antioxidants ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 433 ◽  
Author(s):  
Min Wang ◽  
Cong Li ◽  
Haoyu Li ◽  
Zibo Wu ◽  
Bang Chen ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Free Radical ◽  
In Silico ◽  
Density Functional ◽  
Radical Scavenging ◽  
Free Radical Scavenging ◽  
Basis Set ◽  
Superior Performance ◽  
Antioxidant Peptides

Antioxidant peptides derived from natural products have superior performance and broader application prospects. In this study, five novel antioxidant peptides were prepared from Paeonia ostii (P. ostii) seed meal, moreover the bioactive and the relationship between structure and properties of antioxidant peptides were elucidated by quantum chemical calculations. The free radical-scavenging activities were used as indexes to purify and concentrate the antioxidant peptides through five proteases and separation techniques. FSAP (Phe-Ser-Ala-Pro), PVETVR (Pro-Val-Glu-Thr-Val-Arg), QEPLLR (Gln-Glu-Pro-Leu-Leu-Arg), EAAY (Glu-Ala-Ala-Tyr) and VLRPPLS (Val-Leu-Arg-Pro-Pro-Leu-Ser) were identified by nano liquid chromatography–tandem mass spectrometry (LC-MS/MS). In vitro antioxidant activity test, EAAY exhibited the highest 2, 2’-azino-bis (ABTS) and hydroxyl radical-scavenging activity of 98.5% ± 1.1% and 61.9% ± 1.3%, respectively (p < 0.01), at 0.5 mg/mL. In silico calculations were carried out using the density functional theory (DFT) with the B3LYP/6-31G* basis set. According to natural bond orbital (NBO) analysis, the bioactivity of free-radical scavenging of the peptides was presumed. Moreover, the antioxidant peptides demonstrated no obvious cytotoxicity to L929 fibroblast cells. Therefore, the peptides from P. ostii seed by-products might potentially have excellent uses in functional foods, nutraceuticals and pharmacological products.

scholarly journals Antioxidative Action of Ellagic Acid—A Kinetic DFT Study

Antioxidants ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 587 ◽  
Author(s):  
Jelena Tošović ◽  
Urban Bren
Keyword(s):  
Ellagic Acid ◽  
Density Functional ◽  
Molecular Mechanisms ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Kinetic Studies ◽  
Hydrogen Atom Transfer ◽  
Formation Mechanisms ◽  
Electron Transfer Mechanism ◽  
Antioxidative Action

Although one can find numerous studies devoted to the investigation of antioxidative activity of ellagic acid (EA) in the scientific literature, the mechanisms of its action have not yet been fully clarified. Therefore, further kinetic studies are needed to understand its antioxidative capacity completely. This work aims to reveal the underlying molecular mechanisms responsible for the antioxidative action of EA. For this purpose, its reactions with HO• and CCl3OO• radicals were simulated at physiological conditions using the quantum mechanics-based test for overall free-radical scavenging activity. The density functional theory in combination with the conductor-like polarizable continuum solvation model was utilized. With HO• radical EA conforms to the hydrogen atom transfer and radical adduct formation mechanisms, whereas sequential proton loss electron transfer mechanism is responsible for scavenging of CCl3OO• radical. In addition, compared to trolox, EA was found more reactive toward HO•, but less reactive toward CCl3OO•. The calculated rate constants for the reactions of EA with both free radicals are in a very good agreement with the corresponding experimental values.

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