Biomedical subjects

Xingguo Chen

Publications and source records attributed to Xingguo Chen.

At least 55 records · Page 3Linked to original sources

PubMed2004

Binding of the bioactive component jatrorrhizine to human serum albumin.

The interaction between Jatrorrhizine with human serum albumin (HSA) were studied by fluorescence quenching technique, circular dichroism (CD) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Fluorescence data revealed the presence of a single class of binding site on HSA and its binding constants (K) are 7.278 x 10(4), 6.526 x 10(4), and 5.965 x 10(4) L.mol(-1) at 296, 303, and 310 K, respectively. The CD spectra and FT-IR spectra have proved that the protein secondary structure changed in the presence of Jatrorrhizine in aqueous solution. The effect of common ions on the binding constants was also investigated. In addition, the thermodynamic functions standard enthalpy (DeltaH(0)) and standard entropy (DeltaS(0)) for the reaction were calculated to be -10.891 kJ.mol(-1) and 56.267 J.mol(-1) K(-1), according to the van't Hoff equation. These data indicated that hydrophobic and electrostatic interactions played a major role in the binding of Jatrorrhizine to HSA. Furthermore, the displacement experiments indicated that Jatrorrhizine could bind to the site I of HSA, which was also in agreement with the result of the molecular modeling study.

Berberine↗

PubMed2004

Rapid and sensitive determination of anthraquinones in Chinese herb using 1-butyl-3-methylimidazolium-based ionic liquid with beta-cyclodextrin as modifier in capillary zone electrophoresis.

The present study reported the ionic liquid (IL) used as running electrolyte in capillary zone electrophoresis (CZE) with beta-cyclodextrin (beta-CD) as modifier for the separation of anthraquinones extract of Chinese herb Paedicalyx attopevensis Pierre ex Pitard. The optimum running electrolyte was 60 mM 1-butyl-3-methylimizolium tetrafluoroborate (1B-3MI-TFB) solution with 4.0 mM beta-CD. The pH was 10.00 and the applied voltage was 20 kV with detection at 254 nm. The present method was compared with others and the effect of Joule heating was discussed as well. More significantly, this method is the development of the ionic liquids application to the capillary electrophoresis.

Anthraquinones↗

PubMed2004

A novel double coating for microemulsion electrokinetic chromatography with laser-induced fluorescence detection: as tested with amino acid derivatives.

A novel double coating (DC) was developed for fast and reproducible microemulsion electrokinetic chromatography (MEEKC), as tested with separation and determination of amino acids using laser-induced fluorescence (LIF) detection after derivatization with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol. The simple coating is a combination of a removable covalent layer and a dynamic SDS coating. Hexamethyldisilazane was utilized for the covalent layer that can be regenerated on-line. Compared with previous no-coating method, the analysis time was shortened; and the reproducibility of migration times was improved.

4-Chloro-7-nitrobenzofurazan↗

PubMed2004

Sensitive determination of sulfate in drinks and vegetables digests by Rayleigh light scattering technique.

In this paper, a novel and sensitive method based on Rayleigh light scattering technique (RLS) was proposed for the determination of sulfate using a conventional spectrofluorometer. Sulfate was transformed to BaSO4 particles, which displayed intense light scattering in aqueous solutions. The effects of factors such as wavelength, acidity, stabilizers and interferents were studied in detail. The RLS intensity of the BaSO4 suspension was obtained in 0.1 mol L(-1) of [H+] and the addition of 2 mL of cationic polyacrylamide (CPAM) with 7.05 x 10(-3) mmol mL(-1) charged cations and 1.0 mL of BaCl2.2H2O (5.0%) at 510 nm. In the range of 8-400 microg mL(-1), RLS intensity was linear to the concentration of BaSO4, and the detection limit was 0.3 microg mL(-1). To determine the feasibility of the proposed method, some samples of water, drinks, and vegetables digests were analyzed, and the results were in agreement with the standard turbidimetric method. Good recovery results were also obtained in the range of 94-105%. Although this method was limited in stability, it was characterized with simplicity, sensitivity, reliability, and little interference.

Beverages↗

PubMed2004

Spectrofluorimetric study of the binding of daphnetin to bovine serum albumin.

Daphnetin (7,8-dihydroxycoumarin), one of the major bioactive components isolated from Daphne odora (as glucoside), is a chelator, an antioxidant and a protein kinase inhibitor. In this paper, we report for the first time studies on the binding of daphnetin to bovine serum albumin (BSA) under physiological conditions with BSA concentration of 1.5 x 10(-6) mol l(-1) and drug concentration in the range of 6.7 x 10(-6) to 2.0 x 10(-5) mol l(-1). Fluorescence quenching spectra in combination with Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy was used to investigate the drug-binding mode, the binding constant and the protein structure changes in the presence of daphnetin in aqueous solution. The curvature of Scatchard plot indicates that daphnetin binds to more than one class of sites on BSA. The thermodynamic parameters, enthalpy change (deltaH) and entropy change (deltaS) were calculated to be -24.21 kJ mol(-1) and 19.30 J mol(-1) K(-1) according to van't Hoff equation, which indicated that hydrophobic and electrostatic interaction played main role in the binding of daphnetin to BSA.

Animals↗

PubMed2004

Binding of the bioactive component daphnetin to human serum albumin demonstrated using tryptophan fluorescence quenching.

Daphnetin (7,8-dihydroxycoumarin), one of the major bioactive components isolated from Daphne koreane Nakai, has been used in traditional Chinese medicine for the treatment of coagulation disorders. It is also a chelator, an antioxidant and a protein kinase inhibitor. In this paper, a combination of intrinsic fluorescence, Fourier transform infrared (FT-IR) spectroscopy and circular dichroic (CD) spectroscopy has been used to characterize the binding between daphnetin and human serum albumin (HSA) under physiological conditions with drug concentrations of 6.7 x 10(-6) - 2.3 x 10(-5) mol x L(-1), and a HSA concentration of 1.5 x 10(-6) mol x L(-1). Changes in the CD spectra and FT-IR spectra were observed upon ligand binding, and the degree of tryptophan fluorescence quenching did change significantly in the complexes. These data have proved the change in protein secondary structure accompanying ligand binding. The change in tryptophan fluorescence intensity was used to determine the binding constants. The thermodynamic parameters, the enthalpy change (DeltaH) and the entropy change (DeltaS) were calculated to be -12.45 kJ x mol(-1)and 52.48 J x mol(-1) x K(-1) according to the van't Hoff equation, which indicated that hydrophobic and electrostatic interactions played the main role in the binding of daphnetin to HSA, in accordance with the results of calculations performed on a Silicon Graphics Ocatane2 workstation. In addition, the binding distance between daphnetin and HSA was obtained (4.02 nm) based on the Forster energy transfer theory.

Circular Dichroism↗

PubMed2004

Study on the quantitative relationship between the structures and electrophoretic mobilities of flavonoids in micellar electrokinetic capillary chromatography.

Quantitative structure-mobility relationship (QSMR) models were developed between the structures of flavonoids and their eletrophoretic mobilities in micellar electrokinetic capillary chromatography. Molecular descriptors calculated from structure alone are used to represent molecular structures, moreover, Nt was defined by ourselves. Multiple linear regression and radial basis function neural networks (RBFNNs) are utilized to construct the linear and nonlinear prediction model, respectively. The optimal QSMR model developed was based on a 3-10-1 RBFNNs architecture. The root mean square errors in mobilities predictions for the data set was 0.1083 mobility unit (10(-4) cm2 V(-1) s(-1)). The prediction results were in good agreement with the experimental values.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2004

Interaction of isofraxidin with human serum albumin.

This study was designed to examine the interaction of isofraxidin with human serum albumin (HSA) under physiological conditions with drug concentrations in the range of 3.3 x 10(-6) mol L(-1)-3.0x10(-5) mol L(-1) and HSA concentration at 1.5 x 10(-6) mol L(-1). Fluorescence quenching methods in combination with Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy were used to determine the drug-binding mode, the binding constant and the protein structure changes in the presence of isofraxidin in aqueous solution. Spectroscopic evidence showed that the interaction results in one type of isofraxidin-HSA complex with binding constants of 4.1266 x 10(5) L mol(-1), 3.8612 x 10(5) L mol(-1), 3.5063 x 10(5) L mol(-1), 3.1241 x 10(5) L mol(-1) at 296 K, 303 K, 310 K, 318 K, respectively. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS) were calculated to be -10.08 kJ mol(-1) and 73.57 J mol(-1) K(-1) according to van't Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to HSA. The experiment results are nearly in accordance with the calculation results obtained by Silicon Graphics Ocatane2 workstation.

Circular Dichroism↗

PubMed2004

Binding of isofraxidin to bovine serum albumin.

The binding of isofraxidin to bovine serum albumin (BSA) was studied under physiological conditions with BSA concentration of 1.5 x 10(-6) mol x L(-1) and drug concentration in the range of 1.67 x 10(-6) mol x L(-1) to 2.0 x 10(-5) mol x L(-1). Fluorescence quenching spectra in combination with uv absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and CD spectroscopy was used to determine the drug-binding mode, binding constant, and the protein structure changes in the presence of isofraxidin in aqueous solution. The linearity of Scatchard plot indicates that isofraxidin binds to a single class of binding sites on BSA and the values given for the binding constants agree very closely with those obtained by the modified Stern-Volmer equation. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS), were calculated to be -17.63 kJ x mol(-1) and 51.38 J x mol(-1) x K(-1) according to the van't Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to BSA.

Animals↗

PubMed2004

Separation and determination of gentiopicroside and swertiamarin in Tibetan medicines by micellar electrokinetic electrophoresis.

Micellar electrokinetic electrophoresis was employed to determine two active components, gentiopicroside (GE) and swertiamarin (SW) in one Tibetan preparation medicine named shiweilongdankeli, two Tibetan herbal medicines named Gentiana rhodantha and Gentiana kitag and three other Chinese Gentiana medicines named Gentiana scabra, Gentiana rigescens and Gentiana macrophylla. The dissociation constants of gentiopicroside and swertiamarin determined by MEKC were 7.71 and 6.25. The optimum buffer system was 70 mm borate-10 mm sodium dodecylsulfate (SDS) -6% (v/v) ispropanol (pH 9.0). The voltage was 15 kV and detection was at 254 nm. The lower limits of detection (defined as a signal-to-noise ratio of about 3) were approximately 3.86 mg L(-1) for GE and 5.88 mg L(-1) for SW. The relative standard deviation of the migration time and peak area of the GE and SW were 2.33, 2.47 and 1.27, 2.19%, respectively and the recoveries of the two compounds were 96-104% for GE and 92-102% for SW.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2004

Identification and determination of active anthraquinones in Chinese teas by micellar electrokinetic capillary chromatography.

The simultaneous determination of emodin, aloe-emodin and rhein, in Semen Cassiae, Qinghai Wild Dahuang tea, Ningxia Juemingzi tea, Lanzhou Juemingzi tea and Surong Juemingzi tea, has been investigated by micellar electrokinetic capillary chromatography for the fi rst time. With an electrolyte containing 15 mm borax, 30 mm SDS, 10% (v/v) ethanol, at pH 9.60 and 20 kV applied voltage, the three analytes were completely separated within 12 min. The effects of the concentration of borax, electrolyte pH, the concentrations of SDS and organic modifier and the applied voltage on electropheoretic behavior and separation were studied. The linear calibration range was 4-120 micro g/mL (r = 0.9921) for emodin, 10-200 micro g/mL (r = 0.9970) for aloe-emodin and 2-100 micro g/mL (r = 0.9971) for rhein, respectively. Under the optimum conditions, the relative standard deviation (RSD) values (n = 6) of the migration time and the peak area of each peak was 0.59-0.80% and 1.30-3.22%, respectively. The contents of the analytes in Rheum, Qinghai Wild Dahuang tea, Semen Cassiae and three other kinds of teas were easily determined with recoveries ranging from 95.3 to 104.4%.

Anthraquinones↗

PubMed2004

Analysis of the aconitine alkaloids in traditional Chinese medicines by nonaqueous capillary electrophoresis using a new recording mode.

The determination of three aconitine alkaloids (hypaconitine, aconitine, mesaconitine) in five traditional Chinese medicines including two Tibetan medicines, Chuanwu, Caowu, Fuzi, Aconitum Tanguticum Maxim and Aconitum Gymnandrum Maxim by non-aqueous capillary electrophoresis using a new recording mode is described. The dissociation constants of aconitine, mesaconitine and hypaconitine have also been determined by CZE and were 7.71, 6.60 and 6.25, respectively. The separation was achieved by optimizing the applied voltage, the pH and the concentration of the buffer. The electrophoretic medium was 20 mM borax-70% (v/v) methanol (pH 8.5) and an uncoated capillary (50 cm x 75 microm i.d.) was used. Detection was carried out with a UV monitor at 214 nm. The total time for separation and determination was under 13 min.

Aconitine↗

PubMed2004

Continuous capillary electrophoresis with flow injection and its application for determination of Ephedrine and Pseudo-ephedrine in Chinese medicinal preparations.

This article presents a new, simple and rapid continuous separation method by combination of flow injection with capillary electrophoresis designed for the analysis of basic traditional Chinese medicines. The device was produced using commercial capillary and components readily available in analytical laboratory. In double-T configuration, the designed horizontal separation channel was 25 microm i.d. x 146 mm length (an effective separation length of 93 mm) quartz capillary, with two vertical elicitation arms produced from 0.5 mm i.d. pump tubing. The capillary was embedded in a 40 x 20 x 3 mm organic glass base. Using the double-T configuration, continuous introduction of a series of samples was achieved. More than 3.00 resolution for ephedrine and pseudo-ephedrine were obtained using 100 mm borate buffer (pH 9.80) within 8 min in 25 microm separation channel with an electrical field strength of 137 V/cm (UV detection at 215 nm). The linear calibration range was 50-1500 microg/mL (ephedrine, r = 0.9982; pseudo-ephedrine, r = 0.9990) for both analytes. The limits of detection were 2.65 micro g/mL for ephedrine and 2.92 microg/mL for pseudo-ephedrine. In this device, the contents of ephedrine and pseudo-ephedrine in five Chinese medicinal preparations were determined with RSDs (n = 5) in range 1.16-4.51% and recoveries in range 90.4-114.6%.

Drugs, Chinese Herbal↗

PubMed2004

Simultaneous determination of some active ingredients in anti-viral preparations of traditional Chinese medicine by micellar electrokinetic chromatography.

A simple and rapid micellar electrokinetic chromatography method was developed for the simultaneous determination of quercetin, gentiopicrin, forsythin, chlorogenic acid and caffeic acid in anti-viral preparations of traditional Chinese medicine (apTCM). In this method, the effects of buffer pH, concentration of the borax and SDS, organic modifiers, applied voltage and temperature on the separation were tested and discussed. The results showed that the fi ve analytes could be well separated within 11 min under conditions of 40 mM borax (pH 9.65) containing 20 mM SDS, 20 kV, at 25 degrees C. In the tested concentration range, regression equations revealed good linear relationships (correlation coefficients 0.9920-0.9991) between the peak areas and corresponding concentrations. In addition, a multiple linear regression QSPR model was constructed to predict the migration times of the analytes and the results were satisfactory. The method was validated by analysis of the five compounds in three representative apTCM samples with recoveries ranging from 89.2 to 106.6%.

Antiviral Agents↗

PubMed2004

Microemulsion electrokinetic chromatography with laser-induced fluorescence detection for sensitive determination of ephedrine and pseudoephedrine.

A selective and sensitive microemulsion electrokinetic chromatography with laser-induced fluorescence detection method was developed for the quantification of ephedrine (E) and pseudoephedrine (PE) derivatized with 4-chloro-7-nitrobenzo-2-oxa-1, 3-diazol. By a series of optimization, a running buffer composed of 20 mM borate + microemulsion (23.3 mM Sodium dodecyl sulfate/180.85 mM 1-butanol/16.4 mM n-heptane) +8% acetonitrile was applied for the separation of the derivatives. A linear relationship for E and PE was obtained in the range of 0.058-11.58 microg.mL(-1) (correlation coefficient: 0.9993 for E, 0.9995 for PE), and the detection limits for E and PE were 5.3 and 3.9 ng.mL(-1). The method was applied to the analysis of the two alkaloids in Chinese traditional herbal preparations with recoveries in the range of 96.9-105.4%.

Alkaloids↗

PubMed2004

Continuous on-line derivatization and selective separation of D-aspartic acid by a capillary electrophoresis system with a continuous sample introduction interface.

A rapid and selective method is described for the separation of D-aspartic acid (D-Asp) using a continuous on-line derivatization system coupled to capillary electrophoresis (CE). D-Asp was derivatized using o-phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC). By on-line derivatization, amino acid enantiomers were automatically and reproducibly converted to the UV-absorbing diastereomer derivatives which were separated by capillary zone electrophoresis (CZE) in the presence of 10 mmol/L beta-cyclodextrin (beta-CD). Under the investigated separation conditions, D-Asp is resolved from L-aspartic acid (L-Asp) and other amino acids in a standard mixture of amino acids. The separation could be achieved within 4 min and the sample throughput rate can reach up to 16 h(-1). The repeatability (defined as relative standard deviation, RSD) was 3.21%, 3.58% with peak area evaluation and 3.72%, 4.03% with peak height evaluation for L-Asp and D-Asp.

Calibration↗

PubMed2004

Separation and determination of aconitine alkaloids in traditional Chinese herbs by nonaqueous capillary electrophoresis.

An easy, rapid, and simple nonaqueous capillary electrophoresis (NACE) method was developed for the identification and determination of three aconitine alkaloids, hypaconitine (HN), aconitine (AN), and mesaconitine (MN) within 6 min. The most suitable running buffer was composed of 60 mM ammonium acetate, 0.5% acetic acid, and 15% acetonitrile (ACN) in methanol with a fused-silica capillary column (50 cm x 75 microm ID). In the concentration range 12.5-1000 mg/L the calibration curves reveal linear relationships between the peak area for each analyte and its concentration (correlation coefficients: 0.9997 for HN, 0.9999 for AN, and 0.9995 for MN). The relative standard deviations of the migration time and peak area of the three alkaloids were 0.13, 0.57, 0.33 and 2.87, 1.06, 3.49%, respectively. The method was successfully applied to determine the three alkaloids in two commonly used traditional Chinese herbal medicines, the recoveries of the three constituents ranging between 94.7-101.9% for HN, 98.3-102.3% for AN, and 98.1-104.6% for MN.

Aconitine↗

PubMed2004

The combination of flow injection with electrophoresis using capillaries and chips.

The combined flow injection capillary electrophoresis (FI-CE) system that integrates the essential favorable merits of FI and CE, can significantly expand the application scope of CE by exploring the various on-line sample pretreatments and preconcentration of FI. The principle behind this technique, some innovative designs of the split-flow interface, as well as novel applications to a variety of analytical problems, are reviewed and discussed. Some salient features and unique advantages of this technique are outlined.

Calibration↗