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.

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

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.

scholarly journals Antioxidant Properties of Camphene-Based Thiosemicarbazones: Experimental and Theoretical Evaluation

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1192
Author(s):  
Lijuan Yang ◽  
Haochuang Liu ◽  
Dasha Xia ◽  
Shifa Wang
Keyword(s):  
Density Functional ◽  
Peroxyl Radical ◽  
Biological Activities ◽  
Radical Scavenging Activity ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Theoretical Data ◽  
Hydrogen Atom Transfer ◽  
Theoretical Evaluation ◽  
Wide Range

The thiosemicarbazone derivatives have a wide range of biological activities, such as antioxidant activity. In this study, the antiradical activities of six camphene-based thiosemicarbazones (TSC-1~6) were investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and peroxyl radical scavenging capacity (PSC) assays, respectively, and the results reveal that TSC1~6 exhibited good abilities for scavenging free radicals in a dose-dependent way. Compound TSC-2 exhibited the best effect of scavenging DPPH radical, with the lowest EC50 (0.208 ± 0.004 mol/mol DPPH) as well as the highest bimolecular rate constant Kb (4218 M−1 s−1), which is 1.18-fold higher than that of Trolox. Meanwhile, TSC-2 also obtained the lowest EC50 (1.27 µmol of Trolox equiv/µmol) of scavenging peroxyl radical. Furthermore, the density functional theory (DFT) calculation was carried out to further explain the experimental results by calculating several molecular descriptors associated with radical scavenging activity. These theoretical data suggested that the electron-donating effect of the diethylamino group in TSC-2 leads to the enhancement of the scavenging activities and the studied compounds may prefer to undergo the hydrogen atom transfer process.

scholarly journals Antioxidant and UV-radiation absorption activity of aaptamine derivatives – Potential application for natural organic sunscreens

2021 ◽  
Author(s):  
Thi Le Anh Nguyen ◽  
Thi Hoai Nam Doan ◽  
Dinh Hieu Truong ◽  
Nguyen Thi Ai Nhung ◽  
Duong Tuan Quang ◽  
...  
Keyword(s):  
Density Functional ◽  
Antioxidant Activities ◽  
Radical Scavenging Activity ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Radiation Absorption ◽  
Chelating Activity ◽  
Radical Adduct ◽  
Potential Applications

Antioxidant and UV absorption activities of three marine product originated - aaptamine derivatives including piperidine[3,2-b]demethyl(oxy)aaptamine (<b>C1</b>), 9-amino-2-ethoxy-8-methoxy-3H-benzo[de][1,6]naphthyridine-3-one (<b>C2</b>), and 2-(sec-butyl)-7,8-dimethoxybenzo[de]imidazo[4,5,1-ij][1,6]-naphthyridin-10(9H)-one (<b>C3</b>) were theoretically studied by density functional theory (DFT). Direct antioxidant activities of C1–C3 were firstly evaluated via their intrinsic thermochemical properties and radical scavenging activity of the potential antioxidants with 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 (kapp, 7.13x10<sup>6</sup> M-1 s-1) while RAF is more dominant with C2 (k<sub>app</sub>, 1.40x10<sup>5</sup> M-1 s-1) and C3 (kapp, 2.90x10<sup>5</sup> M-1 s-1). Antioxidant activity of aaptamine derivatives can be classified as <b>C1 </b>> <b>C3 </b>> <b>C2</b>. Indirect antioxidant properties based on Cu(I) and Cu(II) ions chelating activity were also investigated in aqueous phase. All three studied compounds show spontaneous and favorable Cu(I) ion chelating activity with DG0 being -15.4, -13.7, and -15.7 kcal.mol-1, whereas DG0 for Cu(II) chelation are -10.4, -10.8, and -2.2 kcal.mol-1 for C1, C2 and C3, respectively. In addition, all compounds show UVA and UVB absorption; in which the excitations are determined mostly 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>

scholarly journals DFT study of the radical scavenging activity of isoxanthohumol, humulones (α-acids) and iso-α-acids from beer

2021 ◽  
Author(s):  
Ilija N. Cvijetić ◽  
Miljan Bigović ◽  
Petar Ristivojević ◽  
Maja Vitorović-Todorović ◽  
Mire Zloh ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Density Functional ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Natural Antioxidants ◽  
Dft Method ◽  
Hydrogen Atom Transfer ◽  
Antioxidant Mechanism ◽  
Intramolecular Hydrogen ◽  
Cis And Trans

Abstract Humulones and iso-humulones are potent natural antioxidants found in beer. In this study, density functional theory (DFT) method was applied for elucidating the structure-antioxidant activity relationship and molecular mechanism of antioxidant activity of eight bioactive humulones previously identified in different beer samples: isoxanthohumol, ( R )- and ( S )-adhumulone, cis - and trans -iso-adhumulone, cis - and trans -iso-n-humulone, and desdimetyhyl-octahydro-iso-cohumulone. The calculated bond dissociation enthalpies (BDEs) suggest that desdimethyl-octahydro-iso-cohumulone was the most potent compound with BDEs 5.1 and 23.9 kJ/mol lower compared to the values for resveratrol in gas phase and water, respectively. The enolic –OH is the most reactive site for hydrogen atom transfer (HAT). The presence of β-keto group with respect to enolic –OH diminishes the HAT potency via the formation of a strong intramolecular hydrogen bond. Another common antioxidant mechanism, single electron transfer followed by proton transfer (SET-PT), is only feasible for isoxanthohumol. The results of this study indicate a strong correlation between the increased antioxidant activity of beer products and the higher content of reduced iso-α-acids.

COMBINED EXPERIMENTAL AND COMPUTATIONAL STUDY OF THE RADICAL SCAVENGING ACTIVITY OF LUTEOLIN

2013 ◽  
Vol 12 (05) ◽  
pp. 1350021 ◽  
Author(s):  
ABDULLAH G. AL-SEHEMI ◽  
AHMAD IRFAN ◽  
SALHA MANA ALJUBIRI ◽  
KAMEL HUSSEIN SHAKER
Keyword(s):  
Density Functional Theory ◽  
Absorption Spectra ◽  
Density Functional ◽  
Computational Study ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
2D Nmr ◽  
Hydrogen Atom Transfer ◽  
Functional Theory ◽  
Polarized Continuum Model

The luteolin has been extracted from Euphorbia schimperiana then 1H NMR, 13C NMR and 2D NMR spectra were measured. The ground-state geometries have been computed by using density functional theory (DFT) at B3LYP/6-31G* and M06/6-31++G** level of theories. The time dependent density functional theory (TD-DFT) has been applied to compute the absorption spectra with and without solvent. The absorption spectra have been computed in methanol to check the effect of solvent using the polarized continuum model (PCM). On the basis of bond dissociation enthalpy (BDE) and the adiabatic ionization potential (IP), we have explained the antioxidant activity of luteolin and its rotamer/positional isomer. Two mechanisms have been explained for the radical scavenging processes, i.e. hydrogen atom transfer and one-electron transfer.

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.

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