scholarly journals Substituent Effects on the Radical Scavenging Activity of Isoflavonoid

2019 ◽  
Vol 20 (2) ◽  
pp. 397 ◽  
Author(s):  
Yan-Zhen Zheng ◽  
Geng Deng ◽  
Rui Guo ◽  
Da-Fu Chen ◽  
Zhong-Min Fu
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Antioxidative Activity ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Substituent Effects ◽  
Hydrogen Atom Transfer ◽  
Electronic Effects ◽  
Antioxidative Properties ◽  
Electronic Effects Of Substituents

Understanding the role of substituents is of great importance for the preparation of novel phenolic compounds with enhanced antioxidative properties. In this work, the antioxidative activity of isoflavonoid derivatives with different substituents placed at the C2 position was determined by density functional theory (DFT) calculations. The bond dissociation enthalpy (BDE), ionization potential (IP), and proton affinity (PA) related to hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were calculated. The strongest antioxidative group of isoflavonoid is not altered by the substituents. Excellent correlations were found between the BDE/IP/PA and Hammett sigma constants. Equations obtained from linear regression can be useful in the selection of suitable candidates for the synthesis of novel isoflavonoids derivatives with enhanced antioxidative properties. In the gas and benzene phases, the electron-donating substituents would enhance the antioxidative activity of isoflavonoids via weakening the BDE of 4′−OH. In water phase, they will reduce the antioxidative by strengthening the PA of 7−OH. Contrary results occur for the electron-withdrawing groups. In addition, the electronic effects of substituents on the BDE/IP/PA have also been analyzed.

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.

scholarly journals Radical-Scavenging and UV-Radiation Absorption Activities of Aaptamine Derivatives: DFT and TD-DFT Studies

2021 ◽  
Author(s):  
Thi Hoai Nam Doan ◽  
Thi Le Anh Nguyen ◽  
Nguyen Thi Ai Nhung ◽  
Duong Tuan Quang ◽  
Duy Quang Dao
Keyword(s):  
Density Functional ◽  
Antioxidant Activities ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Radiation Absorption ◽  
Functional Theory ◽  
Radical Adduct ◽  
Td Dft ◽  
Potential Applications

Antioxidant and UV absorption activities of three aaptamine derivatives including piperidine[3,2-b]demethyl(oxy)aaptamine (C1), 9-amino-2-ethoxy-8-methoxy-3H-benzo[de][1,6]naphthyridine-3-one (C2), and 2-(sec-butyl)-7,8-dimethoxybenzo[de]imidazo[4,5,1-ij][1,6]-naphthyridin-10(9H)-one (C3) were theoretically studied by density functional theory (DFT). Optimized geometries of C1C3 and theirs intrinsic thermochemical properties such as bond dissociation energy, proton affinity, and ionization potential were calculated at DFT/M05-2X/6-311++G(d,p) level of theory in vacuo and in water. The results show that C1C3 exhibited similar potent antioxidant activities, which are comparable to well-known antioxidants such as Trolox or cembrene. The radical scavenging activity of the antioxidants were then investigated by evaluation the Gibbs free energy (ΔrG0) of the reaction between C1C3 and the HOO●/HO● radicals via four mechanisms, including: hydrogen atom transfer (HAT), single electron transfer (SET), proton loss (PL) and radical adduct formation (RAF). Kinetic calculation reveals that HOO● scavenging in water is occurred via HAT mechanism with C1@C19 while RAF is more dominant with C2 and C3. Antioxidant activity of aaptamine derivatives can be classified as C1 > C3 > C2. In addition, all compounds are active in UV-Vis absorption; the excitations of which are determined as π-π* transition. Overall, the results suggest the potential applications of the aaptamines in pharmaceutics and cosmetics, i.e. as sunscreen and antioxidant ingredient<br>

Density Functional Theory Calculations of the Radical Scavenging Activity of Alkannin Derivatives

2012 ◽  
Vol 189 ◽  
pp. 225-231
Author(s):  
Xiang Peng Guo ◽  
Rui Fa Jin
Keyword(s):  
Density Functional ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Density Functional Theory Calculations ◽  
Hydrogen Atom Transfer ◽  
Scavenging Activity ◽  
Functional Theory ◽  
Hydrogen Bond Formation ◽  
Structural And Electronic Properties ◽  
The One

The structural and electronic properties of alkannin and its derivatives and their radicals were investigated at density functional level. It turned out that the presence of the dihydroxy functionality increases the radical stability through hydrogen bond formation. The hydrogen atom transfer for alkannin derivatives is difficult to occur compared with zero compound phenol. However, alkannin derivatives appear to be good candidates for the one-electron-transfer, particularly for alkannin derivatives with –OCOCH=CH(CH3)2 and –OCOCH2CH(CH3)2 groups. It suggests that 1–7 are expected to be the promising candidates for radical scavenging activity compounds because The ionization potential (IP) values of 1–7 are lower than that of the zero compound phenol.

scholarly journals Scavenging of hydroxyl radical by kinsenoside originated from anoectochilus roxburghii: A DFT approach

2020 ◽  
pp. 72-76
Author(s):  
Nguyen Minh Thong Nguyen
Keyword(s):  
Hydroxyl Radical ◽  
Density Functional ◽  
Energy Surface ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Single Electron Transfer ◽  
Functional Theory ◽  
Anoectochilus Roxburghii ◽  
Radical Scavenging Properties

- A density functional theory (DFT) study on the hydroxyl radical scavenging properties of Kinsenoside originated from Anoectochilus roxburghii is presented. Two mechanisms, single electron transfer (SET) and hydrogen atom transfer (HAT) are considered. The thermochemical results demonstrate that the SET mechanism is not plausible to occur. With respect to the HAT, the interaction of OH• radical with Kinsenoside is also studied in detail by establishing potential energy surface (PES). This result strongly confirms that the C8H bond decides the radical scavenging activity of Kinsenoside with activation Gibbs free energy (∆G≠) and rate constants (k) of 1.1 kcal/mol and 5.9×10-8 cm3/molecules, respectively

scholarly journals The Substituent Effect on the Radical Scavenging Activity of Apigenin

Molecules ◽  
2018 ◽  
Vol 23 (8) ◽  
pp. 1989 ◽  
Author(s):  
Yan-Zhen Zheng ◽  
Da-Fu Chen ◽  
Geng Deng ◽  
Rui Guo
Keyword(s):  
Density Functional ◽  
Antioxidative Activity ◽  
Radical Scavenging Activity ◽  
Resonance Effect ◽  
Radical Scavenging ◽  
Free Radical Scavengers ◽  
Polar Phase ◽  
Natural Foods ◽  
Electron Donating Groups ◽  
The Relationship

Flavonoids widely found in natural foods are excellent free radical scavengers. The relationship between the substituent and antioxidative activity of flavonoids has not yet been completely elucidated. In this work, the antioxidative activity of apigenin derivatives with different substituents at the C3 position was determined by density functional theory (DFT) calculations. The bond dissociation enthalpy (BDE), ionization potential (IP), and proton affinity (PA) were calculated. Donator acceptor map (DAM) analysis illustrated that the studied compounds are worse electron acceptors than F and also are not better electron donors than Na. The strongest antioxidative group of apigenin derivatives was the same as apigenin. Excellent correlations were found between the BDE/IP/PA and Hammett sigma constants. Therefore, Hammett sigma constants can be used to predict the antioxidative activity of substituted apigenin and to design new antioxidants based on flavonoids. In non-polar phases, the antioxidative activity of apigenin was increased by the electron-withdrawing groups, while it was reduced by the electron-donating groups. Contrary results occurred in the polar phase. The electronic effect of the substituents on BDE(4′-OH), BDE(5-OH), PA(4′-OH), and IP is mainly controlled by the resonance effect, while that on BDE(7-OH), PA(5-OH), and PA(7-OH) is governed by the field/inductive effect.

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.

THERMODYNAMICS OF THE ANTIOXIDANT ACTIVITY OF HUMULONES AND OTHER ANTIOXIDANTS FROM BEER – A MOLECULAR MODELING APPROACH

2021 ◽  
Author(s):  
Ilija Cvijetić ◽  
◽  
Miljan Bigović ◽  
Petar Ristivojević ◽  
Maja Vitorović-Todorović ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Free Radicals ◽  
Gas Phase ◽  
Density Functional ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Structural Basis ◽  
Recent Experimental Study ◽  
Cis And Trans

Recent experimental study identified eight potent antioxidants in German beers, including isoxanthohumol, (R)- and (S)-adhumulone, cis– and trans-iso-adhumulone, cis– and trans-iso- n-humulone, and desdimetyhyl-octahydro-iso-cohumulone. To provide insights into the structural basis of their radical scavenging activity, we calculated the thermodynamic feasibility of two common antioxidant mechanisms, hydrogen atom transfer (HAT) and single electron transfer followed by proton transfer (SET-PT), using the density functional theory (DFT) with B3LYP/6-311g++(2d,2p) method in the gas phase and implicit solvation model of water. The calculated bond dissociation enthalpies (BDEs) and ionization potential (IP) of all compounds were compared with the corresponding values for resveratrol, a highly potent antioxidant found in red wine. The fully reduced humulone isomer, desdimetyhyl-octahydro-iso-cohumulone, could scavenge free radicals via HAT as revealed by BDEs 5.1 and 23.9 kJ/mol lower than the values for resveratrol in gas phase and water, respectively. Furthermore, the enolic –OH group was identified as the pharmacophoric hotspot for the interaction of humulones with the reactive free radicals. The HAT potency of this group is significantly reduced through the formation of strong intramolecular hydrogen bond (IHB) with the β-keto group. Moreover, the SET-PT mechanism was thermodynamically favorable for isoxanthohumol. These results strongly suggest higher antioxidant activity of beers with the increased content of the reduced forms of humulones and their isomers.

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 Computational Study of Ortho-Substituent Effects on Antioxidant Activities of Phenolic Dendritic Antioxidants

Antioxidants ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 189 ◽  
Author(s):  
Choon Young Lee ◽  
Ajit Sharma ◽  
Julius Semenya ◽  
Charles Anamoah ◽  
Kelli N. Chapman ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Electron Transfer ◽  
Antioxidant Activities ◽  
Computational Study ◽  
Radical Scavenging ◽  
Substituent Effects ◽  
Phenolic Antioxidants ◽  
Electronic Effects ◽  
Total Enthalpy ◽  
Structure Activity

Antioxidants are an important component of our ability to combat free radicals, an excess of which leads to oxidative stress that is related to aging and numerous human diseases. Oxidative damage also shortens the shelf-life of foods and other commodities. Understanding the structure–activity relationship of antioxidants and their mechanisms of action is important for designing more potent antioxidants for potential use as therapeutic agents as well as preservatives. We report the first computational study on the electronic effects of ortho-substituents in dendritic tri-phenolic antioxidants, comprising a common phenol moiety and two other phenol units with electron-donating or electron-withdrawing substituents. Among the three proposed antioxidant mechanisms, sequential proton loss electron transfer (SPLET) was found to be the preferred mechanism in methanol for the dendritic antioxidants based on calculations using Gaussian 16. We then computed the total enthalpy values by cumulatively running SPLET for all three rings to estimate electronic effects of substituents on overall antioxidant activity of each dendritic antioxidant and establish their structure–activity relationships. Our results show that the electron-donating o-OCH3 group has a beneficial effect while the electron-withdrawing o-NO2 group has a negative effect on the antioxidant activity of the dendritic antioxidant. The o-Br and o-Cl groups did not show any appreciable effects. These results indicate that electron-donating groups such as o-methoxy are useful for designing potent dendritic antioxidants while the nitro and halogens do not add value to the radical scavenging antioxidant activity. We also found that the half-maximal inhibitory concentration (IC50) values of 2,2-diphenyl-1-picrylhydrazyl (DPPH) better correlate with the second step (electron transfer enthalpy, ETE) than the first step (proton affinity, PA) of the SPLET mechanism, implying that ETE is the better measure for estimating overall radical scavenging antioxidant activities.

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