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Reversed-phase High Performance Liquid Chromatography (reversed-phase + high_performance_liquid_chromatography)
Selected AbstractsLornoxicam pharmacokinetics in the vitreous humor of albino rabbitsACTA OPHTHALMOLOGICA, Issue 2009C TSIKA Purpose To assess the elimination half-life of intravitreal lornoxicam, a non-steroidal anti-inflammatory drug (NSAID). Methods Both eyes of 15 rabbits were intravitreally injected with 250 ,g of commercially available lornoxicam (for intravenous/intramuscular use, Xefo® 8 IV/IM Injection, Nycomed Hellas S.A.). Six eyes were enucleated at time points 0, 1, 2, 6 and 24 hours after the injection was performed. The eyes were immediately frozen at -80°C. The vitreous was eviscerated from the eye and the drug was liquid-liquid extracted from a 0.4 ml sample. Lornoxicam was isolated by a reversed-phase High Performance Liquid Chromatography (HPLC) method at retention time 10.7 min and detected at 372 nm. The data were statistically analyzed in order to evaluate the pharmacokinetic parameters of the drug. Results The recovery of lornoxicam after liquid-liquid extraction was calculated at 69.6% and the limit of determination was 0.1 ,g/ml. Statistical analysis revealed that lornoxicam concentrations followed first-order kinetics with an elimination rate constant of 0.235h-1 and a half-life of 3.0 h. Conclusion The determination of the pharmacokinetic characteristics of intravitreal lornoxicam allows the possibility for further investigation of the drug's intraocular behaviour and therapeutic potential. [source] Preparation and characterization of PEGylated terlipressinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Xiufang Wang Abstract Terlipressin was chemically modified by reaction with succinimidyl propionate- monomethoxy polyethylene glycol (mPEG-SPA). To determine the PEGylated degree, the position and the optimized condition for PEGylated terlipressin, the reactions were monitored in different pH value buffers at different molar ratios by reversed-phase high performance liquid chromatography (RP-HPLC). Tryptic digestion and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used. The results showed that the amount of mono-PEG-terlipressin was higher at lower pH value and lower content of PEG. Meanwhile, the amount of di-PEG-terlipressin was higher at higher pH value and higher content of PEG under the conditions investigated. The position of PEGylated terlipressin was confirmed by tryptic digestion. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Analysis of phenolic acids in honeys of different floral origin by solid-pase extraction and high-performance liquid chromatographyPHYTOCHEMICAL ANALYSIS, Issue 1 2007Burya Dimitrova Abstract The determination of 18 aromatic and arylaliphatic carboxylic acids in honey from different floral origin using solid-phase extraction (SPE) and reversed-phase high performance liquid chromatography (RP-HPLC) is reported. The behaviour of the solutes on SPE cartridges was predicted from preliminary calculations involving the pKa constants of the carboxylic groups, the n -octanol:water partition coefficients and the distribution coefficients at different pH values of the conditioning and washing solvents. The proposed SPE isolation and pre-concentration of the acids was achieved on reversed-phase Bond Elut C18 cartridges using an acetonitrile:tetrahydrofuran (1:1, v/v) elution system. RP-HPLC separations were performed on a Spherisorb ODS-2 column using linear gradient elution with a mobile phase composed of 20 mm phosphate buffer (pH 2.92) and methanol, and with UV detection. The reported SPE and RP-HPLC methods were applied to the analysis of 49 authentic honey samples from various floral sources and the results indicate that they may serve with respect to the quantitative control of a number of phenolic acids in plant-derived foods and medicinal plants. Copyright © 2006 John Wiley & Sons, Ltd. [source] Analysis of oxidation process of cholecystokinin octapeptide with reactive oxygen species by high-performance liquid chromatography and subsequent electrospray ionization mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Hideaki Ichiba Abstract The C -terminal octapeptide of cholecystokinin (CCK8) includes some easily oxidizable amino acids. The oxidation of CCK8 by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and hydroxyl radicals (OH,) was investigated using reversed-phase high performance liquid chromatography (RP-HPLC) and subsequent electrospray ionization mass spectrometry. The mechanism of oxidation of CCK8 in the H2O2 system differed from that of CCK8 in the Fenton system, in which OH, are produced. In the H2O2 system, 28Met and 31Met were oxidized to methionine sulfoxide, and no further oxidation or degradation/hydrolysis occurred. On the other hand, in the Fenton system, 28Met and 31Met residues were oxidized to methionine sulfone via the formation of methionine sulfoxide. In addition, the oxidized product was observed at the Trp residue but not at the Tyr residue, and small peptide fragments from CCK8 were observed in the Fenton system. From these results, it was concluded that 28Met and 31Met residues of CCK8 are susceptible to oxidation by ROS. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effect of N- acetylcysteine on amphetamine-mediated dopamine release in rat brain striatal slices by ion-pair reversed-phase high performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Erzsébet Gere-Pászti Abstract The amphetamine (AMPH)-induced alteration in rat brain dopamine levels modified by N- acetylcysteine (NAC) administration has been examined using isocratic ion-pair reversed-phase high-performance liquid chromatography with electrochemical detection. The aim of the development of a novel validated evaluation scheme implying a double AMPH challenge was to enhance the efficiency of AMPH-triggered dopamine release measurements in rat brain striatal slices by improving the reproducibility of the results. The proposed experimental protocol was tested in vivo and proved to be capable of fast and reliable drug screening for tracing the effect of NAC as a model compound in AMPH-mediated dopaminergic response. The subcellular localization of the dopamine mobilizing effect of NAC has been established indirectly by the use of an irreversible dopamine vesicular depletor, reserpine. The antioxidant NAC at 10 mm plays an important role in the complete suppression of acute AMPH-elicited dopamine release. The possible role of this quenching effect is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of lipophilicity of , -(4-phenylpiperazine) derivatives of N -benzylamides using chromatographic and computational methodsBIOMEDICAL CHROMATOGRAPHY, Issue 4 2008Marek Bajda Abstract This paper describes the evaluation of lipophilicity of ,- (4-phenylpiperazine) derivatives of N -benzylamides. We employed reversed-phase thin-layer chromatography (RP-TLC) and reversed-phase high performance liquid chromatography (RP-HPLC) as experimental methods, using mixtures of acetonitrile and water as the mobile phases with addition of 0.1%TFA in the HPLC experiments. Retention parameters (RM) and capacity factors (log k) determined by applying these methods were linearly dependent on the acetonitrile concentration and enabled us to estimate the relative lipophilicity factors: RM0 and log k0. These factors were compared with the calculated partition coefficients C log P obtained using several software packages. The results indicate that both experimental methods (RP-TLC and RP-HPLC) yielded similar results, and these methods enable determining the lipophilicity of ,- (4-phenylpiperazine) derivatives of N -benzylamides. Significant correlations were found between log P values calculated by Pallas, ALOGPS and C log P Chem3D programs and the experimental data. Copyright © 2007 John Wiley & Sons, Ltd. [source] Transplacental transfer of citalopram, fluoxetine and their primary demethylated metabolites in isolated perfused human placentaBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 9 2002Tuija Heikkinen Objective To investigate the transplacental transfer and the effects of protein binding on the transfer of citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine in the isolated perfused human placenta model. Design Prospective observational study. Methods Fifteen term human placentas were obtained immediately after delivery with maternal consent and a 2-hour non-recirculating perfusion cycle of a single placental cotyledon was set up. Citalopram (1230 nmol/L) and desmethylcitalopram (600 nmol/L) or fluoxetine (1455 nmol/L) and desmethylfluoxetine (1525 nmol/L) were added to the maternal reservoir and their appearance to the fetal circulation was followed by repeated measurements. To investigate the effect of protein binding on the transfer of citalopram and fluoxetine, nine additional perfusions were performed without albumin in the perfusion medium. Citalopram and desmethylcitalopram concentrations were measured by reversed-phase high performance liquid chromatography. Fluoxetine and desmethylfluoxetine concentrations was measured by gas chromatography and antipyrine (used as a reference compound) concentrations spectrophotometrically. Results The mean (SD) steady-state transplacental transfer (TPTSS%) for citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine was 9.1%, 5.6% (P= 0.017 compared with citalopram), 8.7% and 9.1%, respectively, calculated as the ratio between the steady-state concentrations in fetal venous and maternal arterial sides. The TPTSS%s of citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine were 86%, 50%, 88% and 91% of that of freely diffusable antipyrine. The absence of albumin significantly reduced the transfer of citalopram and fluoxetine (TPTSS% 1.1% and 4.8%, respectively) but not the transfer of antipyrine. Conclusion Citalopram, fluoxetine and desmethylfluoxetine all cross the human placenta, and may, therefore, affect the perinatal outcome of infants exposed to these drugs during pregnancy. The transfer of desmethylcitalopram was significantly lower, which in the clinical setting may suggest lower fetal exposure of serotonin re-uptake inhibition by citalopram compared with fluoxetine. The presence of albumin was necessary for the transplacental transfer of both citalopram and fluoxetine. [source] | |||||||||||||