Quantitative and qualitative analysis of flavonoid markers in Frucus aurantii of different geographical origin by capillary electrophoresis with electrochemical detection

Development and validation of ultra-high performance supercritical fluid chromatography method for quantitative determination of four target flavonoids components in citrus samples

A new method for the analysis of four target flavonoids in two kinds of citrus samples by ultra-high performance supercritical fluid chromatography (UHPSFC) method was developed. Main variables affecting the UHPSFC separation were optimized, and under the optimized conditions the four target compounds (tangeretin, nobiletin, hesperetin and naringenin) can be separated within 10 min. The UHPSFC method allowed the determination of the four target compounds in the diluted stock solutions with limit of detection (LOD) ranging from 1.08 to 2.28 μg mL−1, and limit of quantification (LOQ) ranging from 1.45 to 4.52 μg mL−1, respectively. The coefficients of determination (R 2) of the calibration curves were higher than 0.9950. The recoveries of the four target compounds at three different concentrations were in the range of 82.4–117.6%. The validation results demonstrated that the proposed method is simple, accurate, time-saving and environment friendly, and it is applicable to a variety of complex samples such as medicine-food dual purpose herbs and functional foods.

A Targeted Metabolomics Approach to Study Secondary Metabolites and Antioxidant Activity in 'Kinnow Mandarin' during Advanced Fruit Maturity

In this study, we investigated the impact of harvest maturity stages and contrasting growing climates on secondary metabolites in Kinnow mandarin. Fruit samples were harvested at six harvest maturity stages (M1−M6) from two distinct growing locations falling under subtropical−arid (STA) and subtropical−humid (STH) climates. A high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) technique was employed to identify and quantify secondary metabolites in the fruit juice. A total of 31 polyphenolics and 4 limonoids, with significant differences (p < 0.05) in their concentration, were determined. With advancing maturity, phenolic acids and antioxidant activity were found to increase, whereas flavonoids and limonoids decreased in concentration. There was a transient increase in the concentration of some polyphenolics such as hesperidin, naringin, narirutin, naringenin, neoeriocitrin, rutin, nobiletin and tangeretin, and limonoid aglycones such as limonin and nomilin at mid-maturity stage (M3) which coincided with prevailing low temperature and frost events at growing locations. A higher concentration of limonin and polyphenolics was observed for fruit grown under STH climates in comparison to those grown under STA climates. The data indicate that fruit metabolism during advanced stages of maturation under distinct climatic conditions is fundamental to the flavor, nutrition and processing quality of Kinnow mandarin. This information can help in understanding the optimum maturity stage and preferable climate to source fruits with maximum functional compounds, less bitterness and high consumer acceptability.

From the Field to the Bottle—An Integrated Strategy for Wine Authenticity

The wine sector is one of the most economically important agro-food businesses. The wine market value is largely associated to terroir, in some cases resulting in highly expensive wines that attract fraudulent practices. The existent wine traceability system has some limitations that can be overcome with the development of new technological approaches that can tackle this problem with several means. This review aims to call attention to the problem and to present several strategies that can assure a more reliable and authentic wine system, identifying existent technologies developed for the sector, which can be incorporated into the current traceability system.

Highly sensitive detection of hesperidin using AuNPs/rGO modified glassy carbon electrode

The highly sensitive and selective electrochemical sensor of hesperidin based on gold nanoparticles (AuNPs) and reduced graphene oxide (rGO) modified glassy carbon electrode (GCE) is reported.

Evaluation of chemical components in Citri Reticulatae Pericarpium of different cultivars collected from different regions by GC-MS and HPLC

To discriminate the feasible differences and find potential similarities and relationships of Citri Reticulatae Pericarpium (CRP), this work was accomplished by a comprehensive and reliable method using gas chromatography–mass spectrometer (GC–MS) to analyze the volatile oils and high‐performance liquid chromatography (HPLC) simultaneously to determine the contents of five bioactive flavonoids, namely hesperidin, nobiletin, 3,5,6,7,8,3′,4′‐heptamethoxyflavone, tangeretin, and 5‐hydroxy‐6,7,8,3′,4′‐pentamethoxyflavone in 25 batches of CRP samples of 10 cultivars collected from different regions in China. The GC–MS analyses indicated that 98 compounds were successfully identified from the volatile oils obtained and the major constituents of volatile oil are d‐limonene, γ‐terpinene, α‐pinene, linalool, and myrcene. Even 2‐(methylamino) benzoate was found in all cultivar samples harvested at maturation stage. Under the optimal condition, the quantitative analyses of five bioactive flavonoids were successfully performed by HPLC and hierarchical cluster analysis (HCA). Results showed significant differences among cultivars in the contents of five bioactive flavonoids mentioned earlier. The HCA and GC–MS results provided a convenient approach which might be applied for rapid similarity evaluation and also holds the potential for analysis of compounds present in other plants. Therefore, this work obtained offers scientific basis to control quality and develop medicinal value of the medicinal materials in CRP.

Simultaneous Quantification of Seven Bioactive Flavonoids in Citri Reticulatae Pericarpium by Ultra-Fast Liquid Chromatography Coupled with Tandem Mass Spectrometry

INTRODUCTION

Citri Reticulatae Pericarpium (CRP) is a commonly-used traditional Chinese medicine with flavonoids as the major bioactive components. Nevertheless, the contents of the flavonoids in CRP of different sources may significantly vary affecting their therapeutic effects. Thus, the setting up of a reliable and comprehensive quality assessment method for flavonoids in CRP is necessary.

OBJECTIVE

To set up a rapid and sensitive ultra-fast liquid chromatography coupled with tandem mass spectrometry (UFLC-MS/MS) method for simultaneous quantification of seven bioactive flavonoids in CRP.

METHODS

A UFLC-MS/MS method coupled to ultrasound-assisted extraction was developed for simultaneous separation and quantification of seven flavonoids including hesperidin, neohesperidin, naringin, narirutin, tangeretin, nobiletin and sinensetin in 16 batches of CRP samples from different sources in China.

RESULTS

The established method showed good linearity for all analytes with correlation coefficient (R) over 0.9980, together with satisfactory accuracy, precision and reproducibility. Furthermore, the recoveries at the three spiked levels were higher than 89.71% with relative standard deviations (RSDs) lower than 5.19%. The results indicated that the contents of seven bioactive flavonoids in CRP varied significantly among different sources. Among the samples under study, hesperidin showed the highest contents in 16 samples ranged from 27.50 to 86.30 mg/g, the contents of hesperidin in CRP-15 and CRP-9 were 27.50 and 86.30 mg/g, respectively, while, the amount of narirutin was too low to be measured in some samples.

CONCLUSION

This study revealed that the developed UFLC-MS/MS method was simple, sensitive and reliable for simultaneous quantification of multi-components in CRP with potential perspective for quality control of complex matrices. Copyright © 2016 John Wiley & Sons, Ltd.

Separation and determination of flavonoids in three traditional chinese medicines by capillary electrophoresis with amperometric detection

Flavonoids are important active ingredients in many traditional Chinese medicines. In this paper, capillary electrophoresis with amperometric detection was employed to separate and detect eight flavonoids, rutin, quercetrin, quercetin, kaempferol, kaempferide, catechin, apigenin, and luteolin, in a home-made capillary electrophoresis device. Under the separation voltage of 2000 V, the eight flavonoids could be completely separated within 33 min in 18 mM borax running buffer at pH 10.2. Good linear relationships were obtained for all analytes and the detection limits for flavonoids ranged from 0.46 to 0.85 μM. Then, the method was applied to separate and determine the flavonoids in three traditional Chinese medicines, hippophae rhamnoides, hypericum perforatum, and cacumen platycladi. Finally, rutin, kaempferol, quercetin, and quercetrin were discovered in these medicines and the concentrations ranged from 0.28 to 9.94 mg/g. The recoveries of flavonoids ranged from 84.7 to 113%, which showed the high reliability of this method.

High-performance liquid chromatographic analysis of biogenic amines in pharmaceutical products containing Citrus aurantium

A reverse-phase (RP)-HPLC method is reported for determining L-tyrosine, p-octopamine, synephrine, tyramine and hordenine as chemical markers of the species Citrus aurantium in raw material, dry extracts and phytotherapeutic herbal formulations. Using RP-HPLC with diode array detection (DAD) and gradient elution, the amines were determined in 12 different products from different Brazilian states labelled as containing C. aurantium. The presence of the amines was confirmed by mass spectrometry using electrospray ionisation (ESI-MS/MS). This RP-HPLC method allowed the separation of the amines from complex mixtures containing caffeine, ephedrine, salicin and other raw materials (e.g. Garcinia camboja, Phaseolus vulgaris, Caralluma fimbriata, Cassia nomane, Ephedra sp. and Cordia ecalyculata). The method proved useful and selective for inspecting herbal medicines containing p-synephrine and structural analogues. The herbal products analysed had a p-synephrine content ranging from 0.005 to 4.0% (w/w).

Simultaneous determination of flavanones, hydroxycinnamic acids and alkaloids in citrus fruits by HPLC-DAD-ESI/MS

A simple and accurate method has been developed to simultaneously separate and determine 10 bioactive compounds in citrus fruits by high-performance liquid chromatography coupled with diode array detection and electrospray ionisation mass spectrometry (HPLC-DAD-ESI/MS). This HPLC assay was performed on a reversed-phase C18 column with acetonitrile and 0.1% (v/v) aqueous formic acid as mobile phase. DAD has been performed at 273, 283 and 324nm for quantification of the alkaloids, flavanones and hydroxycinnamic acids. MS was also employed to identify the each analyte. Ten analytes (naringin, hesperidin, neohesperidin, ferulic acid, p-coumaric acid, chlorogenic acid, caffeic acid, octopamine, synephrine and tyramine) demonstrated good linearity (r⩾0.9990) in a relatively wide concentration range. The method revealed high average recovery (range, 92.1-97.9%) and good precision with interday and intraday variations with less than 4.71%. The limits of detection (LODs) ranged from 0.02 to 0.11μg/ml, while the limits of quantification (LOQs) were defined in the range of 0.08-0.39μg/ml. The proposed method has been successfully applied to analyse three types of bioactive constituents in eight citrus hybrids pulps and eight citrus hybrids peels, which has been successfully cultivated in China.

Fast CE analysis of adrenergic amines in different parts of Citrus aurantium fruit and dietary supplements

A CE method has been developed for the simultaneous analysis of the adrenergic amines synephrine, octopamine and tyramine in Citrus aurantium (bitter orange) fruit extracts and in dietary supplements. The analytes were separated on a fused silica capillary (50 microm id, 40.0 cm effective length, 48.5 cm total length) using a BGE composed of phosphate buffer (pH 2.5, 50 mM) and applying a 30 kV potential. The samples were injected hydrodynamically at 50 mbar for 25 s. The use of photodiode array detection (lambda=195 nm) allowed the quantification of the analytes and the control of peak purity. The method has been fully validated, obtaining satisfactory values of precision and extraction yield. The analytes are extracted with water from the dried whole fruits or fruit parts (endocarp, mesocarp and exocarp) or from the commercial formulations and directly injected into the CE apparatus. The results obtained were satisfactory in terms of precision (RSD < 5.7%) and accuracy (recovery > 89%). Thus, the method has demonstrated to be suitable for the qualitative and quantitative determination of synephrine, octopamine and tyramine in C. aurantium extracts, for dietary supplement quality control and for food adulteration identification.

Simultaneous determination of five bioactive flavonoids in pericarpium Citri reticulatae from china by high-performance liquid chromatography with dual wavelength detection

To evaluate the quality of Pericarpium Citri Reticulatae from China, a new, simple, and accurate method involving high-performance liquid chromatography with dual wavelength detection was developed for the simultaneous determination of five bioactive flavonoids, hesperidin, nobiletin, 3,5,6,7,8,3',4'-heptamethoxyflavone, tangeretin, and 5-hydroxy-6,7,8,3',4'-pentamethoxyflavone for the first time. Under the optimal condition, analysis was performed on a Dikma Diamonsil C(18) column and gradient elution with a solvent system of acetonitrile and water at a flow rate of 1.0 mL/min and detected at 283 and 330 nm, respectively. All five calibration curves exhibited good linearity (R2 > 0.9997). The relative standard deviation values for intra- and interday precision were less than 5% with accuracies between 95.16% and 104.71%. The recoveries were in the range of 96.91-103.20%. The established method was successfully applied to determine above five flavonoids in 32 samples collected from different districts of China, and the results demonstrated that the method may be used as strong research tools for quality control of Pericarpium Citri Reticulatae and chemotaxonomic investigation in botanical sciences of Citrus species.

Extraction, separation, and detection methods for phenolic acids and flavonoids

The impetus for developing analytical methods for phenolic compounds in natural products has proved to be multifaceted. Hundreds of publications on the analysis of this category of compounds have appeared over the past two decades. Traditional and more advanced techniques have come to prominence for sample preparation, separation, detection, and identification. This review provides an updated and extensive overview of methods and their applications in natural product matrices and samples of biological origin. In addition, it critically appraises recent developments and trends, and provides selected representative bibliographic examples.

Capillary electrophoresis coupled with electrochemical detection using porous etched joint for determination of antioxidants

Capillary electrophoresis coupled with electrochemical detection (CE-EC) for determination of antioxidants, propyl gallate (PG) and tert-butylhydroquinone (TBHQ), in cosmetic samples was proposed in this work. A porous etched joint was used to isolate the electrochemical detection from the electrophoretic high voltage. Compared with the 25 microm i.d. capillary without a decoupler in a CE-EC system, a 75 microm i.d. capillary applied in the present system gave an improvement in both sample injection and sensitivity. Moreover, the carbon fiber working electrode could be directly in touch with the end of separation capillary due to the elimination of the effect of separation voltage on the EC detection, so the alignment of working electrode and capillary became easy and the dead volume was also decreased. Baseline separation of the two antioxidants was achieved by CE in a 50 cm long x 75 microm i.d. capillary at 20 kV using 5.0 mmol L(-1) phosphate buffer (pH 8.00). 0.7 V (versus Ag/AgCl) was applied to the carbon fiber electrode for electrochemical detection. Under the optimal condition, the precisions (RSD, n=4) of peak height and migration time of PG and TBHQ were 2.39-3.59% and 0.34-0.44%, respectively. The detection limits of PG and TBHQ were 2.51x10(-6) and 4.88 x 10(-6) mol L(-1) for standard solution and 0.0751 and 0.0328 mg g(-1) for the real cosmetic samples with consumption of 0.3g sample. Analysis of TBHQ and PG in cosmetics samples was also achieved with the present system and the spiked recoveries of two analytes in cosmetics samples were in the range of 93.6-98.8%.

Comparison of two sample preconcentration strategies for the sensitivity enhancement of flavonoids found in Chinese herbal medicine in micellar electrokinetic chromatography with UV detection

Two on-column preconcentration techniques named stacking with reverse migrating micelles (SRMM) and anion selective electrokinetic injection and a water plug-sweeping with reverse migrating micelles (ASIW-sweep-RMM) were used and compared for concentration and separation of flavonoids in Chinese herbs using reverse migration micellar electrokinetic chromatography (RM-MEKC). The optimal background electrolyte (BGE) used for separation and preconcentration was a solution composed of 20mM phosphoric acid (H(3)PO(4))-100mM sodium dodecyl sulfate (SDS)-20% (v/v) acetonitrile (ACN) buffer (pH 2.0), the applied voltage was -15kV. To achieve reasonable results of the two techniques, the conditions which affected preconcentration were examined. A comparison of used techniques with normal hydrodynamic injection (5s), concerning enhancement factors and limits of detection (LODs) was presented. Under the optimum stacking conditions, about 27-37- and 45-194-fold improvement in the detection sensitivity was obtained for SRMM and ASIW-sweep-RMM, respectively, compared to usual hydrodynamic sample injection (5s). The LODs (S/N=3) for SRMM and ASIW-sweep-RMM in terms of peak height, can reach down to 1.15 x 10(-2) microg/ml for hesperetin and 2.4 x 10(-3) microg/ml for nobiletin, respectively. Finally, the amounts of the six flavonoids in extract of Fructus aurantii Immaturus were successfully determined using ASIW-sweep-RMM. The six analytes were baseline separated with sample matrix under the optimum ASIW-sweep-RMM conditions and the experimental results showed that preconcentration was well achieved after the dilution of sample solutions.

Flavonoid composition of Citrus juices

In the early nineties the presence of flavonoids in Citrus juices began to attract the attention of a number of researchers, as a result of their biological and physiological importance. This short review will explore two different aspects. The first part will focus on analytical techniques for the characterization of juices from different Citrus fruits regarding their flavonoid content (even if present in only trace amounts), concentrating on the most widely used methods (LC-MS and LC-MS-MS). The second part analyzes data reported in the literature regarding the composition of Citrus juices. The main components that have been detected so far are flavanone-O-glycosides and flavone-O- or -C-glycosides. The presence of such derivatives in various hand-squeezed and industrial juices is discussed, with special emphasis on their correlation to different species.

Simultaneous determination of flavonoid and alkaloid compounds in Citrus herbs by high-performance liquid chromatography-photodiode array detection-electrospray mass spectrometry

The major active biological constituents in Citrus herbs are flavonoids, especially hesperidin, naringin and alkaloids, mainly synephrine, with beneficial medical effects on human health. They are used as the markers to control the quality of Citrus herbs. In this paper, a new ion pairing chromatographic method was developed to exclude the most polar solute (synephrine) from the viod volume and to maintain selectivity between the two other solutes (hesperidin and naringin). Perfluorinated carboxylic acids, which are appropriate for MS detection due to their volatility, were used as ion-pairing agents. The problems of the synephrine separation, such as band tailing and low retention, were solved successfully by using perfluorinated carboxylic acids. The effect of heptafluorobutyric acid (HFBA) was the best in the three investigated perfluorinated carboxylic acids. For the flavanone glycosides, the influence of the perfluorinated acids on retention time was rather weak. The two different kinds of the analytes were separated satisfactorily in one run using an isocratic eluent and the total analysis time takes less than 10 min. The abundance of pseudomolecular ions was recorded using selected ion monitoring (SIM) mode of m/z 135.1, 273.1 and 303.1 for synephrine, naringin and hesperidin, respectively. The contents of hesperidin, naringin and synephrine in several Citrus herbs were simultaneously determined by the proposed method.

Rapid qualitative and quantitative analyses of flavanone aglycones in Fructus aurantii by HPLC ion-trap MS

IT-MS operated in the positive mode was applied for the rapid characterization/quantification of the flavanones in extracts from Fructus aurantii. APCI-MS and CID MS/MS provide unequivocal molecular weight (MW) data of these compounds and useful information about their structures (diagnostic fragment ions). Main fragment pathways include neutral losses of H2O, C2H2O, and B-ring as well as a retro-Diels-Alder (RDA) fragment giving rise to [1,3A + H], [1,3B+H]+, and [1,4B-H2 + H]+ ions, which form the characteristic MS/MS "fingerprint" of flavanone aglycones. When screening extracts of F. aurantii for flavanone aglycones, eight target compounds were characterized using this fingerprint. Meanwhile, ESI-MS in full-scan mode was developed and validated for the quantification of the main flavanone aglycones in F. aurantii. This method is simple, accurate, fast and requires only 16 min per sample for direct detection and quantification of naringenin and hesperetin. All the results and these characteristic fragments showed that the IT-MS is a powerful tool for the structural characterization and quantitative determination offlavanone aglycones.

Quality control and discrimination of pericarpium citri reticulatae and pericarpium citri reticulatae viride based on high-performance liquid chromatographic fingerprints and multivariate statistical analysis

High-performance liquid chromatographic (HPLC) fingerprints of pericarpium citri reticulatae (PCR) and pericarpium citri reticulatae viride (PCRV) were firstly measured for deliberately collected 39 authentic samples and 21 commercial samples. Both correlation coefficients of similarity for chromatograms and absolute peak areas of characteristic compounds were calculated for quantitative expression of the HPLC fingerprints. After principal component analysis (PCA) successfully distinguished the 'mixed peels' samples from authentic samples, partial least squares-linear discrimination analysis (PLS-LDA) was then effectively applied to class separation between authentic PCR and PCRV. Furthermore, the unequivocally determined compounds, hesperidin, nobiletin and tangeretin, were screened out by loadings plots of PCA and PLS-LDA. The results indicated that they could be used as chemical markers for discrimination among different groups of samples. The proposed method shows an efficient strategy for quality control of PCR and PCRV, which cannot only distinguish the 'mixed peels' but also discriminate authentic PCR and PCRV. This method has potential perspective for quality control of traditional Chinese medicine (TCM).

A new method for fabrication of an integrated indium tin oxide electrode on electrophoresis microchips with amperometric detection and its application for determination of synephrine and hesperidin in pericarpium citri reticulatae

A new, simple, and fast method to integrate indium tin oxide electrode in an amperometric detection (AD) microchip is introduced. Without the help of photoresist and complicated apparatus, the microchip could be fabricated in most laboratories in a very short time by this method. The experiment indicated that the microchip was stable and had good reproducibility. On this microchip, a new method was established to separate and determine synephrine and hesperidin, which are the main electroactively bioactive ingredients of pericarpium citri reticulatae, by AD. Under the optimal conditions, the two compounds could be completely separated within 5.5 min and the detection limits were 0.13 and 0.57 microg/mL, respectively. The proposed method has been successfully used to determine synephrine and hesperidin in real pericarpium citri reticulatae sample, and the results show that the proposed method is sensitive, reliable, fast, and economical.

A rapid and simple procedure for the determination of synephrine in dietary supplements by gas chromatography-mass spectrometry

A simple and rapid procedure based on gas chromatography-mass spectrometry (GC-MS) is described for determination of synephrine, active principle of Citrus aurantium plant, in solid and liquid dietary supplements. After the addition of 3,4-methylenedioxypropylamphetamine as internal standard (I.S.), a liquid-liquid extraction procedure in alkaline conditions with chloroform/isopropanol (9:1, v/v) was applied to the samples prior to analysis. Chromatography was performed on a fused capillary column and synephrine and I.S., derivatized with pentafluoropropionic anhydride, were determined in the selected-ion-monitoring (SIM) mode. The method was validated in the range 0.1-50 microg/mg or microg/mL synephrine. Mean recovery ranged between 89.3% and 90.5% in both solid and liquid dietary supplements. The quantification limit was 0.1 microg/mg or microg/ml. The method was applied to analysis of various dietary supplements promoted for aiding weight control containing, among other constituents such as ephedrine alkaloids and methylxanthines, Citrus aurantium. Amount of synephrine present in such products ranged from 3.1 microg/mg solid product to 480.2 microg/mL liquid product.