Simultaneous determination of quercetin, kaempferol and isorhamnetin accumulated human breast cancer cells, by high-performance liquid chromatography

Analytical Methods for the Determination of Quercetin and Quercetin Glycosides in Pharmaceuticals and Biological Samples

Flavonoids are plant-derived compounds that have several health benefits, including antioxidative, anti-inflammatory, anti-mutagenic, and anti-carcinogenic effects. Quercetin is a flavonoid that is widely present in various fruits, vegetables, and drinks. Accurate determination of quercetin in different samples is of great importance for its potential health benefits. This review, is an overview of sample preparation and determination methods for quercetin in diverse matrices. Previous research on sample preparation and determination methods for quercetin are summarized, highlighting the advantages and disadvantages of each method and providing insights into recent developments in quercetin sample treatment. Various analytical techniques are discussed including spectroscopic, chromatographic, electrophoretic, and electrochemical methods for the determination of quercetin and its derivatives in different samples. UV-Vis (Ultraviolet-visible) spectrophotometry is simple and inexpensive but lacks selectivity. Chromatographic techniques (HPLC, GC) offer selectivity and sensitivity, while electrophoretic and electrochemical methods provide high resolution and low detection limits, respectively. The aim of this review is to comprehensively explore the determination methods for quercetin and quercetin glycosides in diverse matrices, with emphasis on pharmaceutical and biological samples. The review also provides a theoretical basis for method development and application for the analysis of quercetin and quercetin glycosides in real samples.

Green and Low-temperature Synthesis of Carbon Dots for Simple Detection of Kaempferol

As a common flavonols, kaempferol (Kae) has a broad market as health food and medicine for its anti-inflammatory, anti-oxidation, and anti-cancer properties. In this study, a novel convenient and simple fluorescent sensor based on carbon dots (CDs) for the detection of Kae was developed. The fluorescent CDs, with excellent photo-luminescence (PL) and up-conversion luminescence (UCPL) properties, were successfully prepared by low-temperature oil bath reaction based on ascorbic acid as carbon source at 90 °C in one pot. Under the optimal conditions, the fluorescence (FL) intensity of CDs was gradually quenched by the increasing addition of Kae with a linear relationship between F0/F and Kae concentration in a wide range from 5 µM to 100 µM with a detection limit of 0.38 µM. And this designed sensor was favourably applied for the detection of Kae in actual sample (xin-da-kang tablets). Moreover, the proposed CDs has great application prospects as a drug-sensor for detecting Kae due to its simple operation, economical and green materials, low equipment requirement, and rapid detection.

Electrostatic Self-Assembly of MXene on Ruthenium Dioxide-Modified Carbon Cloth for Electrochemical Detection of Kaempferol

A superior composite material consisting of MXene and ruthenium dioxide-modified carbon cloth is synthesized by pulsed laser deposition and electrostatic self-assembly, which is further utilized to construct a class of novel electrochemical (EC) sensors for kaempferol (KA) detection. The carbon-cloth-based electrodes modified by ruthenium dioxide and then MXene are characterized by X-ray diffraction, scanning electron microscope, and X-ray photoemission spectroscopy. The EC process on the modified electrodes is analyzed by cyclic voltammetry, EC impedance spectroscopy, and differential pulse voltammetry. It is found that positively charged RuO2 not only possesses the remarkable electrical conductivity and electrocatalysis activity but also hampers the restacking of MXene, which accordingly enhances the exposure of the active surface area and greatly boosts the electrocatalysis activity of the entire composite. Consequently, this newly developed composite-based EC sensor exhibits a high sensitivity, selectivity, and remarkable stability to detect KA with two linear ranges of 0.06-1 and 1-15 µM. The inferred limit of detection is 0.039 µM via differential pulse voltammetry. More importantly, this novel EC sensor is found to be applicable for detecting KA in practical traditional Chinese medicines.

Metal-Organic Framework with Near-Infrared Luminescence for "Switch-on" Determination of Kaempferol and Quercetin by the Antenna Effect

The establishment of a reliable and sensitive method for the detection of flavonoids, such as kaempferol (Kae) and quercetin (Que), is important and challenging in food chemistry and pharmacology because numerous structural analogues may interfere with the detection. Until now, designing an efficient switch-on fluorescence sensing strategy for Kae and Que was still in the unachievable stage. In this work, a switch-on near-infrared (NIR) luminescence sensing assay for Kae and Que was fabricated based on a metal-organic framework (MOF) called IQBA-Yb for the first time. The fluorescence enhancing mechanism was that analytes served as additional "antenna" of Yb³⁺, leading to the efficient switch-on NIR emission under excitation at 467 nm. Meanwhile, the combination results of experiment and theoretical calculation revealed that there existed hydrogen bonds between Kae, Que, and the MOF skeleton, further promoting the energy transfer between the analyte and Yb³⁺ and facilitating fluorescence enhancement response. The developed probe possessed excellent sensing capability for Kae and Que, accompanied by a wide linear range (0.04-70, 0.06-90 μM), low detection limit (0.01, 0.06 μM), and short response time (20 min, 6 min), which was used to determine the Kae and Que contents in Green Lake and eatable Que samples with satisfactory results.

A new hybrid nanocomposite electrode based on Au/CeO2-decorated functionalized glassy carbon microspheres for the voltammetric sensing of quercetin and its interaction with DNA

A new hybrid composite containing cerium oxide nanoparticle (CeO2NP) and gold nanoparticle (AuNP)-decorated functionalized glassy carbon microspheres (FGCM) was synthesized (Au/CeO2@FGCM). As a result, an Au/CeO2@FGCM-paraffin oil paste electrode (PE) (Au/CeO2@FGCM-PE) was fabricated and employed for the voltammetric sensing of quercetin (QRT). The structure and surface morphology of Au/CeO2@FGCM were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) were employed for the investigation of the electrochemical behavior of Au/CeO2@FGCM-PE. Under the optimum conditions, the SWV oxidation peak current showed linear dependence on the QRT concentration in the range from 48 nM to 1.09 μM. The achieved limits of detection and quantitation were 0.37 nM and 1.22 nM, respectively. Au/CeO2@FGCM-PE was reproducible, sensitive and stable and displayed anti-interference ability for various common interferents. The proposed method was also successfully applied for real sample analysis. The QRT content extracted from natural sources was determined, and satisfactory results were achieved. Furthermore, the interaction of QRT with salmon testes and calf thymus dsDNA (st-DNA and ct-DNA) on Au/CeO2@FGCM-PE was studied by CV and SWV. The corresponding binding constant (K), surface concentration (Γ), and Gibbs free energy (ΔG°) were computed for the free QRT and the bound QRT-dsDNA complex. The calculated K values for the QRT-ct-DNA and QRT-st-DNA complexes were found to be 6.24 × 105 M-1 and 3.63 × 105 M-1, respectively, which revealed that QRT strongly interacted with ct-DNA compared to that with st-DNA. The decreased intensity of the QRT oxidation peak resulting from its interaction with dsDNA provides a chance to use QRT as a new indicator to analyze ct-DNA and st-DNA.

Highly sensitive and selective optosensing of quercetin based on novel complexation with yttrium ions

A simple and fast method was developed for the determination of quercetin. The concentration of quercetin can be determined based on the fluorescence emission resulting from the coordinative interactions between quercetin and the yttrium ion (Y³⁺). Notably, a portable platform to quantitatively analyze quercetin was constructed. This platform incorporates our custom-built homemade reader based on a photodiode, and Arduino hardware, which accepts a paper ribbon on which Y³⁺ is deposited as an input. In addition, the color change of the paper ribbon was identified using a smartphone via the hue values of the photographs. The limits of detection for quercetin using spectroscopy, a smartphone, and a custom-built reader were calculated to be 27, 110, and 129 nM, respectively. The use of a custom-built device and a smartphone for detecting quercetin via fluorescence from the prepared paper ribbon reduces the time and cost of quercetin detection. This approach could be employed for on-site sensing of quercetin in real samples.

Electrochemical Evaluation of the Total Antioxidant Capacity of Yam Food Samples on a Polyglycine-Glassy Carbon Modified Electrode

Background:

The total antioxidant capacity of yam food grown in southern African regions was investigated by a polyglycine-glassy carbon modified electrode. The modified electrode was fabricated using glycine solution on glassy carbon electrode by electrodeposition method. The proposed modified electrode is found to be nearly 3.15-fold more sensitive than the bare electrode. For the measurement of the total antioxidants of yam, differential pulse stripping voltammetry (DPSV) was employed with standard quercetin compound.

Methods:

The total antioxidant capacity of yam was deduced by DPSV and cyclic voltammetry (CV) methods. The basic parameters for the stripping technique such as pH, accumulation time and accumulation potential were optimized as 20 s, 200 mV and a pH of 3 Britton-Robinson (B-R) buffer solutions in 0.5 mg quercetin/L, respectively.

Results:

In the optimization condition, the linear working range was determined between 5.0 μg/L and 80.0 µg/L for the quercetin. The detection (LOD) and quantification (LOQ) limits of quercetin were found to be 0.39 µg/L and 1.39 µg/L on the modified electrode by DPSV, respectively. The procedure was also applied to natural yam samples and total antioxidant capacity of 0.1 kg of yam was determined as 96.15 ± 0.85 µg/L of equivalent quercetin at 95% confidence level with the relative standard deviations of 0.88%.

Conclusion:

Sensitive and selective voltammetric method was developed for the determination of total antioxidant capacity in yam. Moreover, the modified polyglycine-glassy carbon electrode was constructed more selectively for quercetin. As a result, a simple, sensitive and rapid new voltammetric method for the determination of antioxidants has been developed using the modified electrode.

Sr-Doped NiO3 nanorods synthesized by a simple sonochemical method as excellent materials for voltammetric determination of quercetin

A fabricated Sr-doped NiO₃ nanorod-modified GCE was developed for electrochemical sensing of quercetin.

Excitation-independent emission carbon nanoribbon polymer as a ratiometric photoluminescent probe for highly selective and sensitive detection of quercetin

In this study, sulfur–nitrogen co-doped carbon nanoribbon (SNCNR) polymers with stable dual-emission fluorescence were synthesized using a one-step traditional hydrothermal method of 6-mercaptopurine in an aqueous methanol solution.

A glassy carbon electrode modified with a copper tungstate and polyaniline nanocomposite for voltammetric determination of quercetin

A binary nanocomposite of type copper tungstate and polyaniline (CuWO₄@PANI) is described that was obtained by single step polymerization on the surface of a glassy carbon electrode (GCE). The resulting electrode is shown to be a viable tool for voltammetric sensing of quercetin (Qn) in blood, urine and certain food samples. The nanocomposite was characterized by UV-visible absorption spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and high-resolution transmission electron microscopy. Differential pulse voltammetry was applied to quantify Qn, typically at the relatively low working potential of 0.15 V (vs. Ag/AgCl). The modified GCE has a wide analytical range (0.001-0.500 μM) and a low detection limit (1.2 nM). The sensor is reproducible, selective and stable. This makes it suitable for determination of Qn in real samples without complicated sample pretreatment. Graphical abstract Schematic of a copper tungstate and polyaniline nanocomposite modified glassy carbon electrode for voltammetric determination of quercetin in real samples.

Hexammine cobalt(iii) coordination complex grafted reduced graphene oxide composite for sensitive and selective electrochemical determination of morin in fruit samples

The RGO/[Co(NH₃)₆]³⁺/GCE modified GCE was potentially applied for the electrochemical detection of MR.

Antioxidant and anti-dermatophytic properties leaf and stem bark of Xylosma longifolium clos

BACKGROUND

The present study was carried out to assess the phytochemical and anti-dermatophytic effect of the leaf and bark extracts of Xylosma longifolium Clos. The leaf and stem bark are used by the indigenous people of Manipur, India for treatment of skin diseases.

METHODS

The leaves and stem barks of Xylosma longifolium were extracted using petroleum ether, chloroform and methanol respectively. The different extracts of each plant parts were tested for antioxidant activity using DPPH assay. The phenolic content was assayed using Folin-Ciocalteu colorimetric method. Each extracts was further analysed by RP-HPLC to quantify some individual flavonoid components. The anti-dermatophytic activity was evaluated both by agar diffusion method and micro wells dilution method against the Microsporum boullardii MTCC 6059, M. canis (MTCC 2820 and MTCC 32700), M. gypseum MTCC 2819, Trichophyton ajelloi MTCC 4878, T. rubrum (MTCC 296 and MTCC 3272).

RESULTS

The free radical scavenging activity values were ranged from 0.7 to 1.41 mg/ml and 0.6 to 1.23 mg/ml, respectively for leaf and stem bark extracts. The amount of total phenolic contents of the extracts occurred in both leaf and bark in the range of 12 to 56.6 mg GAE/100 g and 16 to 58 mg GAE/100 g respectively. RP-HPLC analysis for flavonoids revealed the presence of two major flavonoid compounds, rutin and catechin. Kaempferol was in trace or absent. Methanol leaf extract showed significant low inhibitory effect against tested fungus Trichophyton ajelloi MTCC 4878 (0.140625 mg/ml) as the most sensitive. These finding suggest that the methanol leaf extract tested contain compounds with antimicrobial properties.

CONCLUSION

The results of our study may partially justify the folkloric uses on the plant studied and further provide an evidence that the leaf extract of Xylosma longifolium might be indeed a potential sources of antimicrobial agents.

Research progress on flavonoids isolated from traditional Chinese medicine in treatment of Alzheimer's disease

Alzheimer's disease (AD) is a severe condition in aging countries. The currently used drugs including donepezil, rivastigmine, galantamine, and memantine are effective in managing the symptoms. However, they are hardly capable of preventing, halting, or reversing the disease. In the long history of development of traditional Chinese medicine, much experience has accumulated and is summarized in treatment of diseases that correspond to the concept of AD. In recent years, exploration of natural active ingredients from medicinal herbs for treatment of AD has attracted substantial attention. Some flavonoids have been revealed to have a variety of biological actions such as scavenging free radicals, inhibiting neuron apoptosis, and nurturing neuronal cells that constitute the basis for treatment of AD. In this article, we review recent research progress on flavonoids isolated from traditional Chinese medicine against AD and their underlying mechanisms.

Simultaneous determination of the flavonoids robinin and kaempferol in human breast cancer cells by liquid chromatography-tandem mass spectrometry

An accurate, precise and sensitive method was developed and validated for the simultaneous quantification of the flavonoid glycoside robinin, and its algycone kaempferol in human breast cancer MCF-7 cells. The application of liquid chromatography-tandem mass spectrometry (LC/MS/MS) with a TurboIonspray interface in negative mode under multiple reactions monitoring was investigated. Chromatographic separation was achieved on a C(18) column using a mobile phase consisting of (A) water with 0.025% formic acid and 1mM ammonium formate and (B) acetonitrile with 0.025% formic acid. Rutin was used as the internal standard for robinin and fisetin as the internal standard for kaempferol. The assay had a limit of detection of 0.1ng/ml for both compounds when present in cell lysate. The calibration curves were linear from 1 to 250ng/ml (r>0.999) for each compound. The intra- and inter-day coefficients of variation were less than 10% and intra- and inter-day accuracies were within 11%. This assay was successfully applied in a robinin cellular uptake study to determine the intracellular concentrations of robinin in MCF-7 cells.

Dietary quercetin exacerbates the development of estrogen-induced breast tumors in female ACI rats

Phytoestrogens are plant compounds that structurally mimic the endogenous estrogen 17beta-estradiol (E(2)). Despite intense investigation, the net effect of phytoestrogen exposure on the breast remains unclear. The objective of the current study was to examine the effects of quercetin on E(2)-induced breast cancer in vivo. Female ACI rats were given quercetin (2.5 g/kg food) for 8 months. Animals were monitored weekly for palpable tumors, and at the end of the experiment, rats were euthanized, breast tumor and different tissues excised so that they could be examined for histopathologic changes, estrogen metabolic activity and oxidant stress. Quercetin alone did not induce mammary tumors in female ACI rats. However, in rats implanted with E(2) pellets, co-exposure to quercetin did not protect rats from E(2)-induced breast tumor development with 100% of the animals developing breast tumors within 8 months of treatment. No changes in serum quercetin levels were observed in quercetin and quercetin+E(2)-treated groups at the end of the experiment. Tumor latency was significantly decreased among rats from the quercetin+E(2) group relative to those in the E(2) group. Catechol-O-methyltransferase (COMT) activity was significantly downregulated in quercetin-exposed mammary tissue. Analysis of 8-isoprostane F(2alpha) (8-iso-PGF(2alpha)) levels as a marker of oxidant stress showed that quercetin did not decrease E(2)-induced oxidant stress. These results indicate that quercetin (2.5 g/kg food) does not confer protection against breast cancer, does not inhibit E(2)-induced oxidant stress and may exacerbate breast carcinogenesis in E(2)-treated ACI rats. Inhibition of COMT activity by quercetin may expose breast cells chronically to E(2) and catechol estrogens. This would permit longer exposure times to the carcinogenic metabolites of E(2) and chronic exposure to oxidant stress as a result of metabolic redox cycling to estrogen metabolites, and thus quercetin may exacerbate E(2)-induced breast tumors in female ACI rats.

Stereoselective transport and uptake of propranolol across human intestinal Caco-2 cell monolayers

The transport and uptake of individual propranolol (PPL) enantiomers were studied in human intestinal Caco-2 cell monolayers, and a reversed-phase HPLC-UV assay was used for quantitative analysis. S-PPL and R-PPL across Caco-2 cell monolayers was determined in the concentrations range of 10-500 microM in both apical (AP) to basolateral (BL) and BL to AP directions. S-PPL exhibited greater permeability than R-PPL in the AP to BL direction, whereas in the BL to AP direction S-enantiomer transported less than R-enantiomer. Uptake of R-PPL was significantly higher than that of S-PPL either from AP side or from BL side. The statistically significant differences in uptake were observed at the concentrations range from 10 to 50 microM. Furthermore, the apparent Michaelis constant (K(m)) and maximal velocity (V(max)) also showed significant difference between the two enantiomers. Moreover, the AP to BL transport of PPL enantiomer was markedly decreased by lowering the pH of the apical side but it did not affect the stereoselectivity of PPL across Caco-2 cell monolayers. The transport and uptake of PPL in the BL to AP direction was not influenced by several protein inhibitors. The results suggest that PPL enantiomers showed stereoselective transport and uptake across the Caco-2 cell monolayers. A special transport mechanism capable of directing the PPL enantiomers might be present in the Caco-2 monolayers.

Development and validation of a sensitive reversed-phase HPLC method to determine intracellular accumulation of hydroxycamptothecin

The intracellular accumulation of anti-cancer agents strongly influences the efficiency of chemotherapy for cancer. In the present study, a simple, rapid, sensitive reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed and validated to determine hydroxycamptothecin (HCPT) in Eca109 cells. HCPT in cellular lysis solution were measured by RP-HPLC with a C18 column after extraction with ethyl acetate. The mobile phase contained 0.1% triethylamine-phosphoric acid buffer (pH 3.0) and acetonitrile (75:25, v/v). Fluorescence detector with excitation and emission wavelengths of 382 and 528 nm was used for determination of HCPT. The calibration curve was linear from 2 to 100 ng/ml with correlation coefficient of 0.9999, while the limit of quantification is 2 ng/ml. The recovery of assay was between 86.5 and 105.2%. The intra- and inter-day coefficients of variation were less than 10% (R.S.D.). Furthermore, the validated method was used to determine the accumulation of HCPT after incubating the liposomal formulation of HCPT and HCPT for injection with the intact cells. HCPT liposomes showed higher intracellular accumulation of HCPT at different incubation times compared with that of conventional HCPT injection.