scholarly journals COMPUTATIONAL STUDY OF MOLECULAR STRUCTURES AND ANTIOXIDANT MECHANISM OF OVOTHIOLS

2018 ◽  
Vol 54 (2C) ◽  
pp. 328
Author(s):  
Tien Dung Le
Keyword(s):  
Chemical Potential ◽  
Computational Study ◽  
Hydrogen Atom Transfer ◽  
Molecular Structures ◽  
Chemical Hardness ◽  
Antioxidant Mechanism ◽  
Dissociation Enthalpy ◽  
Proton Dissociation ◽  
Vertical Ionization Energy ◽  
Antioxidant Mechanisms

In this paper, the molecular structure and antioxidant activity of ovothiols (OSH) have beenstudied by using four DFT functionals, namely B3LYP, B3PW91, X3LYP, M06 with the basisset of 6-311++G(2df,2p). Two major antioxidant mechanisms, namely, hydrogen atom transfer(HAT) and stepwise electron transfer-proton transfer (SET-PT) have been investigated andapplied on three optimized conformations of ovothiols. Bond dissociation enthalpy (BDE),vertical ionization energy (IE), proton dissociation enthalpy (PDE), chemical potential (μ),chemical hardness (η) and global electrophilicity (ω), have been calculated and discussed in thegas phase.

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 Study on the chemical potential of apigenin, luteolin, quercetin, and myricetin using the molecular modeling

2021 ◽  
Vol 44 (1) ◽  
pp. 63-66
Author(s):  
Steluta Gosav ◽  
Adriana Hodorogea ◽  
Dan Maftei
Keyword(s):  
Gas Phase ◽  
Chemical Potential ◽  
Chemical Compounds ◽  
Molecular Structures ◽  
Basis Set ◽  
Chemical Hardness ◽  
Equilibrium Geometry ◽  
Hybrid Functional ◽  
Electrophilicity Index ◽  
Quantum Molecular Descriptors

In the present paper, the chemical potential of four flavonoids i.e. apigenin, luteolin, quercetin, and myricetin, of interest in the pharmaceutical industry was investigated using molecular modelling. The equilibrium geometry of molecular structures was calculated in the gas phase and ground state by using B3LYP hybrid functional in conjunction with a 6-311G(d,p) basis set. In order to assess the chemical potential of investigated flavonoids, the main quantum molecular descriptors, such as the dipole moment, the energy of the highest/lowest occupied/unoccupied molecular orbital, the gap energy, the electronegativity, the chemical hardness/softness, and the electrophilicity index have been computed. Also, the influence of the hydroxylation degree of chemical compounds on the chemical potential is discussed.

scholarly journals Computational Study of Geometry, Solvation Free Energy, Dipole Moment, Polarizability, Hyperpolarizability and Molecular Properties of 2-Methylimidazole

2016 ◽  
Vol 21 (2) ◽  
pp. 89
Author(s):  
Mohammad Firoz Khan ◽  
Ridwan Bin Rashid ◽  
Shahidul M. Islam ◽  
Mohammad A. Rashid
Keyword(s):  
Free Energy ◽  
Dipole Moment ◽  
Chemical Potential ◽  
Computational Study ◽  
Solvation Free Energy ◽  
Molecular Properties ◽  
Chemical Hardness ◽  
Electrophilicity Index ◽  
Reactivity Descriptors ◽  
Solvent Systems

Ab initio calculations were carried out to study the geometry, solvation free energy, dipole moment, molecular electrostatic potential (MESP), Mulliken and Natural charge distribution, polarizability, hyperpolarizability, Natural Bond Orbital (NBO) energetic and different molecular properties like global reactivity descriptors (chemical hardness, softness, chemical potential, electronegativity, electrophilicity index) of 2-methylimidazole. B3LYP/6-31G(d,p) level of theory was used to optimize the structure both in the gas phase and in solution. The solvation free energy, dipole moment and molecular properties were calculated by applying the Solvation Model on Density (SMD) in four solvent systems, namely water, dimethylsulfoxide (DMSO), n-octanol and chloroform. The computed bond distances, bond angles and dihedral angles of 2-methylimidazole agreed reasonably well with the experimental data except for C(2)-N(1), C(4)-C(5) and N(1)-H(7) bond lengths and N(1)-C(5)-C(4) bond angle. The solvation free energy, dipole moment, polarizability, first order hyperpolarizability, chemical potential, electronegativity and electrophilicity index of 2-methylimidazole increased on going from non-polar to polar solvents. Chemical hardness also increased with increasing polarity of the solvent and the opposite relation was found in the case of softness. These results provide better understanding of the stability and reactivity of 2-methylimidazole in different solvent systems.  

scholarly journals A Deep Insight in the Antioxidant Property of Carnosic Acid: From Computational Study to Experimental Analysis

Foods ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2279
Author(s):  
Jing Wei ◽  
Qian Liang ◽  
Yuxin Guo ◽  
Weimin Zhang ◽  
Long Wu
Keyword(s):  
Thermal Oxidation ◽  
Computational Study ◽  
Oxidation Stability ◽  
Hydrogen Atom Transfer ◽  
Phenolic Hydroxyl ◽  
Carnosic Acid ◽  
Hydroxyl Groups ◽  
Dissociation Enthalpy ◽  
Rancimat Method ◽  
Thermal Oxidation Stability

Since the deep cause for the anti-oxidation of carnosic acid (CA) against oleic acid (OA) remains unclear, we focused on exploring the CA inhibition mechanism via a combined experimental and computational study. Atomic charge, total molecular energy, phenolic hydroxyl bond dissociation enthalpy (BDE), the highest occupied molecular orbital (HOMO), and the lowest unoccupied orbital (LUMO) energy were first discussed by the B3LYP/6-31G (d,p) level, a density functional method. A one-step hydrogen atom transfer (HAT) was proposed for the anti-oxidation of CA towards OA, and the Rancimat method was carried out for analyzing the thermal oxidation stability. The results indicate that the two phenolic hydroxyl groups located at C7(O15) and C8(O18) of CA exert the highest activity, and the chemical reaction heat is minimal when HAT occurs. Consequently, the activity of C7(O15) (303.27 kJ/mol) is slightly lower than that of C8(O18) (295.63 kJ/mol), while the dissociation enthalpy of phenol hydroxyl groups is much lower than those of α-CH2 bond of OA (C8, 353.92 kJ/mol; C11, 353.72 kJ/mol). Rancimat method and non-isothermal differential scanning calorimetry (DSC) demonstrate that CA outcompetes tertiary butylhydroquinone (TBHQ), a synthetic food grade antioxidant, both in prolonging the oxidation induction period and reducing the reaction rate of OA. The Ea (apparent activation energies of reaction) of OA, TBHQ + OA, and CA + OA were 50.59, 57.32 and 66.29 kJ/mol, revealing that CA could improve the Ea and thermal oxidation stability of OA.

THEORETICAL STUDY OF THE SUBSTITUENT EFFECTS ON THE REACTION ENTHALPIES OF THE ANTIOXIDANT MECHANISMS OF STOBADINE DERIVATIVES IN THE GAS-PHASE AND WATER

2013 ◽  
Vol 12 (02) ◽  
pp. 1250116 ◽  
Author(s):  
MEYSAM NAJAFI ◽  
MOHAMMAD NAJAFI ◽  
HOUSHANG NAJAFI
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects ◽  
Partial Charge ◽  
Action Mechanisms ◽  
Dissociation Enthalpy ◽  
Proton Dissociation ◽  
Highest Occupied Molecular Orbital ◽  
Phase Water ◽  
Antioxidant Mechanisms

In this paper the reaction enthalpies of three antioxidant action mechanisms, HAT, SET–PT, and SPLET, for mono-substituted Stobadines were calculated in gas-phase and water. Results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. Results show that IP and BDE values can be successfully correlated with the indolic N–H bond length after electron abstraction, R(N–H+•), and the partial charge on the indolyl radical nitrogen atom, q( N ). Furthermore, calculated IP and PA values for mono-substituted Stobadines show linear dependence on the energy of the highest occupied molecular orbital (E HOMO ) of studied molecules in the two environments. SPLET represents the thermodynamically preferred mechanism in water.

scholarly journals Computational Study of Geometry, IR Spectrum and Molecular Properties of Acetanilide

2016 ◽  
Vol 19 (2) ◽  
pp. 170-178 ◽  
Author(s):  
Mohammad Firoz Khan ◽  
Rahatullah Razan ◽  
Ridwan Bin Rashid ◽  
Faiza Tahia ◽  
Mohammad A Rashid
Keyword(s):  
Ir Spectrum ◽  
Chemical Potential ◽  
Computational Study ◽  
Pharmaceutical Journal ◽  
Molecular Properties ◽  
Basis Sets ◽  
Mulliken Charge ◽  
Chemical Hardness ◽  
Reactivity Descriptors ◽  
Ir Frequencies

In this paper an effort has made to conduct and repot the computational study of geometry, IR spectrum and different molecular properties like Molecular Electrostatic Potential (MESP), Mulliken Charge Distribution, Global Reactivity Descriptors such as chemical hardness, softness, chemical potential, electronegativity, and electrophilicity index of acetanilide. All calculations were performed on Hartee-Fock (HF), Becke and 3-parameter, Lee-Yang-Parr (B3LYP) with 6-31G(d) and 6-31+G(d,p) basis sets. The calculated geometries (bond length, bond angle and dihedral angle) were in a good agreement with the experimental data for both level of theories and basis sets. In case of IR frequencies the scaled calculated frequencies agreed reasonably well with the experimental results.Bangladesh Pharmaceutical Journal 19(2): 170-178, 2016

scholarly journals Photoprotective Properties of Eumelanin: Computational Insights into the Photophysics of a Catechol:Quinone Heterodimer Model System

Photochem ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 26-37
Author(s):  
Victoria C. Frederick ◽  
Thomas A. Ashy ◽  
Barbara Marchetti ◽  
Michael N. R. Ashfold ◽  
Tolga N. V. Karsili
Keyword(s):  
Ground State ◽  
Sandwich Structure ◽  
Computational Study ◽  
Minimum Energy ◽  
Carbonyl Oxygen ◽  
Model System ◽  
Molecular Structures ◽  
Uv Damage ◽  
Chromosomal Dna ◽  
Relevant Model

Melanins are skin-centered molecular structures that block harmful UV radiation from the sun and help protect chromosomal DNA from UV damage. Understanding the photodynamics of the chromophores that make up eumelanin is therefore paramount. This manuscript presents a multi-reference computational study of the mechanisms responsible for the experimentally observed photostability of a melanin-relevant model heterodimer comprising a catechol (C)–benzoquinone (Q) pair. The present results validate a recently proposed photoinduced intermolecular transfer of an H atom from an OH moiety of C to a carbonyl-oxygen atom of the Q. Photoexcitation of the ground state C:Q heterodimer (which has a π-stacked “sandwich” structure) results in population of a locally excited ππ* state (on Q), which develops increasing charge-transfer (biradical) character as it evolves to a “hinged” minimum energy geometry and drives proton transfer (i.e., net H atom transfer) from C to Q. The study provides further insights into excited state decay mechanisms that could contribute to the photostability afforded by the bulk polymeric structure of eumelanin.

scholarly journals Antioxidant activity of Spathodea campanulata (Bignoneaceae) extracts

2012 ◽  
Vol 14 (2) ◽  
pp. 287-292 ◽  
Author(s):  
S.C Heim ◽  
F.A Guarnier ◽  
D.T Ferreira ◽  
R Braz-Filho ◽  
R Cecchini ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Complex Formation ◽  
Mechanism Of Action ◽  
Iron Complex ◽  
Bark Extract ◽  
Flower Extract ◽  
Antioxidant Mechanism ◽  
Activity Loss ◽  
Ethanol Extracts ◽  
Antioxidant Mechanisms

Spathodea campanulata is used in traditional medicine in Africa as diuretic and anti-inflammatory. Although few studies have reported the mechanism of antioxidant action, this study evidenced the antioxidant activity of S. campanulata bark and flower extracts and their possible mechanism of action. Ethanol extracts of S. campanulata bark and flowers showed antioxidant activity on lipid peroxidation of liver microsome induced by Fe3+-ascorbic acid. Bark extract was 5 times more efficient than flower extract. The antioxidant activity of flower extract, previously complexed with increasing concentrations of Fe3+ (20 - 100 μM) which resulted in antioxidant activity loss, was shown to be related to iron complex formation. In contrast, the antioxidant activity of bark extract was not inhibited by the previous incubation with Fe3+, although complexation was demonstrated by spectral analysis of the solution. These results suggest an antioxidant mechanism other than Fe3+ complex formation. Therefore, the antioxidant mechanisms of S. campanulata flower and bark extracts are distinct from each other, reflecting the extract heterogeneous composition and the mechanism of action.

scholarly journals On local aromaticity of selected model aza-[n]circulenes (n = 6, 7, 8 and 9): Density functional theoretical study

2019 ◽  
Vol 12 (1) ◽  
pp. 70-81
Author(s):  
Denisa Cagardová ◽  
Vladimír Lukeš ◽  
Ján Matúška ◽  
Peter Poliak
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Molecular Structures ◽  
Functional Theory ◽  
Structure Of Molecules ◽  
Planar Molecules ◽  
P Type ◽  
Structural Indices ◽  
Lowest Unoccupied Molecular Orbitals ◽  
Local Aromaticity

Abstract A computational study using density functional theory is reported for selected model aza[n]circulenes (n = 6, 7, 8 and 9) and their derivatives consisting of pyrrole and benzene units. Local aromaticity of central rings was discussed and analyzed using theoretical structural indices. Depending on their molecular structures, energies of the highest occupied and lowest unoccupied molecular orbitals change from –5.23 eV to –4.08 eV and from –1.97 eV to –0.41 eV, respectively. Based on B3LYP calculated optimal geometries, electronic structure of molecules and their charge transport properties resulted in the suggestion of three planar molecules containing three or four pyrrole units as potential candidates for p-type semiconductors. Hole drift mobilities for ideal stacked dimers of these potential semiconductors were calculated and they range from 0.94 cm2·V−1·s−1 to 7.33 cm2·V−1·s−1.

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