Determination of flavonoids by high-performance liquid chromatography and capillary electrophoresis

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.

Anticancer plant-derivatives: deciphering their oncopreventive and therapeutic potential in molecular terms

Background

Over the years, phytomedicines have been widely used as natural modalities for the treatment and prevention of various diseases by different ethnic groups across the globe. Although, 25% of drugs in the USA contain at least one plant-derived therapeutic compound, currently there is a paucity of plant-derived active medicinal ingredients in the pharmaceutical industry. Scientific evidence-based translation of plant-derived ethnomedicines for their clinical application is an urgent need. The anticancer and associated properties (antioxidative, anti-inflammatory, pro-apoptotic and epithelial-mesenchymal transition (EMT) inhibition) of various plant extracts and phytochemicals have been elucidated earlier. Several of the plant derivatives are already in use under prophylactic/therapeutic settings against cancer and many are being investigated under different phases of clinical trials.

Main body

The purpose of this study is to systematically comprehend the progress made in the area of prophylactic and therapeutic potential of the anticancerous plant derivatives. Besides, we aim to understand their anticancer potential in terms of specific sub-phenomena, such as anti-oxidative, anti-inflammatory, pro-apoptotic and inhibition of EMT, with an insight of the molecules/pathways associated with them. The study also provides details of classes of anticancer compounds, their plant source(s) and the molecular pathway(s) targeted by them. In addition to the antioxidative and antiproliferative potentials of anticancer plant derivatives, this study emphasizes on their EMT-inhibition potential and other ‘anticancer related’ properties. The EMT is highlighted as a phenomenon of choice for targeting cancer due to its role in the induction of metastasis and drug resistance. Different phytochemicals in pre-clinical or clinical trials, with promising chemopreventive/anticancer activities have been enlisted and the plant compounds showing synergistic anticancer activity in combination with the existing drugs have been discussed. The review also unravels the need of carrying out pan-signalome studies for identifying the cardinal pathways modulated by phytomedicine(s), as in many cases, the molecular pathway(s) has/have been randomly studied.

Conclusion

This review systematically compiles the studies regarding the impact of various plant derivatives in different cancers and oncogenic processes, as tested in diverse experimental model systems. Availability of more comprehensive information on anticancer phyto-constituents, their relative abundance in crude drugs, pathways/molecules targeted by phytomedicines, their long-term toxicity data and information regarding their safe use under the combinatorial settings, would open greater avenues of their utilization in future against this dreaded disease.

Graphical Abstract

Optimization of tannin extraction from coconut coir through response surface methodology

Coconut coir is produced by extracting tiny grains of coir from coconut shell, which is an agricultural product that is abundant in Thailand. Coir is typically discarded, but it is a useful material because it contains tannins. Tannin is a polyphenolic compound that is prevalent in the plant kingdom, including in wood, bark, rhizomes, roots, and fruits. In this study, we extracted tannins from coconut coir using two types of solvents: water and ethanol. Optimization of the tannin content was achieved via RSM (response surface methodology) with the assistance of Design-Expert software. Meanwhile, the temperature (30-70 °C), ratio of solid to solvent (1:20-1:40), and solvent type (water or ethanol) were optimized via central composite design (CCD). The optimum model using analysis of variance revealed R² = 0.9825, and adj.R² = 0.9687. Temperature is affected by tannin content, and high temperatures result in a higher tannin content when using water than when using ethanol. Optimum conditions for coconut coir extraction using water with ethanol include a ratio for solid to solvent of 1:30 and the temperature set to 70 °C. The validated model exhibits errors of 8.24 and 11.08% for water and ethanol, respectively. Confirmation of the presence of tannins in the crude extract was carried out via Fourier-transform infrared spectroscopy and through the use of liquid chromatography with tandem mass spectrometry.

Fluorescence determination of quercetin in food samples using polyhedron-shaped MOF@MOF(NUZ-8) based on NH2-UiO-66 and ZIF-8

A new metal-organic framework compound (MOF@MOF, NUZ-8) comprised of NH₂-UiO-66 and ZIF-8 under the polyvinylpyrrolidone (PVP) as the structure modifier was synthesized through an internal extended growth method (IEGM). The resulting NUZ-8 emerged the unreported unique polyhedron shape and showed considerable specific surface area (1466.1862 m²/g), excellent adsorption capacity, and fluorescence. NUZ-8 was used as a probe for the rapid optical detection of natural antioxidant quercetin (QCT). Its outstanding selectivity and sensitivity to QCT are derived from the fact that NH₂-UiO-66 acted as an optical tentacle to perceive QCT in virtue of its luminescence advantages, and ZIF-8 realized the selective enrichment of the QCT through its electron-rich framework structure. The experiments were carried out at an excitation wavelength of 335 nm and an emission wavelength range of 370-530 nm. Under conditions of the investigation, this probe realized the rapid detection of QCT and considerable adsorption capacity with wide linearity (0.3-80 μM), a low detection limit (0.14 μM), and acceptable recoveries (84.0-97.0%) in red wine samples, properties which were superior to many other detection platforms. The synthesis and the use of the above polyhedral composite provide guidance for the application of the IEGM in enhancing chemical sensing and instant determination of drugs.Graphical abstract Flow chart of this paper.

Effect of Lonicera japonica extract on lactation performance, antioxidant status, and endocrine and immune function in heat-stressed mid-lactation dairy cows

Here, we examined the effects of Lonicera japonica extract (LJE) on lactation performance, antioxidant status, and endocrine and immune function in heat-stressed mid-lactation dairy cows. Twenty-four healthy Chinese Holstein mid-lactation dairy cows, all with similar milk yield (30.0 ± 1.0 kg/d), parity (2.5 ± 0.3), and days in milk (105 ± 5 d) were allocated to 4 groups using a randomized complete block design: a negative control group (without LJE supplementation; CON) and groups that received LJE at 14, 28, and 56 g/d. The experiment lasted 10 wk over a hot summer, with a pre-feeding period of 2 wk. Cows were exposed to heat stress, as the average temperature-humidity index was greater than 72. The results showed that LJE had no effect on respiration rate; however, it reduced the rectal temperature of dairy cows experiencing heat stress in both a linear and quadratic manner; the lowest (39.03°C) was recorded for the LJE-28 group, lower than the CON group. Supplementation with LJE did not affect dry matter intake, milk yield, or milk composition. The majority of biochemical parameters in serum were unaffected by supplementation with different amounts of LJE; the exception was creatinine, which was reduced quadratically. Compared with the CON group, serum triiodothyronine concentrations increased significantly in the LJE-28 group. Addition of LJE to the diet increased thyroxine concentrations quadratically; values peaked at 18.62 ng/mL in the LJE-28 group. Furthermore, supplementation with increasing amounts of LJE quadratically increased the activity of glutathione peroxidase and total antioxidant capacity in serum but decreased concentration of malondialdehyde. Although we detected no differences in the concentrations of IgA, IgM, or cytokines, dairy cows in the LJE-28 group had higher IgG and IL-4 concentrations than did cows in the CON group. Supplementation with LJE increased concentrations of IgG and IL-4 in the serum quadratically but decreased that of IL-2. Finally, heat shock protein 72 concentrations in the serum tended to fall quadratically as the amount of LJE increased. In summary, LJE had no negative effects on lactation performance but helped to alleviate heat stress by improving antioxidant status and promoting endocrine and immune functions. Supplementation with LJE at 28 g/d is recommended for lactating dairy cows experiencing heat stress during hot summers.

Development of a rapid and accurate UHPLC-PDA-FL method for the quantification of phenolic compounds in grapes

Grapes are a great source of phenolic compounds, which have excellent antioxidant properties. Efficient analytical methods are necessary to selectively and precisely determine these compounds content in grapes. In this study, a reverse-phase ultra-high performance liquid chromatography (UHPLC) method with fluorescence and photodiode array detection has been developed to determine and quantify 27 of the main phenolic compounds present in grapes. An ACQUITY UPLC® BEH C18 (50 mm × 2.1 mm i.d., 1.7 mm particle size) column was employed. A gradient method was developed and column temperature (25-55 °C), as well as flow rate (0.6-0.75 mL min^-1), were optimized. The optimum conditions allowed the separation of all the compounds in less than 9 min. The method was validated and demonstrated excellent detection and quantification limits, precision, and selectivity. Finally, several grape varieties were studied in order to demonstrate the applicability of the method to the analysis of real matrix samples.

Analysis of Natural Dyes from Historical Objects by High Performance Liquid Chromatography and Electromigration Techniques

Based on material published between 1989 and 2018 in this paper high performance liquid chromatography and electromigration techniques used in studies of natural dyes that can be found in historical objects are rewieved. Different aspects of analysis have been discussed: the stationary and mobile phase, the choice of sample solvent, methods of extraction and detection, including sensitivity parameters, such as LOD and/or LOQ. The discussed dyes have been divided into three categories (a) red antraquinone dyes along with dyes extracted from bark and tree juices, (b) yellow flavonoid dyes and saffron and (c) blue indigoid dyes. The main markers (chromophores or auxochromes) typical for each dye source were presented which allows to identify specific species of source plants and animals. The first part of the study involved the analysis of most critical findings when it comes to HPLC or represented an significant analytical approach. The second part of the study is focused on different aspects of electromigration techniques application in analysis of natural dyes with special attention paid on such parameters as the running buffer/mobile phase composition and sample solvent. Detection methods along with LOD and LOQ comparison in HPLC and electromigration techniques were also discussed. Methods of sample preparation, such as hydrolysis and extraction, used in HPLC and electromigration techniques were also briefly discussed.

Screening of secondary metabolites in cladodes to further decode the domestication process in the genus Opuntia (Cactaceae)

During their domestication process, the species of the genus Opuntia lose their ability to survive in the wild. Presence and concentration of secondary metabolites which play a role in the interaction with their surroundings are modified but without an identifiable pattern. A domestication gradient based on morphological characteristics has been previously described for the species in the Opuntia genus. Secondary metabolites are a diverse group of bioactive compounds that relate to a species evolution, both in their natural and artificial (domestication process) selection environments. In addition, these compounds are associated with plant resistance to stress when growing in the wild. A comprehensive characterization of secondary metabolite profiles in the Opuntia genus that accounts for the genotypic differences related to the degree of domestication has not previously been conducted. This study evaluated the phytochemical composition of young cladodes from fifteen variants, of O. ficus-indica, O. albicarpa Sheinvar, and O. megacantha Salm-Dyck, identified as species with a highly advanced, advanced and intermediate degree of domestication, respectively, and O. hyptiacantha A. Web, and O. streptacantha Lem. identified as wild-intermediate and wild species. Analyses were carried out using a HPLC-diode array detection technique. Out of the 13 identified and quantified phenolic molecules and terpenoids, only the caffeic, ferulic and syringic acids, and the terpenoid β-amyrin were present in all variants. The flavonoid luteolin was absent in all five species. Gallic, vallinic, p-hydroxybenzoic, chlorogenic and p-coumaric acids were only present in 53-87% of variants; flavonoids quercetin, isorhamnetin, rutin and apigenin in 47-87% of the variants. Both, oleanolic acid and peniocerol, were present only in 60% of variants. Isorhamnetin was absent in O. hyptiacantha and quercetin in O. streptacntha. Differences and similarities in the secondary metabolites content showed no recognizable trend relating to the degree of domestication across the species in this genus.

Data on the optimization and validation of HPLC-PDA method for quantification of thirty polyphenols in blackthorn flowers and dry extracts prepared thereof

This paper presents data on the optimization and validation of an RP-HPLC-PDA method for quantification of 30 phenolic constituents of the blackthorn (Prunus spinosa L.) flower. The method development data cover detailed descriptions of the optimization process in terms of elution solvents, gradient profile, temperature, and flow rate. The validation data cover accuracy and precision (intra- and inter-day variability) for retention times and peak areas. Moreover, the quantification data for the commercial samples of blackthorn flower (different manufactures and years of collection), as well as for the extracts (of different polarity) prepared thereof, are included. The data presented here were related to the article: "Simultaneous quantification of thirty polyphenols in blackthorn flowers and dry extracts prepared thereof: HPLC-PDA method development and validation for quality control" [1].

Comparative Transcriptome Analysis of Celery Leaf Blades Identified an R2R3-MYB Transcription Factor that Regulates Apigenin Metabolism

Apigenin has been proven to possess many pharmacological properties, but the mechanism of regulation of apigenin biosynthesis in plants remains unclear. Apigenin is the main flavonoid in celery and is mainly accumulated in the middle stage of leaf blade development. In this study, comparative transcriptomic analysis revealed a large number of structural genes and transcription factor genes that may be involved in the apigenin metabolic pathway. On the basis of the apigenin content in different celery accessions, an R2R3-MYB transcription factor gene, named AgMYB1, was isolated from the high apigenin celery accession C014. Bioinformatics analysis indicated that AgMYB1 may be involved in flavonoid metabolism. AgMYB1 expression showed a positive relation with the expression of the apigenin accumulation marker gene FNSI and with the apigenin content in different celery tissues. Moreover, overexpression and antisense expression of AgMYB1 in transgenic celery plants significantly increased and reduced the expression of apigenin biosynthetic genes and the apigenin content, respectively. These findings suggest that AgMYB1 is involved in positive regulation of apigenin metabolism in celery.

Flavonoid loaded nanoparticles as an effective measure to combat oxidative stress in Ribonuclease A

Flavonoids like quercetin and myricetin serve as naturally occurring antioxidants but their bioactivity is limited due to low aqueous solubility and oxidation under physiological conditions. In this current study, the antioxidant activity of quercetin and myricetin loaded chitosan nanoparticles during the induced oxidation of Ribonuclease A (RNase A) has been compared with the corresponding free flavonoids. Oxidation of RNase A leads to intermolecular dityrosine (DT) bond formation which shows a characteristic fluorescence emission around 405 nm. Although both quercetin and myricetin loaded nanoparticles initially exhibit lower antioxidant property compared to the free flavonoids, however, with increase in oxidant concentration over time the DT fluorescence showed greater increase for free flavonoids in comparison to the nanoparticles. The polyphenol loaded nanoparticles are also found to be effective in preventing bacterial cell damage in oxidizing medium. The slow release of flavonoids from the nanoparticles is responsible for their prolonged antioxidant effect in the oxidizing medium unlike the free flavonoids which are exhausted almost completely in the initial phase.

AgMYB2 transcription factor is involved in the regulation of anthocyanin biosynthesis in purple celery (Apium graveolens L.)

This study showed that an R2R3-MYB transcription factor, AgMYB2, functions in anthocyanin biosynthesis and accumulation in purple celery. Anthocyanins are involved in tissue coloration and stress response in plants. Foods containing high anthocyanin content are also beneficial to human health. Purple celery accumulated amounts of anthocyanins in the petioles. The biosynthesis of anthocyanin in plants is mainly regulated by the R2R3-MYB transcription factor (TF). However, the R2R3-MYB TF that controls anthocyanin accumulation in purple celery remains unclear. In this study, an R2R3-MYB TF gene, AgMYB2, was cloned from purple celery and characterized as anthocyanin biosynthetic regulator. Sequence analysis indicated that AgMYB2 contained highly conserved R2R3 domain and two anthocyanin characteristic motifs, ANDV motif and KPRPR[S/T]F motif. The relative expression level of AgMYB2 in purple celery was significantly higher than that in non-purple celery at three developmental stages. Heterologous expression of AgMYB2 in Arabidopsis generated more anthocyanins and resulted in dark-purple leaves and flowers. The expression levels of anthocyanin biosynthetic genes and the antioxidant activity of transgenic Arabidopsis carrying AgMYB2 were up-regulated. The determination of anthocyanin glycosylation activity of Arabidopsis crude enzyme verified the anthocyanin biosynthesis regulatory function of AgMYB2 at the protein level. The interaction between AgMYB2 and bHLH proteins was shown by yeast two-hybrid assay. The results will help to elucidate the molecular mechanism of anthocyanin biosynthesis in purple celery and provide an approach for cultivating plants with high anthocyanin content.

Gold Nanocage-Based Electrochemical Sensing Platform for Sensitive Detection of Luteolin

A simple and sensitive electrochemical sensor was developed for the detection of tracelevels of luteolin. The sensoris based on a novel type of chemically modified electrode: gold nanocage (AuNCs)-modified carbon ionic liquid electrode (CILE). To construct this electrochemical sensing platform for luteolin, CILE is initially prepared by using 1-hexylpyridinium hexafluorophosphate as the binder and then AuNCs are coated on the surface of CILE to fabricate AuNCs-modified CILE (AuNCs/CILE). Electrochemical studies have shown that AuNCs/CILE can exhibit enhanced electrocatalytic activity toward the redox reaction of luteolin, therefore, the redox peak current of luteolin can be greatly improved, resulting in the high sensitivity of the developed sensor. Under the optimal conditions, the oxidation peak currents of the sensor increase linearly with an increase in the luteolin concentration in a range from 1 to 1000 nM with a detection limit of 0.4 nM, which is lower than those of most reported electrochemical luteolin sensors. Moreover, the reproducibility, precision, selectivity, and stability of this sensor are excellent. Finally, the sensing system was applied to the analysis of luteolin-spiked drug samples and the recovery in all cases was 95.0–96.7%, indicating the potential application of this simple, facile, and sensitive sensing system in pharmaceutical analysis.

Quantitative separation of hesperidin, chrysin, epicatechin, epigallocatechin gallate, and morin using ionic liquid as a buffer additive in capillary electrophoresis

Recently, an increasing interest has been observed in ionic liquids (ILs) due to their potentialities in various chemical processes. ILs have some unique properties making them excellent additives in CE. In this work a simple, rapid, and reliable CZE method has been developed and validated using 1-butyl-3-methyl imidazolium hexafluorophosphate (BMIM-PF₆ ) ionic liquid as a buffer additive for the determination/separation of five flavonoids including hesperedin, epicatechin (EC), epigallocatechin gallate (EGCG), and morin using photodiode array (PDA) detector. The effect of several parameters such as concentration and pH of the running buffer, applied voltage, and concentration of ionic liquid were optimized. CZE at 25°C with 25 mM borate buffer of pH 9.0 at an applied voltage of 17 kV by adding 17.5 mM of IL was found to be suitable for the separation/determination of all five analytes within 08 min. Validation of the method was performed in terms of linearity, accuracy, precision, and limit of detection and quantification. The calibration curves were plotted in the concentration range of 1-200 μg/mL for all five analytes. The response was linear with R²  = 0.990 for EC, chrysin, and hesperidin, 0.992 for morin, and 0.988 for EGCG. LOD and LOQ were obtained within the range of 0.4-0.5 and 1.4-1.7 μg/mL, respectively. The proposed method showed good reproducibility with RSD of less than 3% for both migration time and peak height. The method was successfully applied for the determination of flavonoids from citrus fruits and tea samples.

A novel multi-purpose enzymatic system and procedures for the rapid fluorescent determination of flavonoids in herbal pharmaceuticals and plant materials

The paper presents a novel multi-purpose enzymatic system and procedures for fluorescent determination of several flavonoids in herbal pharmaceuticals and plant materials after their enzyme-catalyzed oxidation by hydrogen peroxide and further derivatization with meso-1,2-diphenylethylenediamine. This system may be used for rapid (15-30min/20 samples) simultaneous screening of samples containing a certain flavonoid in a standard microplate, or as a HPLC detection system for analyzing plant extracts with uncertain composition. In the first case, this indicator system provides sensitive and reproducible microplate determination of quercetin, epicatechin, caffeic acid, and taxifolin in the ranges 0.1-5, 1-10, 0.1-10, 0.5-5μM, respectively. In the second case, quercetin, epicatechin, and caffeic acid can be determined in the ranges 0.05-0.75, 0.05-0.75, and 0.01-0.75µg/ml (0.16-2.5, 0.17-2.6, 0.06-4.2μM), respectively. We have demonstrated the application of the system for the analysis of 3 pharmaceuticals and 3 types of plants.

A Capillary Electrophoresis Electrospray Ionization-Mass Spectrometry Method using a Borate Background Electrolyte for the Fingerprinting Analysis of Flavonoids in Ginkgo biloba Herbal Supplements

A laboratory-built sheath liquid capillary electrophoresis-mass spectrometry interface was used to develop a qualitative method for fingerprinting analysis of 14 structurally similar flavones, flavonols, flavonones, and several representative glycosides in plant samples. The migration order of the flavonoids was dependent on a the number of hydroxyl groups present on the flavonoid B-ring, extent of conjugation, number of glycosidic functionalities, and ability of the flavonoid to form stable borate complexes with the background electrolyte. Parent ion scans of the flavonoids yielded [M-H]-, except for catechol containing flavonoids, which were detected as borate adducts. These adducts can be used diagnostically to determine the presence or absence of catechol groups on unknown polyphenolic compounds. Product ion scans of the flavonoid glycosides and borate adducts typically yielded the deprotonated aglycone fragment as the base peak, which could be used to confirm the base structure of the flavonoid. This method's utility was demonstrated by analyzing flavonoids present in ethanolic extracts of Ginkgo biloba herbal supplements.

Capillary Electrophoresis in Wine Science

Capillary electrophoresis appeared to be a powerful and reliable technique to analyze the diversity of wine compounds. Wine presents a great variety of natural chemicals coming from the grape berry extraction and the fermentation processes. The first and more abundant after water, ethanol has been quantified in wines via capillary electrophoresis. Other families like organic acids, neutral and acid sugars, polyphenols, amines, thiols, vitamins, and soluble proteins are electrophoretically separated from the complex matrix.Here, we will focus on the different methodologies that have been employed to conduct properly capillary electrophoresis in wine analysis.Two examples informing on wine chemistry obtained by capillary electrophoresis will be detailed. They concern polyphenol analysis and protein profiling. The first category is a well-developed quantitative approach important for the quality and the antioxidant properties conferred to wine. The second aspect involves more research aspects dealing with microbiota infections in the vineyard or in the grape as well as enological practices.

Flavonoid profiles of three Bupleurum species and in vitro hepatoprotective of activity Bupleurum flavum Forsk

Background:

Bupleurum L. (Aspiaceae) species are used as herbal remedy in Chinese traditional medicine.

Objective:

The aim was to investigate the flavonoids in three annual European Bupleurum species, including B. baldense, B. affine and B. flavum, and to test their antioxidant and possible hepatoprotective effects.

Materials and Methods:

Flavonoids from the methanol-aqueous extracts were quantified by solid-phase extraction-high-performance liquid chromatography. Bupleurum extracts (1–220 mg/ml) were tested for their antioxidant activity in DPPH and ABTS assays, as well as on isolated liver rat microsomes. In vitro hepatoprotective activity of B. flavum flavonoid (BFF) mixture and rutin, and narcissin, isolated from the same mixture, were evaluated on carbon tetrachloride (CCl₄) and tert-butyl hydroperoxide (t-BuOOH) toxicity models in isolated rat hepatocytes.

Results:

Narcissin was the dominant flavonol glycoside in B. flavum being present at 24.21 ± 0.19 mg/g, whilst the highest content of rutin (28.63 ± 1.57 mg/g) was found in B. baldense. B. flavum possessed the strongest DPPH (IC₅₀ 22.12 μg/ml) and ABTS (IC₅₀ 118.15 μg/ml) activity. At a concentration 1 mg/ml of BFF (rutin 197.58 mg/g, narcissin 75.74 mg/g), a stronger antioxidant effect in microsomes was evidenced in comparison with silymarin, rutin and narcissin. The hepatoprotective effect of BFF significantly reduced the elevated levels of lactate dehydrogenase and malondialdehyde, and ameliorated glutathione, being most active in t-BuOOH-induced injury model when compared with CCl₄ toxicity (P < 0.001).

Conclusion:

In BFF, synergism of rutin and narcissin could be responsible for stronger protection against mitochondrial induced oxidative stress.

Separation/preconcentration and determination of quercetin in food samples by dispersive liquid-liquid microextraction based on solidification of floating organic drop -flow injection spectrophotometry

A new dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFOD)-flow injection spectrophotometry (FI) method for the separation and preconcentration of trace amounts of quercetin was developed. 1-Undecanol and methanol was used as the extraction and disperser solvent, respectively. The factors influencing the extraction by DLLME-SFOD such as the volume of the extraction and disperser solvents, pH and concentration of salt were optimized. The optimal conditions were found to be; volume of the extraction solvent, 80 μL; the volume of the disperser solvent, 100 μL; and the pH of the sample, 3. The linear dynamic range and detection limit were 5.0 × 10(-8)-5.0 × 10(-7) mol L(-1) and 1 × 10(-8) mol L(-1), respectively. The relative standard deviation (R.S.D.) at 6.1 × 10(-8) mol L(-1) level of quercetin (n = 10) was found to be 2.8 %. The method was successfully applied to the determination of quercetin in the apple, grape, onion and tomato samples. Figureᅟ

Quantification of individual phenolic compounds' contribution to antioxidant capacity in apple: a novel analytical tool based on liquid chromatography with diode array, electrochemical, and charged aerosol detection

Phenolics, particularly from apples, hold great interest because of their antioxidant properties. In the present study, the total antioxidant capacity of different apple extracts obtained by pressurized hot water extraction (PHWE) was determined by cyclic voltammetry (CV), which was compared with the conventional antioxidant assays. To measure the antioxidant capacity of individual antioxidants present in apple extracts, a novel method was developed based on high-performance liquid chromatography (HPLC) with photodiode array (DAD), electrochemical (ECD), and charged aerosol (CAD) detection. HPLC-DAD-ECD-CAD enabled rapid, qualitative, and quantitative determination of antioxidants in the apple extracts. The main advantage of using CAD was that this detector enabled quantification of a large number of phenolics using only a few standards. The results showed that phenolic acids and flavonols were mainly responsible for the total antioxidant capacity of apple extracts. In addition, protocatechuic acid, chlorogenic acid, hyperoside, an unidentified phenolic acid, and a quercetin derivative presented the highest antioxidant capacities.

Magnetic solid-phase extraction based on Fe3O4nanoparticle retrieval of chitosan for the determination of flavonoids in biological samples coupled with high performance liquid chromatography

Schemes of two-step magnetic retrieval of chitosan and its application as MSPE adsorbents for simultaneous extraction and preconcentration of targeted analytes in urine and serum samples.

Application of hot platinum microelectrodes for determination of flavonoids in flow injection analysis and capillary electrophoresis

The determination of quercetin and rutin by flow injection analysis (FIA) and capillary electrophoresis (CE) using electrochemical detection was described. These flavonoids were determined at normal (unheated) and hot platinum microelectrodes using cyclic voltammetry. When quercetin or rutin is reaching the platinum electrode, a change of the current in the region of the platinum oxide formation is observed. Integration of the current changes in this in this region creates analytical signals in the form of peaks. An increase of temperature to about 76°C in a small zone adjacent to the microelectrode causes an increase of the analytical signal by more than 6 times under FIA conditions. This method enables the use of hot microelectrodes as detectors in HPLC or CE. In CE the improvement of the analytical signal at hot microelectrodes is smaller than in FIA and increase only 1.3-3.4 times. Heated microelectrodes were used for analysis of the flavonoids in natural samples of the plant (extract of sea buckthorn) and a pharmaceutical preparation (Cerutin).

Analytical characterization of wine and its precursors by capillary electrophoresis

The accurate determination of marker chemical species in grape, musts, and wines presents a unique analytical challenge with high impact on diverse areas of knowledge such as health, plant physiology, and economy. Capillary electromigration techniques have emerged as a powerful tool, allowing the separation and identification of highly polar compounds that cannot be easily separated by traditional HPLC methods, providing complementary information and permitting the simultaneous analysis of analytes with different nature in a single run. The main advantage of CE over traditional methods for wine analysis is that in most cases samples require no treatment other than filtration. The purpose of this article is to present a revision on capillary electromigration methods applied to the analysis of wine and its precursors over the last decade. The current state of the art of the topic is evaluated, with special emphasis on the natural compounds that have allowed wine to be considered as a functional food. The most representative revised compounds are phenolic compounds, amino acids, proteins, elemental species, mycotoxins, and organic acids. Finally, a discussion on future trends of the role of capillary electrophoresis in the field of analytical characterization of wines for routine analysis, wine classification, as well as multidisciplinary aspects of the so-called "from soil to glass" chain is presented.

Determination of polyphenols in Spanish wines by capillary zone electrophoresis. Application to wine characterization by using chemometrics

A capillary zone electrophoresis (CZE) method for the simultaneous determination of 20 polyphenols in wine was developed. The separation was performed using fused-silica capillaries of 75 μm i.d. and a 30 mM sodium tretraborate buffer solution at pH 9.2 with 5% isopropanol as a background electrolyte. A capillary voltage of +25 kV with pressure-assisted (3.5 kPa) separation from minute 18 was applied, thus achieving a total analysis time of <25 min. Instrumental quality parameters such as limits of detection (LOD, values between 0.3 and 2.6 mg/L), linearity (r(2) > 0.990), and run-to-run and day-to-day precisions (RSD values lower than 6.5 and 15.7%, respectively) were established. Three different calibration procedures were evaluated for polyphenol quantitation in wines: external calibration using standards prepared in Milli-Q water, standard addition, and pseudomatrix-matched calibration using wine as a matrix. For a 95% confidence level, no statistical differences were observed, in general, between the three calibration methods (p values between 0.11 and 0.84), whereas for some specific polyphenols, such as cinnamic acid, syringic acid, and gallic acid, results were not comparable when external calibration was used. The CZE method using pseudomatrix-matched calibration was then proposed and applied to the analysis of polyphenols in 49 Spanish wines, showing satisfactory results and a wide compositional variation between wines. Electrophoretic profiles and other compositional data (e.g., peak areas of selected peaks) were considered as fingerprints of wines to be used for characterization and classification purposes. The corresponding data were analyzed by principal component analysis (PCA) to extract information on the most significant features contributing to wine discrimination according to their origins. Results showed that a reasonable distribution of wines depending on the elaboration areas was found, tyrosol and gallic, protocatechuic, p-coumaric, and caffeic acids being some representative discriminant compounds.