Quercetin In Presence Research Articles

Potential Implications of Quercetin and its Derivatives in Cardioprotection.

Quercetin (QCT) is a natural polyphenolic compound enriched in human food, mainly in vegetables, fruits and berries. QCT and its main derivatives, such as rhamnetin, rutin, hyperoside, etc., have been documented to possess many beneficial effects in the human body including their positive effects in the cardiovascular system. However, clinical implications of QCT and its derivatives are still rare. In the current paper we provide a complex picture of the most recent knowledge on the effects of QCT and its derivatives in different types of cardiac injury, mainly in ischemia-reperfusion (I/R) injury of the heart, but also in other pathologies such as anthracycline-induced cardiotoxicity or oxidative stress-induced cardiac injury, documented in in vitro and ex vivo, as well as in in vivo experimental models of cardiac injury. Moreover, we focus on cardiac effects of QCT in presence of metabolic comorbidities in addition to cardiovascular disease (CVD). Finally, we provide a short summary of clinical studies focused on cardiac effects of QCT. In general, it seems that QCT and its metabolites exert strong cardioprotective effects in a wide range of experimental models of cardiac injury, likely via their antioxidant, anti-inflammatory and molecular pathways-modulating properties; however, ageing and presence of lifestyle-related comorbidities may confound their beneficial effects in heart disease. On the other hand, due to very limited number of clinical trials focused on cardiac effects of QCT and its derivatives, clinical data are inconclusive. Thus, additional well-designed human studies including a high enough number of patients testing different concentrations of QCT are needed to reveal real therapeutic potential of QCT in CVD. Finally, several negative or controversial effects of QCT in the heart have been reported, and this should be also taken into consideration in QCT-based approaches aimed to treat CVD in humans.

Investigation of interactions between quercetin and Tween 80 through electrolyte induced thermodynamic approach

The research work represents the thermodynamic studies of well known flavonoid quercetin in presence of non-ionic surfactant Tween 80. The studies were performed in hydro-ethanolic solvent system (30% v/v ethanol) at five different temperatures (20–40 °C with difference of 5 °C) in order to analyze the changes in thermodynamic properties with respect to temperature change. As Tween 80 is non-ionic surfactant, 1% sodium chloride solution was added as an electrolyte to ensure the flow of electrons. The conductance studies for the flavonoid-surfactant system were carried out and the data thus obtained was utilized to calculate various thermodynamic parameters i.e. standard enthalpy change (ΔHom), standard entropy change (ΔSom) and standard Gibbs free energy change (ΔGom) of micellization. Overall, the effects of quercetin on micellization process of Tween 80 at different temperatures and hydro-ethanolic solvent have been reported.

Insight on nano-platinum-catalyzed dehydrogenation of quercetin in presence of peroxide

Quercetin (Qu), a noted polyphenolic flavonol molecule, exhibits remarkable antioxidant properties against bioenzymes like peroxidase and tyrosinase. However, it was found that under pH = 3.5–5.5 and room temperature, Qu cannot reduce hydrogen peroxide (HP) which is a well-perceived reactive oxygen species (ROS) responsible for oxidative stress. We found that in presence of noble-metal nano-particles, such redox interactions can be accomplished. We thus synthesized homogenous PVP-coated nano-platinum particles (PNP) to catalyze the oxidation of Qu by HP. On reaction, Qu is oxidized by HP to ortho-quinone (QQ) following the first-order kinetics. The observed rate constant, ko, gradually increases and tends to saturate with increasing [HP]T where T represents the analytical concentrations of the reactant. The saturation kinetics indicates that the activities of PNP resemble to that of bioenzymes and similarly, the nano-particles host the reactants on its active surface during the redox interactions. The estimated value of the kcat reveals that the extent of catalysis of even 10−10 M PNP is nearly comparable with the rate constants of oxidation of Qu in presence of enzymes like horseradish peroxidase and tyrosinase.

Phase Solubility Study of Quercetin in Presence of Cyclodextrins and Hydrophilic Polymers.

Phase Solubility Study of Quercetin in Presence of Cyclodextrins and Hydrophilic Polymers.

Determination of quercetin in the presence of tannic acid in soft drinks based on carbon nanotubes modified electrode using chemometric approaches

In the present study, determination of quercetin (QU) was studied in the presence of unexpected electroactive interference (tannic acid, TA) using electrochemical and chemometric methods. At first, the oxidation peak current of QU was optimized in the presence of TA by multivariate optimization strategy. The analysis was performed at the surface of a multi-walled carbon nanotubes modified carbon paste electrode (MWCNTs/CPE). Central composite design (CCD) and response surface methodology (RSM) were used to evaluate the effects of the four variables on the determination of QU in the presence of TA. After modification, determination of QU was investigated in the presence of TA by differential pulse voltammetry (DPV). But the two components showed intense overlapping voltammetric peaks. Therefore, it was impossible to analyze the two analytes by DPV technique. For overcoming the problem chemometric methods were assisted with voltammetric techniques. Multivariate curve resolution with alternating least squares (MCR-ALS) was applied for resolving of these voltammograms. Then, limit of detection (LOD) for QU at the present of TA was obtained 1.96 nM. The results indicated that MWCNTs/CPE could be employed for the determination of QU in presence of TA in soft drinks with satisfactory results.

Effect of pH, Time and Temperature on Forced Degradation Studies of Quercetin in Presence of Polymers

Effect of pH, Time and Temperature on Forced Degradation Studies of Quercetin in Presence of Polymers

Electrochemical behavior of kaempferol and its determination in presence of quercetin employing multi-walled carbon nanotube modified carbon paste electrode

The electrochemical behavior of kaempferol was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV) at plane and multiwalled carbon nanotubes modified carbon paste electrode (MWCNTs/CPE). Kaempferol produces an anodic peak at MWCNTs modified CPE with a quasi-reversible nature in phosphate buffer of pH 7.73. The oxidized species of kaempferol was found to be stable (Ipa/Ipc ≈1) over scan rates of 100∼600 mV−1. The same electrode was also found to catalyze the electrode oxidation of quercetin in presence of kaempferol under similar conditions which enabled the simultaneous determination of kaempferol and quercetin. Linearity of peak currents (Ip) vs. concentrations of kaempferol and quercetin was found in the range of 6.72 × 10−9 M to 40.34 × 10−9 M with a detection limit of 2.90 × 10−9 M for kaempferol and 13.0 × 10−9 M to 50.9 × 10−9 M with a detection limit of 3.5 × 10−9 M for quercetin using fast and sensitive SWV. The developed method has been applied for the quantitative analysis of kaempferol in corms and petals of Indian traditional medicine saffron (Crocus sativus) using a phosphate buffer of pH 7.73 and the average percent recoveries obtained are 99.84 and 99.26, respectively.

Electrochemical behavior of kaempferol and its determination in presence of quercetin employing multi-walled carbon nanotube modified carbon paste electrode

The electrochemical behavior of kaempferol was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV) at plane and multiwalled carbon nanotubes modified carbon paste electrode (MWCNTs/CPE). Kaempferol produces an anodic peak at MWCNTs modified CPE with a quasi-reversible nature in phosphate buffer of pH 7.73. The oxidized species of kaempferol was found to be stable (Ipa/Ipc ≈ 1) over scan rates of 100–600 mV−1. The same electrode was also found to catalyze the electrode oxidation of quercetin in presence of kaempferol under similar conditions which enabled the simultaneous determination of kaempferol and quercetin. Linearity of peak currents (Ip) vs. concentrations of kaempferol and quercetin was found in the range of 6.72 × 10−9 M to 40.34 × 10−9 M with a detection limit of 2.90 × 10−9 M for kaempferol and 13.0 × 10−9 M to 50.9 × 10−9 M with a detection limit of 3.5 × 10−9 M for quercetin using fast and sensitive SWV. The developed method has been applied for the quantitative analysis of kaempferol in corms and petals of Indian traditional medicine saffron (Crocus sativus) using a phosphate buffer of pH 7.73 and the average percent recoveries obtained are 99.84 and 99.26, respectively.

A cupin domain-containing protein with a quercetinase activity (VdQase) regulates Verticillium dahliae's pathogenicity and contributes to counteracting host defenses.

We previously identified rutin as part of potato root responses to its pathogen Verticillium dahliae. Rutin was directly toxic to the pathogen at doses greater than 160 μM, a threshold below which many V. dahliae pathogenicity-related genes were up-regulated. We identified and characterized a cupin domain-containing protein (VdQase) with a dioxygenase activity and a potential role in V. dahliae-potato interactions. The pathogenicity of VdQase knock-out mutants generated through Agrobacterium tumefasciens-mediated transformation was significantly reduced on susceptible potato cultivar Kennebec compared to wild type isolates. Fluorescence microscopy revealed a higher accumulation of flavonols in the stems of infected potatoes and a higher concentration of rutin in the leaves in response to the VdQase mutants as compared to wild type isolates. This, along with the HPLC characterization of high residual and non-utilized quercetin in presence of the knockout mutants, indicates the involvement of VdQase in the catabolism of quercetin and possibly other flavonols in planta. Quantification of Salicylic and Jasmonic Acids (SA, JA) in response to the mutants vs. wild type isolates revealed involvement of VdQase in the interference with signaling, suggesting a role in pathogenicity. It is hypothesized that the by-product of dioxygenation 2-protocatechuoylphloroglucinolcarboxylic acid, after dissociating into phloroglucinol and protocatechuoyl moieties, becomes a starting point for benzoic acid and SA, thereby interfering with the JA pathway and affecting the interaction outcome. These events may be key factors for V. dahliae in countering potato defenses and becoming notorious in the rhizosphere.

Optical Spectroscopy Study of the Interaction Between Quercetin and Human Serum Albumin

Medical Physics Division, Biophysics Department, Collegium Medicum of Nicolaus Copernicus University Jagiello«ska 13, 85-067 Bydgoszcz, Poland Optical methods are very useful for the study on behavior of molecules in albumin-containing solutions. The interaction between quercetin (QUE) and human serum albumin (HSA) under physiological conditions was investigated by the methods of UV-Vis absorption and uorescence spectroscopy. Fluorescence data show that enhancing of quercetin uorescence in the presence of HSA is the result of formation of the HSA-QUE complex. On the basis of uorescence data, the binding a nity constant of quercetin to HSA is determined. In this paper we have attempted to perform a kinetic study of the oxidation of quercetin in presence of human serum albumin by absorption spectroscopy. It has been shown that quercetin easily oxidizes at pH 7.4. The addition of HSA to quercetin solution induces changes in the absorption spectrum. In the human serum albumin solution, the time of quercetin oxidation is longer than in the case of quercetin diluted in phosphate bu ered saline. Human albumin also contributes to stabilization of quercetin. These results suggest that HSA prevents degradation of quercetin in blood. DOI: 10.12693/APhysPolA.125.A-57

Non-ionic micellar solubilization — spectrofluorimetric determination of trace of germanium(IV) with quercetin in real samples

A spectrofluorometric method is described for the determination of germanium(IV) based on its complexation reaction with quercetin in presence of Brij-35. The fluorescence is monitored at 552nm with excitation at 432nm. The pH, quercetin and Brij-35 concentrations were optimized simultaneously using the response surface methodology from sequential experimental three-variable Doehlert designs. Interferences in this determination have been studied. The detection limit is 7.4ngml−1 and the linear range is between 7.4 and 150ngml−1. The method has been applied to the determination of germanium in a drug and in wholemeal oats.