Xin Di

Microwave-assisted extraction in combination with capillary electrophoresis for rapid determination of isoquinoline alkaloids in Chelidonium majus L.

A simple and rapid method based on microwave-assisted extraction (MAE) followed by capillary electrophoresis (CE) was developed for the quantification of eight isoquinoline alkaloids in Chelidonium majus L. (Ch. majus). The key parameters affecting CE separation and MAE extraction were investigated and optimized. Complete separation of eight alkaloids was achieved within only 9 min using a 500 mM Tris-H(3)PO(4) buffer (pH 2.5) containing 50% (v/v) methanol and 2mM HP-β-cyclodextrin. The optimal MAE extraction was performed at 60 °C for 5 min with methanol-water-HCl (90:10:0.5, v/v/v) as the extracting solvent, which gave much higher extraction efficiency in significantly shorter time than conventional heat reflux extraction (HRE) and ultrasonic extraction (USE) methods. Good linearities were obtained for all the alkaloids investigated with correlation coefficients above 0.9994. The repeatability and intermediate precision were less than 4.11% and the recoveries ranged from 98.0% to 103.9%. The developed method was successfully applied to 14 Ch. majus samples obtained from different regions of China. Compared with previously reported methods, the present method offers a dramatic savings in overall analysis time and considerable reduction in solvent consumption.

A sensitive and selective liquid chromatography−tandem mass spectrometry method for simultaneous determination of five isoquinoline alkaloids from Chelidonium majus L. in rat plasma and its application to a pharmacokinetic study

Chelidonium majus L. is one of the most important medicinal plants of the family Papaveraceae. Its pharmacological effects have been primarily attributed to the presence of a number of alkaloids. In the present study, a sensitive and selective liquid chromatography-tandem mass spectrometry method for simultaneous determination of five isoquinoline alkaloids from Chelidonium majus L. was developed and validated. The analytes (protopine, chelidonine, coptisine, sanguinarine and chelerythrine), together with the internal standard (palmatine), were extracted from acidified rat plasma with ethyl acetate-dichloromethane (4:1, v/v). Chromatographic separation was carried out on a Diamonsil C(18) column with an isocratic mobile phase consisting of acetonitrile and water (adjusted to pH 2.3 with formic acid) (30:70, v/v) at a flow rate of 0.4u2009ml/min. Mass spectrometric detection was performed by selected reaction monitoring mode via electrospray ionization source operating in positive ionization mode. The assay exhibited good linearity (ru2009≥u20090.9933) for all the analytes. The lower limits of quantification were 0.197-1.27u2009ng/ml using only 50 µl of plasma sample. The intra- and inter-day precisions were less than 11.9%, and the accuracy was between -6.3% and 9.3%. The method was successfully applied to the pharmacokinetic study of the five alkaloids in rats after intragastric administration of Chelidonium majus L. extract.

Capillary electrophoresis with noncovalently bilayer-coated capillaries for stability study of allergenic proteins in simulated gastrointestinal fluids

A novel noncovalently bilayer-coated capillary using cationic polymer polybrene (PB) and anionic polymer (sodium 4-styrenesulfonate) (PSS) as coatings was prepared. This PB-PSS coating showed good migration-time reproducibility for proteins and high stability in the range of pH 2-10 and in the presence of 1M NaOH, acetonitrile and methanol. Capillary electrophoresis with PB-PSS coated capillaries was successfully applied to quantitatively investigate the stability of bovine serum albumin, ovomucoid, β-lactoglobulin and lysozyme in simulated gastrointestinal fluids. β-lactoglobulin A and β-lactoglobulin B were both stable in simulated gastric fluid with degradation percentages of 34.3% and 17.2% after 60min of incubation, respectively. Bovine serum albumin, ovomucoid and lysozyme were stable in simulated intestinal fluid with degradation percentages of 17.7%, 23.4% and 22.8% after 60min of incubation, respectively. The superiority of the proposed method over sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and capillary electrophoresis with untreated fused silica capillaries was demonstrated and emphasized.

Development of a liquid chromatography-tandem mass spectrometry method for measuring plasma and uterine tissue levels of indomethacin in rabbits treated with indomethacin-medicated Cu-IUDs.

BACKGROUNDnSome side effects of copper intrauterine devices (Cu-IUDs) including increased uterine bleeding, pelvic infections and pain have been reported. The presence of indomethacin in such devices was found to be effective in relieving the symptoms. The aim of this study was to develop and validate a rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for measuring plasma and uterine tissue levels of indomethacin in rabbits after insertion of indomethacin-medicated Cu-IUDs.nnnSTUDY DESIGNnIndomethacin was extracted from rabbit plasma and uterine tissue by a simple protein precipitation using acetonitrile. Chromatographic separation was carried out on a Diamonsil C(18) column (150×4.6 mm ID, 5 μm) with an isocratic mobile phase consisting of methanol, acetonitrile, water and formic acid (45:45:10:0.5, v/v/v/v). Mass spectrometric detection was achieved by a triple-quadrupole mass spectrometer equipped with an atmospheric pressure chemical ionization interface operating in positive ionization mode. Quantitation was performed using selective reaction monitoring mode. The LC-MS/MS method was validated with respect to selectivity, linearity, precision, accuracy, extraction recovery and stability, and then applied to the in vivo studies of indomethacin in rabbits treated with indomethacin-medicated Cu-IUDs.nnnRESULTSnThe linear calibration curves of indomethacin in plasma and uterine tissue were obtained over the concentration range of 2.0-400 ng/mL and 4.0-800 ng/mL, respectively. The intra- and interday precision was less than 9.5%, and the relative error was within ±5.3%. After insertion of indomethacin-medicated Cu-IUDs in rabbits, indomethacin was rapidly absorbed, and peak plasma levels were reached in approximately 1 h. A multiphasic elimination pattern was observed, which was a rapid decline in plasma concentration during the first 100 h followed by a very slow clearance phase. The uterine indomethacin levels were significantly higher than simultaneous plasma levels.nnnCONCLUSIONSnThe developed method proved to be rapid and sensitive, and was successfully applied to investigate the absorption and uterine distribution of indomethacin in rabbits after insertion of indomethacin-medicated Cu-IUDs.

Development and validation of a rapid high-performance liquid chromatography-tandem mass spectrometry method for the determination of WJ-38, a novel aldose reductase inhibitor, in rat plasma and its application to a pharmacokinetic study

WJ-38 is an aldose reductase inhibitor that is being developed for the treatment of diabetic complications. The present paper describes a sensitive and specific liquid chromatography-tandem mass spectrometry method for the determination of WJ-38 in rat plasma. Partial denaturation of plasma proteins with methanol followed by liquid-liquid extraction using ethyl acetate was used to extract strongly protein-bound WJ-38 from rat plasma. Chromatographic separation was performed on an Inertsil ODS-3 column with an isocratic mobile phase consisting of acetonitrile, water and formic acid (75:25:0.125, v/v/v). Mass spectrometric detection was achieved by a triple-quadrupole mass spectrometer equipped with an ESI interface operating in positive ionization mode. Quantitation was performed using selected reaction monitoring of precursor-product ion transitions at m/z 392→246 for WJ-38 and m/z 446→321 for glipizide (internal standard). A linear calibration curve was obtained over the concentration range of 10.0-10,000 ng/mL for WJ-38 in rat plasma. The intra- and inter-day precisions were less than 13.6% and the accuracy was within ± 5.3%. The extraction recovery of WJ-38 from rat plasma was over 66.0%. The validated method has been successfully applied to a pharmacokinetic study in rats after intragastrical administration of WJ-38.

Reduced graphene oxide-supported gold dendrite for electrochemical sensing of acetaminophen

A new nanocomposite was developed based on reduced graphene oxide (RGO) supported gold dendrite and applied for amperometric detection of acetaminophen. The RGO-gold dendrite composite was prepared by self-assembly of poly (diallyldimethylammonium chloride) (PDDA) functionalized gold dendrite and poly (sodium 4-styrenesulfonate) (PSS) functionalized RGO. The composite electrode material was characterized by Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Ultraviolet-vis spectroscopy (UV), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The RGO-gold dendrite composite exhibited enhanced conductivity, catalytic activity and stability for acetaminophen oxidation and determination. The RGO-gold dendrite based electrochemical sensor is competent for detecting acetaminophen with a linear range from 0.07u202fµM to 3000u202fµM with a detection limit of 0.005u202fµM (S/Nu202f=u202f3). Moreover, the sensor was applied for the detection of acetaminophen in tablets and urine samples, which holds great promise in pharmaceutical analysis.

An LC–MS/MS method for the simultaneous determination of goserelin and testosterone in rat plasma for pharmacokinetic and pharmacodynamic studies

A liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed, using testosterone-d3 as a surrogate analyte, for the simultaneous quantification of goserelin and testosterone in rat plasma. According to this method, the pharmacokinetic and pharmacodynamic data were obtained from a single plasma sample aliquot. The method involved the addition of alarelin as an internal standard (IS) for goserelin and testosterone-(13)C3 for testosterone or testosterone-d3. The conditions for the separation of these two compounds were achieved on a ZORBAX Eclipse Plus C18 column (Agilent, 2.1 × 50 mm, 1.8 μm, Stockport, UK) in a single chromatographic run at a flow rate of 400 μL/min. In order to minimize interferences of complex matrix, the extraction of plasma consisted of a protein precipitation step using methanol, followed by purification using an Oasis(®) HLB solid-phase extraction column. The method was validated in the concentration range of 0.01-30.0 ng/mL for goserelin and 0.05-30.0 ng/mL for testosterone-d3, respectively. The within- and between-run precisions were 1.7-9.2% and 2.1-6.9%, respectively. The within- and between-run accuracies were -1.8 to 5.3% and -4.9 to 4.0%, respectively. This accurate and highly specific assay provides a useful method to evaluate the pharmacokinetics and pharmacodynamics of goserelin in rats.