Analysis of flavanone-7-O-glycosides in citrus juices by short-end capillary electrochromatography

The separation of the major flavanone-7-O-glycoside constituents of Citrus was carried out by isocratic reversed phase capillary electrochromatography using a 75 microm i.d. silica fused column packed with 5 microm ODS silica gel. In comparison to HPLC mode, capillary electrochromatography resolution of flavanone glycosides was obtained with a high selectivity factor. Optimum separation conditions were found using a mixture of ammonium formate (pH 2.5)--acetonitrile (8:2, v/v) as the mobile phase by the short-end injection mode. Under these conditions all the investigated flavanones were baseline-resolved within short analysis time (i.e. between 5 and 10 min). A study, evaluating the intra- and inter-day repeatability as well as limit of detection and method linearity, was developed in accordance with the analytical procedures for method validation. The developed method was applied for the quantitative analysis of flavanone glycosides in commercial fruit juices (sweet orange, lemon and grapefruit).     

Gas chromatographic-mass spectrometric characterization of flavanones in citrus and grape juices.

A method for the characterization of flavanones in fruit juices, involving solvent extraction, hydrolysis to the corresponding aglycones, trimethylsilylation and combined gas chromatography-mass spectrometry, is reported. The application of the method is demonstrated for the analysis of orange, lemon, grapefruit and grape juices.     

Monosubstituted positively charged cyclodextrins: Synthesis and applications in chiral separation

Several series of novel structurally well-defined positively charged CDs, applicable to alpha-, beta- and gamma-CDs for chiral separation using CE and chromatographic techniques have been developed. The chiral resolution capabilities of different series CDs towards amino acids and anionic analytes in CE are systematically investigated by considering all separation parameters including CD type, alkyl chain length of the cations attached to the CD rim, CD concentration, buffer pH, separation temperature and organic solvent. Typical results are demonstrated in the context. Examples of chiral separation with HPLC and supercritical fluid chromatography are first demonstrated by using coated chiral stationary phases (CSPs). Optimum CD loading content on the coated CSPs was explored in the chiral separation of neutral analytes.     

Multidimensional liquid chromatography for the determination of chiral coumarins and furocoumarins in Citrus essential oils

In this work the enantiomeric distribution of chiral coumarins (meranzin and epoxyaurapten), and furocoumarins (oxypeucedanin, byakangelicol, and epoxybergamottin) in different Citrus essential oils (lemon, lime, grapefruit, and bitter orange) was determined by means of a heart-cutting multidimensional-liquid chromatography (MD-LC) system, equipped with a microsilica column in the first dimension in a combination to a cellulosic-based chiral column used in the second dimension. The normal phase-liquid chromatography-liquid chromatography (NP-LC-LC) instrumentation was equipped with a photodiode array detector and a multiport valve as interface. For method optimization and the determination of absolute configuration, natural compounds were isolated and racemic mixture was synthesized. The NP-LC-LC/PDA (where PDA is photodiode array) method provided a good baseline separation of chiral coumarins (meranzin and epoxyaurapten) and furocoumarins (epoxybergamottin and byakangelicol) present in cold-pressed Citrus essential oils without any sample pretreatment. Results obtained showed that for all the chiral compounds present in Citrus essential oils analyzed, there is always a clear prevalence of one of the two enantiomers, and do not appear influenced by the different geographical origin of the oils.     

Chiral Separations of Five Organic Catalysts by Cyclodextrin-modified Capillary Zone Electrophoresis

Chiral separation is very important and become a significant task of analytical chemistry in many fields. Capillary electrophoresis (CE) is a technique undergoing rapid development for chiral separation at the present time. With its high efficiency, simple operation, and extremely small sample volume,CE has become a powerful tool for chiral separation. There are many chiral selectors, such as cyclodextrins (CDs), proteins, chiral surfactants, antibiotics, bile salts, using in CE chiral separation. CDs has been most wildly used in them. Cyclodextrin (CD) is a cyclic sugar made of certain glucose units in which each has 5 chiral centers and it shows the shape of cavity with a big end and a small end. The inside of CD is hydrophobic and the outside is hydrophilic. The chiral selectivity of CD comes from the formation of host-guest compound between CD and analytes. The differences of the hydrogen-bond and the other interactions between CD and two enantiomers cause enantio-selectivity.     

A Standardized Extract Prepared from Red Orange and Lemon Wastes Blocks High-Fat Diet-Induced Hyperglycemia and Hyperlipidemia in Mice

Citrus fruits are a rich source of high-value bioactive compounds and their consumption has been associated with beneficial effects on human health. Red (blood) oranges (Citrus sinensis L. Osbeck) are particularly rich in anthocyanins (95% of which are represented by cyanidin-3-glucoside and cyanidin-3-6″-malonyl-glucoside), flavanones (hesperidin, narirutin, and didymin), and hydroxycinnamic acids (caffeic acid, coumaric acid, sinapic, and ferulic acid). Lemon fruit (Citrus limon) is also rich in flavanones (eriocitrin, hesperidin, and diosmin) and other polyphenols. All of these compounds are believed to play a very important role as dietary antioxidants due to their ability to scavenge free radicals. A standardized powder extract, red orange and lemon extract (RLE), was obtained by properly mixing anthocyanins and other polyphenols recovered from red orange processing waste with eriocitrin and other flavanones recovered from lemon peel by a patented extraction process. RLE was used for in vivo assays aimed at testing a potential beneficial effect on glucose and lipid metabolism. In vivo experiments performed on male CD1 mice fed with a high-fat diet showed that an 8-week treatment with RLE was able to induce a significant reduction in glucose, cholesterol and triglycerides levels in the blood, with positive effects on regulation of hyperglycemia and lipid metabolism, thus suggesting a potential use of this new phytoextract for nutraceutical purposes.     

Study of the enantioseparation capability of chiral dual system based on chondroitin sulfate C in CE

It has been reported that chiral dual system is able to improve the enantioseparation of enantiomers in many cases. Currently, the dual systems involved in CE chiral separation are mostly dual CDs systems, and the polysaccharides‐based chiral dual system was reported in only one paper. To the best of our knowledge, the use of chondroitin sulfate C (CSC)‐based dual system for enantiomeric separation has not been reported previously. Herein, four CSC‐based chiral dual systems, namely CSC/glycogen, CSC/chondroitin sulfate A (CSA), CSC/hydroxypropyl‐β‐CD (HP‐β‐CD), as well as CSC/β‐CD (β‐CD), were evaluated for the first time for their enantioseparation capability by CE in this paper. During the course of the work, the influences of chiral selector concentration and buffer pH values on enantioseparation in dual systems were systematically investigated. Under the optimized conditions, the dual system consisting of CSC and glycogen exhibited better separations toward nefopam, duloxetine, sulconazole, atenolol, laudanosine, and cetirizine enantiomers compared to the single CSC or glycogen system. The combination of CSC and HP‐β‐CD improved the separation of amlodipine and chlorphenamine enantiomers. However, no synergistic effect was observed in the CSC/CSA and CSC/β‐CD systems.     

Separation of brombuterol enantiomers in capillary electrophoresis with cyclodextrin‐type chiral selectors and investigation of structure of selector‐selectand complexes using nuclear magnetic resonance spectroscopy

The major goal of this study was to determine the affinity pattern of brombuterol (BB) enantiomers toward various cyclodextrins (CD) and to evaluate the potential of NMR spectroscopy for understanding fine mechanisms of interactions between CDs and BB enantiomers. Separation of BB enantiomers was performed in a fused‐silica capillary using a phosphate buffer, pH 2.5, at the room temperature in the normal polarity mode. It was shown once again that CE in combination with NMR spectroscopy represents a very sensitive tool for studies of affinity patterns and structure of CD complexes with chiral guests. Although opposite affinity patterns of BB enantiomers were observed toward native β‐ and γ‐CDs, no significant differences between the structures of the complexes of these two CDs with BB were detected by NMR spectroscopy. In contrary to this, the opposite affinity pattern of BB enantiomers toward β‐CD and its two sulfated derivatives, heptakis (2,3‐O‐diacetyl‐6‐sulfo)‐β‐CD (HDAS‐β‐CD) and heptakis (2‐O‐methyl‐3,6‐di‐O‐sulfo)‐β‐CD (HMDS‐β‐CD) was associated with major differences in the structure of the complexes. In addition, it was shown again that HMDS‐β‐CD provides separation of enantiomers without formation of inclusion‐type complex with the chiral analyte.     

Spectrophotometric determination of vitamin C in citrus fruits using peri-naphthindan-2,3,4-trione

Analytical and Bioanalytical Chemistry - A spectrophotometric method for the determination of vitamin C in lemon, orange, and grapefruit juices is described. It is based on the reaction with...     

Enantiomeric separation of enzymatic hydrolysis products of dihydropyrimidinone methyl ester with cationic cyclodextrin by capillary electrophoresis

The achiral separation of dihydropyrimidinone (DHP) methyl ester and its corresponding carboxylic acid and the chiral separation of their respective enantiomers were achieved in a single analysis using capillary electrophoresis (CE) with quaternary ammonium-beta-cyclodextrin (QA-beta-CD) as a chiral buffer additive. Separation of the DHP methyl ester from the corresponding carboxylic acid was achieved because the acid was negatively charged at pH 8.3 of the running buffer and the ester is neutral. Upon the addition of QA-beta-CD, the enantiomers of the acid and ester were well resolved before and after the electroosmotic flow, respectively. In addition, the minor DHP methyl ester enantiomer (R isomer) was well separated from several impurities. This CE system was used to monitor the progress of a bioresolution reaction that utilizes an enzyme to convert the R isomer of the ester to its corresponding acid. The quantities of all four enantiomers can be determined using a single set of CE conditions. In addition, it is demonstrated that samples can be directly injected into the capillary without sample pretreatment due to the fact that the coating of the cationic CD on the capillary surface prevents adsorption of the positively charged enzyme. The effects of other experimental parameters such as type of CDs, concentration of CDs, pH, temperature, and the preconditioning of capillary were also studied.     

Determination of flavonoids in citrus juices by micro-HPLC-ESI/MS

Flavonoids are a large class of naturally occurring aromatic secondary plant metabolites. They constitute one of the most characteristic classes found in nature and more than 4000 flavonoids have been identified and divided into several subclasses. Flavonoids have several effects on human health, mainly related to their antioxidant activity. As a result of the increased interest in the biologically active compounds in food, many research studies have investigated the detection and quantification of antioxidants. Citrus plants are of great interest since they accumulate large amounts of flavonoids and fruit and juices of these species are consumed in large quantities. Despite the extensive research performed on Citrus flavonoids, many compounds still remain unidentified. In this work, flavonoids of five citrus juices: lemon, grapefruit, bergamot, orange, and mandarin were analyzed by microHPLC coupled on-line with an MS detector equipped with an ESI source operating in negative mode. The use of microcolumn HPLC greatly enhanced detection performance. In total, 20 flavonoids of two different subclasses (flavanone and flavone glycosides) were identified with the help of retention data and MS spectral information.     

卡替诺尔和氟西汀对映体的高效毛细管电泳分离

考察了以羧甲基－β－（环糊精－β－CD）、β－环糊清（β－CD）、羟丙基－β－环糊精（HP－β－CD）、二甲基－β－环糊精（DM－β－CD)为手性选择剂,在50mmol/L醋酸三乙胺缓冲溶液中分离卡替诺尔和氟西汀对映体。该文还通过考察手性选择剂的浓度、背景电解质的酸度、背景电解质的类型等因素对映体手性分离的影响,对分离条件进行了优化,初步探讨了手性识别机理。实验结果表明：用约4mmol/L的CM－β－CD分离氟西汀和卡替诺尔对映体,能使对映体达到良好分离,不仅节约了分析成本,也简化了分析过程。     

Simultaneous determination of sorbic and benzoic acids in commercial juices using the PLS-2 multivariate calibration method and validation by high performance liquid chromatography

A new method to determine a mixture for preserving sorbic and benzoic acids in commercial juices is proposed. The PLS-2 model was obtained preparing 40 standard solutions adding concentration of sorbic and benzoic acid to filtered natural juices of apple, lemon, orange and grapefruit. The concentration of analytes in the commercial samples was evaluated using the obtained model by UV spectral data. The PLS-2 method was validated by high performance liquid chromatography (HPLC), finding a relative error less than 12% between the PLS-2 and HPLC methods in all cases.     

Enantioseparation of α-Amino Acids by Capillary Electrophoresis Using L-Cysteine-Modified Cyclodextrins as Chiral Selectors

Capillary electrophoresis (CE) is a powerful separation technique that was used in a wide range of analytical chemical applications. Cyclodextrins(CDs) are the most commonly used chiral selectors in chiral capillary electrophoresis at the present time. Under neutral conditions, however, native CDs are neutral and usually applicable only for the enantioseparation of charged analyses. To overcome this defect we modified α- and β-CD with a L-cysteine moiety and used the CD derivatives as chiral selectors for the separation of a-amino acid enantiomers by the ligand exchange mode.     

Bioflavonoid profile of citrus juices from Greece

High‐performance liquid chromatography with confirmation by UV–visible photodiode array detector–positive electrospray ionization–mass spectrometry [HPLC‐UV–vis‐DAD‐(+ESI)‐MS] with enhanced fragmentation by appropriate adjustment of the cone voltage was used to determine bioflavonoid content of five citrus species (tangerine, sanguine, sour orange, lemon and grapefruit) cultivated in Greece which come from citrus varieties analyzed for the first time. The main groups of bioflavonoids found in the juice of the citrus species according to HPLC retention times, spectral data and literature references were O‐glycosylated flavanones and flavones, C‐glucosylated flavones, O‐glucosylated flavones, O‐C‐glucosylated flavones like saponarin and a phenolic derivative. Copyright © 2012 John Wiley & Sons, Ltd.     

Racemization at C-2 of naringin in pummelo (Citrus grandis) with increasing maturity determined by chiral high-performance liquid chromatography

The relative content of (2S)- and (2R)-naringin in the albedo of pummelo during maturation in the entire season was determined by normal-phase HPLC using Chiralpak IB, a polysaccharide-derived chiral stationary phase, and n-hexane/ethanol doped with 0.5% TFA as mobile phase. A sigmoid curve was obtained showing variation from 95.3% of (2S)-naringin in very immature fruits to 53% in mature fruit samples (2.3 and 14.4 cm diameter, respectively). A comparison was made with previous results obtained for grapefruit and sour orange and a tentative explanation of the bitter taste of sour orange is proposed. The Chiralpak IB is much more efficient with respect to the Chiralcel OD used for the other two Citrus species and separation and resolution factors of 1.73 and 9.2, respectively, were achieved. Authentic samples of naringin and neohesperidin were also separated into their C-2 diastereomers with Chiralpak IB and isolation of the pure diastereomers of naringin was accomplished.     

Modeling and optimization of the chiral selectivity of basic analytes in chiral capillary electrophoresis with negatively charged cyclodextrins using electrochemical detection

A mathematical model concerning the separation selectivity of basic analytes in chiral capillary electrophoresis (CE) modified with negatively charged cyclodextrins (CDs) has been presented to describe the dependence of chiral selectivity on the buffer pH and the chiral selector concentration. The electrophoretic method to determine the parameters of the model has also been developed. The model has been tested with racemic epinephrine and isoproterenol as target analytes and sulfonated beta-CD as chiral selector. The agreements have been found between the calculated and the measured values. Some significant conclusions to optimize chiral CE separation have been derived from the model and proven by the experiments. Electrochemical detection was used to meet the requirement of the low introduced concentration of analytes.     

The Use of Dual Cyclodextrin Chiral Selector Systems in the Enantioseparation of Pharmaceuticals by Capillary Electrophoresis: An Overview

Cyclodextrin (CD) derivatives are the most efficient and frequently used chiral selectors (CSs) in capillary electrophoresis (CE). There are situations when the use of a single CD as CS is not enough to obtain efficient chiral discrimination of the enantiomers; in these cases, sometimes this problem can be resolved using a dual CD system. The use of dual CD systems can often dramatically enhance enantioseparation selectivity and can be applied for the separation of many analytes of pharmaceutical interest for which enantioseparation by CE with another CS systems can be problematic. Usually in a dual CD system an anionic CD is used together with a neutral one, but there are situations when the use of a cationic CD with a neutral one or the use of two neutral CDs or even two ionized CDs can be an efficient solution. In the current review we present general aspects of the use of dual CD systems in the analysis of pharmaceutical substances. Several examples of applications of the use of dual CD systems in the analysis of pharmaceuticals are selected and discussed. Theoretical aspects regarding the separation of enantiomers through simultaneous interaction with the two CSs are also explained. Finally, advantages, disadvantages, potential and new direction in this chiral analysis field are highlighted.     

Enantioseparation of thalidomide and its hydroxylated metabolites using capillary electrophoresis with various cyclodextrins and their combinations as chiral buffer additives.

The separation of thalidomide (TD) and its hydroxylated metabolites including their simultaneous enantioseparation was studied in capillary electrophoresis (CE) using four different randomly substituted charged cyclodextrin (CD) derivatives, the combinations of some of them with each other, and beta-CD. TD, as well as two metabolites recently found in incubations of human liver microsomes and human blood, 5-hydroxythalidomide (5-OH-TD) and one of the diastereomeric 5'-hydroxythalidomides (5'-OH-TD), are neutral compounds. Therefore, they were resolved using charged chiral selectors in CE. Two different separation modes (normal polarity and carrier mode) and two different capillaries (fused-silica and polyacrylamide-coated) were tested. Based on the behavior of the individual CDs, their designed combinations were selected in order to improve the separation selectivity and enantioselectivity. Under optimized conditions all three chiral compounds and their enantiomers were resolved simultaneously.     

Characterization of yeast strains for wine production

Sixteen yeast strains isolated from grapefruit (Citrus paradis), orange (Citrus sinensis) and pineapple (Ananas comosus) were characterized using standard microbiological procedures. The species were identified as Saccharomyces uvarum, S. cerevisiae, S. carlbergensis, and S. ellipsoideus. Their abilities for wine production were tested by using sugar and ethanol tolerance tests. The best biochemically active strain, S. ellipsoideus, was used along with commercially available baker's yeast (S. cerevisiae) to produce wine from grapefruit, orange, and pineapple juices. After fermentation for 14 d with S. cerevisiae and 21 d with S. ellipsoideus, wines produced were compared with Baron de Valls (standard). The highest (10.47% [v/v]) and lowest (7.68% [v/v]) alcohol concentrations with corresponding residual sugar concentrations of 1.88% (w/v) and 7.7% (w/v) were produced from orange after fermentation with S. cerevisiae and S. ellipsoideus, respectively. S. ellipsoideus was found to be the best yeast strain producing wine with the highest acceptable score of 7.41 from orange. The study revealed the possibility of producing wine from our locally available fruits using simple, cheap, and adaptable technology with biochemically characterized yeast strains.