Method For Determination Of Quercetin Research Articles

Development and validation of an HPLC method for determination of quercetin

This study validated a high performance liquid chromatography (HPLC) method for the determination of quercetin (QE) in microemulsion (ME) based gel formulations. The analyses were performed on a C18 column (150x4.6 mm, 5 μm particle size) at room temperature with UV detection at 254 nm. The mobile phase was composed of methanol:water (65:35, v/v, 2% acetic acid) mixture, and flow rate was set to 1 mL/min. The method was validated according to the international guidelines with respect to linearity range, stability, limit of quantitation and detection, precision and accuracy. The method was linear within 5 – 100 μg/mL range with a correlation coefficient of 0.9995. The intra- and inter-assay precisions presented RSD values lower than 2%. The method reported is a fast and reliable HPLC method useful for QE determination in ME based gel formulations.

Development and Validation of HPLC Method for Determination of Quercetin in Hydrogel Transdermal Patches Loaded with Red Onion Peel Extract

In the earlier published article, the Table 4 under Results and Discussion section was omitted. The correction has been made as stated below:

Development and Validation of HPLC Method for Determination of Quercetin in Hydrogel Transdermal Patches Loaded with Red Onion Peel Extract

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A validated high‑performance thin-layer chromatography method for the simultaneous determination of quercetin and gallic acid in Annona reticulata L.

A validated high‑performance thin-layer chromatography method for the simultaneous determination of quercetin and gallic acid in Annona reticulata L.

A Sensitive and Low-cost Analytical Method for the Electrochemical Determination of Quercetin, Based on 1-Ethylpyridinium Bromide/Carbon Paste Composite Electrode

We report a simple, sensitive and low-cost electrochemical procedure for the quantification of quercetin (QCT), a flavonoid and an antioxidant, based on 1-ethylpyridinium bromide modified carbon paste electrode. A 1-ethylpyridinium bromide/carbon paste composite electrode was used. The cyclic voltammogram of QCT showed two oxidation peaks at +0.575 V (vs Ag/AgCl/3M KCl) and +0.865 V (vs Ag/AgCl/3M KCl), and a reduction peak at +0.371 V (vs Ag/AgCl/3M KCl) in HCl/KCl solution at pH 1. Differential pulse voltammetry (DPV) analysis in HCl/KCl at pH 1 showed three well-defined oxidation peaks while a single peak was recorded in phosphate buffer at pH 3. The peak currents of QCT significantly increased at the 1-ethylpyridinium bromide modified electrode in comparison with those recorded at the bare carbon paste electrode. This allowed the use of adsorptive stripping voltammetry to develop a simple and sensitive electroanalytical method for the determination of QCT. Key experimental parameters such as pH of the supporting electrolyte, the preconcentration time, the electrolysis potential, electrode composition, QCT concentration and interferents were investigated. The current response was found to be directly proportional to the concentration of QCT in the range from 2.48 x 10-7 M to 7.43 x 10-6 M, leading to a detection limit of 4.48 x 10-8 M. The developed analytical method was successfully applied to the determination of QCT in human urine samples.

A Sensitive and Low-cost Analytical Method for the Electrochemical Determination of Quercetin, Based on 1-Ethylpyridinium Bromide/Carbon Paste Composite Electrode

We report a simple, sensitive and low-cost electrochemical procedure for the quantification of quercetin (QCT), a flavonoid and an antioxidant, based on 1-ethylpyridinium bromide modified carbon paste electrode. A 1-ethylpyridinium bromide/carbon paste composite electrode was used. The cyclic voltammogram of QCT showed two oxidation peaks at +0.575 V ( vs Ag/AgCl/3M KCl) and +0.865 V ( vs Ag/AgCl/3M KCl), and a reduction peak at +0.371 V ( vs Ag/AgCl/3M KCl) in HCl/KCl solution at pH 1. Differential pulse voltammetry (DPV) analysis in HCl/KCl at pH 1 showed three well-defined oxidation peaks while a single peak was recorded in phosphate buffer at pH 3. The peak currents of QCT significantly increased at the 1-ethylpyridinium bromide modified electrode in comparison with those recorded at the bare carbon paste electrode. This allowed the use of adsorptive stripping voltammetry to develop a simple and sensitive electroanalytical method for the determination of QCT. Key experimental parameters such as pH of the supporting electrolyte, the preconcentration time, the electrolysis potential, electrode composition, QCT concentration and interferents were investigated. The current response was found to be directly proportional to the concentration of QCT in the range from 2.48 x 10 -7 M to 7.43 x 10 -6 M, leading to a detection limit of 4.48 x 10 -8 M. The developed analytical method was successfully applied to the determination of QCT in human urine samples.

A developed and validated high-performance thin-layer chromatographic method for the quantitative determination of quercetin inSatyrium nepalensetubers

Satyrium nepalense D. Don (Orchidaceae) is a reservoir of numerous chemical compounds such as flavonoids, glycosides, and unsaturated sterols/triterpenes. Thin-layer chromatography (TLC) and qualitative tests confirm the presence of quercetin in S. nepalense tubers — this is why we must pay attention to its chemistry. A simple, sensitive, and accurate method developed with a normal-phase high-performance thin-layer chromatography (HPTLC) has been optimised for the separation, identification, and quantitative estimation of quercetin in the methanol extract of S. nepalense tubers. Chromatography was performed by using aluminum TLC plates precoated with silica gel 60 F254 using toluene-ethyl acetate-formic acid (7:5:1, v/v) as the solvent system at 25 ± 2°C. Linear ascending development was carried out in a saturated twin-trough glass chamber. Densitometric determinations were performed in reflectance-absorbance mode by using a deuterium lamp (D2) for excitation at 366 nm and a K400 filter in order to measur...

Development and validation of a new RP-HPLC method for determination of quercetin in green tea

Green tea (Camellia sinensis) contains quercetin as a bioactive compound. Quercetin has anti-inflammatory and anticancer effects. The aim of this paper was to develop and validate an RP-HPLC method for determination of quercetin in green tea simpler and faster than other available methods. RP-HPLC analysis was performed by isocratic elution with a flow rate of 1.0 mL/min. Pure methanol was used as a mobile phase, while the quantification was effected at 370 nm. The separation was performed at 35°C using a C18 column (4.6 × 250 mm, 5 μm). The results showed that the peak area response is linear within the concentration range of 10–70 μg/mL (r = 0.9986). The values of LOD and LOQ were 1.2 and 4 μg/mL, respectively. For the intra-day and intra-instrument reproducibility, RSD were in the range of 0.05–0.84% and 0.89–1.55%, respectively. The results of accuracy for the different concentrations of quercetin (40, 50 and 60 μg/mL) were 101.3, 98.4, and 98.2%. The developed and validated method was successfully applied to the determination of quercetin in green tea extract.

An on-line method for pressurized hot water extraction and enzymatic hydrolysis of quercetin glucosides from onions

A novel environmentally sound continuous-flow hot water extraction and enzymatic hydrolysis method for determination of quercetin in onion raw materials was successfully constructed using a stepwise optimization approach. In the first step, enzymatic hydrolysis of quercetin-3,4′-diglucoside to quercetin was optimized using a three level central composite design considering temperature (75–95°C), pH (3–6) and volume concentration of ethanol (5–15%). The enzyme used was a thermostable β-glucosidase variant (termed TnBgl1A_N221S/P342L) covalently immobilized on either of two acrylic support-materials (Eupergit® C 250L or monolithic cryogel). Optimal reaction conditions were irrespective of support 84°C, 5% ethanol and pH 5.5, and at these conditions, no significant loss of enzyme activity was observed during 72h of use. In a second step, hot water extractions from chopped yellow onions, run at the optimal temperature for hydrolysis, were optimized in a two level design with respect to pH (2.6 and 5.5), ethanol concentration (0 and 5%) and flow rate (1 and 3mLmin−1) Obtained results showed that the total quercetin extraction yield was 1.7 times higher using a flow rate of 3mLmin−1 (extraction time 90min), compared to a flow rate of 1mLmin−1 (extraction time 240min). Presence of 5% ethanol was favorable for the extraction yield, while a further decrease in pH was not, not even for the extraction step alone. Finally, the complete continuous flow method (84°C, 5% ethanol, pH 5.5, 3mLmin−1) was used to extract quercetin from yellow, red and shallot onions and resulted in higher or similar yield (e.g. 8.4±0.7μmolg−1 fresh weight yellow onion) compared to a conventional batch extraction method using methanol as extraction solvent.

Development and Validation of a New RP-HPLC Method for Determination of Quercetin in Green Tea

Development and Validation of a New RP-HPLC Method for Determination of Quercetin in Green Tea

Hot Electron Induced Cathodic Electrochemiluminescence at Disposable Screen Printed Carbon Electrodes

AbstractHot electron induced cathodic electrochemiluminescence (ECL) was observed at screen printed carbon electrodes (SPCEs) during pulse polarization. The thin insulating film resulted from the printing inks was found to be suitable for generating hot electrons, which can further be converted to hydrated electrons and induce the subsequent luminescence. Compared with disposable Al/Al2O3 electrode, SPCEs show more stable and reproducible ECL in a wider pH range without background emission. A sensitive ECL method for determination of quercetin is proposed. The detection limit is 8.0×10−10 mol L−1(S/N=3), which is two magnitudes lower than that of common ECL method.

Validation of an isocratic LC method for determination of quercetin and methylquercetin in topical nanoemulsions

The aim of this study was to validate an isocratic LC method for the quantification of either quercetin (Q) or methylquercetin (MQ) incorporated in topical nanoemulsions. The analyses were performed at room temperature on a reversed-phase C 18 column using a mobile phase composed of methanol/water (70:30, v/v) and trifluoracetic acid 0.1% at 0.8 mL min −1. The detection was carried out on a UV detector at 368 or 354 nm for Q and MQ, respectively. The linearity, in the range of 0.15–1.5 μg/mL, presented a determination coefficient ( r 2) higher than 0.99, calculated by the least square method for both flavonoids. No interferences from the excipients (egg-lecithin or octyldodecanol) were detected. The R.S.D. values for intra- and inter-day precision experiments were lower than 2% for both flavonoids. The recovery ranged from 98.9% to 103.46% for Q and from 98.9% to 102.92% for MQ.

Identification of quercetin glucuronides in human plasma by high-performance liquid chromatography–tandem mass spectrometry

After intake of food or herbal medicinal products containing quercetin glycosides, the systemic availability of the genuine glycoside, as well as the systemic occurrence of the aglycone or conjugates of this polyphenol has been a matter of dispute. Consequently, we designed this study to develop a reliable method for determination of quercetin and its metabolites. Following consumption of fried onions five different glucuronides of quercetin could be identified in human plasma samples by means of HPLC–UV–MS/MS. Selective determination of the target compounds was achieved by simultaneous UV (254 nm) and MS/MS detection with selected reaction monitoring experiments using positive mode electrospray ionisation. In contrast, neither the free flavonol nor the genuine glycoside could be detected in plasma. Identification of the quercetin glucuronides detected in vivo was confirmed by comparison with authentic reference compounds synthesised enzymatically using glucuronyl transferase from rabbit liver.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC ASSAY FOR THE DETERMINATION OF QUERCETIN IN PLASMA

A sensitive, reproducible, simple, and accurate high performance liquid chromatographic (HPLC) method for the quantitative determination of quercetin in plasma has been developed and validated. Sample preparation involves simultaneous precipitation of plasma proteins and extraction of quercetin and kaempferol (the internal standard) from 0.1 mL plasma. The separation was performed in a stainless steel Ultrasphere-ODS column with a mobile phase consisted of a mixture of 30% acetonitrile and 70% of 5% acetic acid in HPLC water. The mobile phase was pumped at a flow rate of 1.5 mL/min and the effluent was monitored at 375 nm. The retention times for the drug and the internal standard were found to be 3.5 and 6.2 minutes, respectively. Peak-area ratios of the drug to the internal standard were used for quantitation of quercetin in plasma samples. The limit of detection of drug in plasma was found to be 0.06 μg/mL. The intra-day coefficient of variation (CV) ranged from 4.35% to 9.47%, and the inter-day CV ranged from 1.77% to 6.38% at three different concentrations. Mean absolute recoveries ranged from 96.52% to 101.19% and the relative recoveries ranged from 92.64% to 111.03% at three different concentrations. Preliminary stability tests showed that quercetin is stable for at least 8 weeks in plasma after freezing at -20°C. The method was applied for the determination of the pharmacokinetic parameters of quercetin after intravenous administration to three rats.

A selective spectrophotometric method for determination of quercetin in the presence of other flavonoids

A simple, rapid and highly selective method for determination of quercetin in the presence of other flavonoids was developed. The method is based on the oxidation reaction of quercetin in neutral aqueous solution with N-bromosuccinimide (NBS) in the presence of phenol to give a violet chromogen measurable at 510 nm. Beer's law was valid within a concentration range of 2.5–30 μg/ml with a good correlation coefficient ( r = 0.9990). All variables were studied to optimize the reaction conditions. The method is highly selective for quercetin. Other investigated flavonoids do not interfere. Mixtures of flavonoids were also analysed through native UV measurements of absorbance readings at 370 nm and then at 510 mn after adopting the proposed procedure. The method could also be utilized for the quantitative determination of quercetin in some plant extracts. Moreover, the proposed procedure could be considered as a good tool to follow the hydrolysis of quercetin glycosides.

Sensitive Fluorometric Method for Determination of Quercetin in Plasma or Urine

Abstract A fluorometric method is described for determining quercetin, a flavonoid compound, in plasma and urine. It is based on the formation of the highly fluorescent quercetin-tetraphenyldiboroxide complex. The excitation wavelength used is 445 nm, the emission wavelength 500 nm.