Quantum molecular modeling of quercetin—Simulation of the interaction with the free radical t‐BuOO⋅*

Vasilescu, D.; Girma, R.

doi:10.1002/qua.1801

Cited by 24 publications

(12 citation statements)

References 26 publications

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“…In the case of the flavones luteolin and apigenin, which lack the 3-OH group, the HF optimizations pointed to a nonplanar structure not only for the neutral species but also for the 5-and 7-anions. Our results for quercetin and myricetin essentially match the previous semiempirical [40,41] and ab initio findings [20] though with lesser deviations from planarity than the semiempiricals. In addition, the optimized geometric parameters of quercetin are fairly close to the X-ray crystal structure reported by Jin et al [42]; the main differences are the torsion angle between rings B and C (X-ray:…”

Section: Structuressupporting

confidence: 93%

Toward the prediction of the activity of antioxidants: Experimental and theoretical study of the gas-phase acidities of flavonoids

Martins

Leal

Fernandez

et al. 2004

J. Am. Soc. Mass Spectrom.

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The relative gas-phase acidities were determined for eight flavonoids, applying the kinetic method, by means of electrospray-ion trap mass spectrometry. The experimental acidity order, myricetin > luteolin > quercetin > (+/-)-taxifolin > kaempferol > apigenin > (+)-catechin > (+/-)-naringenin shows good agreement with the order obtained by theoretical calculations at the B3LYP/6-311 + G(2d,2p)//HF/6-31G(d) level. Moreover, these calculations provide the gas-phase acidities of the different OH groups for each flavonoid. The calculated acidity values (Delta(ac)H), corresponding to the most favorable deprotonation, cover a narrow range, 314.8-330.1 kcal/mol, but the experimental method is sensitive enough to differentiate the acidity of the various flavonoids. For all the flavones and the flavanol, catechin, the 4'-hydroxyl group is the most favored deprotonation site whereas for the flavanones studied, taxifolin and naringenin, the most acidic site is the 7-hydroxyl group. On the other hand, the 5-hydroxyl, in flavones and naringenin, and the 3-hydroxyl, in taxifolin and catechin, are always the less acidic positions. The acidity pattern observed for this family of compounds mainly depends on the following structural features: The ortho-catechol group, the 2,3 double bond and the 4-keto group.

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Section: Structuressupporting

confidence: 93%

Toward the prediction of the activity of antioxidants: Experimental and theoretical study of the gas-phase acidities of flavonoids

Martins

Leal

Fernandez

et al. 2004

J. Am. Soc. Mass Spectrom.

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“…Only mechanisms involving direct addition of O 2 to quercetin were investigated. Some previous theoretical studies were devoted to reactivity of quercetin, [18,19] but none especially on the metabolization of O 2 . Since the aim of this work is to answer open questions concerning the oxidation state of the copper atom along the reaction path, we chose the simplest route, that is, to determine whether oxygenolysis is energetically easier when quercetin is oxidized or not.…”

Section: Introductionmentioning

confidence: 99%

Oxygenolysis of Flavonoid Compounds: DFT Description of the Mechanism for Quercetin

et al. 2004

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Flavonoids are naturally occurring phenol derivatives present in substantial amounts in a large variety of plants, fruits and vegetables daily eaten by humans. Most of these compounds exhibit several interesting biological activities, such as antiradical and antioxidant actions. Indeed, by complexation with specific enzymes, flavonoids are notably liable to metabolize molecular dioxygen. On the basis of experimental results describing oxygenolysis of the flavonoid quercetin, activated by the enzyme quercetin 2,3-dioxygenase (2,3-QD),ur attention has focused on the role of metal center in the activation of the substrate quercetin. Thus, in the present study, by means of DFT calculations at the B3LYP/ 6-31(+)G* level on model molecular systems, we describe different mechanisms for dioxygen metabolization by quercetin. Stationary points are described, and energetic and structural analyses along the reaction paths are reported. Our calculations show that the copper cation must act as an oxidant towards the substrate and that the reaction proceeds through a 1,3-cycloaddition.

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“…A new optimization of the geometry was adopted using the semi-empiric method AM1 (Austin Model 1) (Dewar et al, 1985). The choice of the AM1 method was based on the satisfactory results presented on the planning and evaluation for the molecular modeling of antioxidant substances (Cheng et al, 2002;Vasilescu & Girma, 2002). The options selected in the procedure of the geometry optimization, like multiplicity and total charge, were the following: charge 0 and singlet for the closed shell species (fn); charge 0 and doublet for the free radicals (fr); charge 1 and doublet for the cationic species (fc) (Scotti et al, 2005).…”

Section: Methodsmentioning

confidence: 99%

Molecular physicochemical parameters predicting antioxidant activity of Brazilian natural products

Scotti¹,

Scotti²,

Pasqualoto³

et al. 2009

Rev. bras. farmacogn.

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RESUMO: "Parâmetros físico-químicos na predição da atividade antioxidante de produtos naturais brasileiros". Espécies reativas de oxigênio (ROS) são capazes de oxidar proteínas celulares, ácidos nucléicos e lipídios; contribuindo para os processos de envelhecimento celular, mutações genéticas, doenças coronarianas, neoplásicas, degenerativas, dentre outras. Compostos fenólicos neutralizam a reatividade radicalar através da transferência de um elétron da sua estrutura molecular, seguida da abstração de um próton. Este trabalho avaliou a atividade antioxidante de dezessete compostos fenólicos, extraídos de duas plantas da flora nacional (Chimarrhis turbinata e Arrabidea samydoides). Através da modelagem molecular foram obtidos diversos parâmetros, como energias orbitalares, calor de formação das espécies neutras, radicalares e catiônicas, ΔH OX , ΔH f e ClogP; que permitem predizer a atividade e indicar maior poder antioxidante nas moléculas 10 (a a f) para avaliação experimental.Unitermos: Modelagem molecular, compostos fenólicos, atividade antioxidante. ABSTRACT:Reactive oxygen species (ROS) are capable of oxidizing cellular proteins, nucleic acids and lipids, contributing to cellular aging, mutagenesis, carcinogenesis, coronary heart and neurodegenerative diseases. Free radicals-scavenging by phenolic compounds occurs by the transfer of one electron followed by the H-abstraction. In order to evaluate the antioxidant activity of a series of seventeen phenolic compounds extracted from Brazilian flora (Chimarrhis turbinata and Arrabidea samydoides), some physicochemical parameters (heat formation of the neutral, radical, and cationic compounds; orbitals' energies; ClogP; ΔH OX ; and ΔH f ) were calculated. Considering the results from the calculated descriptors, the molecules 10a-f can be classified as having a higher antioxidant activity.

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Quantum molecular modeling of quercetin—Simulation of the interaction with the free radical t‐BuOO^⋅*

Cited by 24 publications

References 26 publications

Toward the prediction of the activity of antioxidants: Experimental and theoretical study of the gas-phase acidities of flavonoids

Toward the prediction of the activity of antioxidants: Experimental and theoretical study of the gas-phase acidities of flavonoids

Oxygenolysis of Flavonoid Compounds: DFT Description of the Mechanism for Quercetin

Molecular physicochemical parameters predicting antioxidant activity of Brazilian natural products

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