Simultaneous enantio- and diastereo-selective high-performance liquid chromatography separation of paroxetine on an immobilized amylose-based chiral stationary phase under green reversed-phase conditions.

A simple and green high-performance liquid chromatography method for the separation of paroxetine from its enantiomeric and diastereomeric impurities has been developed. The simultaneous chromatographic resolution was carried out on the amylose-based Chiralpak IA-3 chiral stationary phase using the mixture ethanol-water-diethylamine 80:20:0.1 (v/v/v) as a mobile phase. The effects of substitution of ethanol with methanol or acetonitrile and changes in column temperature on selectivity have been carefully investigated. The optimized single-run HPLC protocol allows the baseline separation of the enantiomers of paroxetine without suffering from interference from five other chiral and achiral impurities reported in the monograph of the European Pharmacopoeia.

Magnetic solid-phase extraction coupled with UHPLC-MS/MS for four antidepressants and one metabolite in clinical plasma and urine samples.

Aim: Routine therapeutic drug monitoring is highly recommended since common antidepressant combinations increase the risk of drug-drug interactions or overlapping toxicity. Materials & methods: A magnetic solid-phase extraction by using C18-functionalized magnetic silica nanoparticles (C18-Fe3O4@SiO2 NPs) as sorbent was proposed for rapid extraction of venlafaxine, paroxetine, fluoxetine, norfluoxetine and sertraline from clinical plasma and urine samples followed by ultra-HPLC-MS/MS assay. Results: The synthesized C18-Fe3O4@SiO2 NPs showed high magnetization and efficient extraction for the analytes. After cleanup by magnetic solid-phase extraction, no matrix effects were found in plasma and urine matrices. The analytes showed LODs among 0.15-0.75 ng ml-1, appropriate linearity (R ≥ 0.9990) from 2.5 to 1000 ng ml-1, acceptable accuracies 89.1-110.9% with precisions ≤11.0%. The protocol was successfully applied for the analysis of patients' plasma and urine samples. Conclusion: It shows high potential in routine therapeutic drug monitoring of clinical biological samples.

Bioremediation of bezafibrate and paroxetine by microorganisms from estuarine sediment and activated sludge of an associated wastewater treatment plant.

The present work aimed to explore the potential of autochthonous microorganisms from an urban estuary and from activated sludge of an associated wastewater treatment plant (WWTP), for biodegradation of an antidepressant drug, paroxetine, and on a cholesterol-lowering agent, bezafibrate. These compounds were chosen as representatives of extensively used pharmaceuticals. Autochthonous microorganisms from the indicated sources were exposed to the target pharmaceuticals (1 mg/L) in co-metabolism with sodium acetate (500 mg/L) along a two-weeks period, for a total of 7 two-weeks periods (here referred as cycles). Exposures were carried out in batch mode, under different incubation conditions (agitation vs. static). Removal of pharmaceuticals was monitored at the end of each cycle, by analysing the culture medium. For paroxetine, fluoride ion release was also followed as an indicator of defluorination of the molecule. The structure of the bacterial communities was analysed by ARISA (Automated rRNA Intergenic Spacer Analysis), at the beginning of the experiment and at the end of the first and the last cycles to identify substantial changes associated with the time of exposure, the incubation conditions and the presence and type of pharmaceuticals. Incubation conditions affected not only the bacterial community structure, but also the biodegradation efficiency. At the beginning of the experiment, removal of target pharmaceuticals was found to be lower under agitation than under static conditions, but at the end of the experiment, results showed high removal of the pharmaceuticals from the culture medium (>97%) under both conditions, mainly by microbiological processes. For paroxetine, adsorption and abiotic processes also had an important influence on its removal, but defluorination only occurred in the presence of microorganisms. These results highlight that autochthonous microorganisms from estuarine sediments and WWTP sludge have high ability to remove the selected pharmaceuticals with relevant implications for the development of new bioremediation tools for environmental restoration.

Stereoselectiveseparation of racemic trans-paroxol, N-methylparoxetine and paroxetine containing two chiral carbon centres by countercurrent chromatography.

Racemic trans-paroxol, trans-N-methylparoxetine and trans-paroxetine containing two chiral centres were stereoselectively separated using countercurrent chromatography with hydroxypropyl-ß-cyclodextrin as the chiral selector. A two-phase solvent system composed of n-butyl acetate and 0.1 mol L-1 sodium carbonate-sodium bicarbonate buffer at pH 9.2 (1:1, v/v) was selected, and 0.10 mol L-1 hydroxypropyl-ß-cyclodextrin was added to the aqueous phase as the chiral selector. Racemic trans-N-methylparoxetine and racemic trans-paroxol (20 mg of each) were stereoselectively separated by countercurrent chromatography in an individual run, yielding 7.1-8.3 mg of enantiomers with a purity of 95-98%, where the recovery of each separated isomer reached approximately 70-83%. Racemic trans-paroxetine (20 mg) was stereoselectively separated by countercurrent chromatography using a recycling elution mode with a biphasic solvent system composed of n-hexane: n-butyl acetate: 0.1 mol L-1 sodium carbonate-sodium bicarbonate buffer at pH 9.2 (9:1:10, v/v/v), and 0.10 mol L-1 hydroxypropyl-ß-cyclodextrin was added to the aqueous phase as the chiral selector, yielding 5.0-5.6 mg of enantiomer with a high purity of over 98-99%.

Exploring the enantiorecognition mechanism of Cinchona alkaloid-based zwitterionic chiral stationary phases and the basic trans-paroxetine enantiomers.

The enantiomers of trans-paroxetine (the selectand) were separated on four chiral stationary phases incorporating either quinine [ZWIX(+), ZWIX(+A)] or quinidine [ZWIX(-), ZWIX(-A)] and (R,R)-aminocyclohexanesulfonic acid [in ZWIX(-), and ZWIX(+A)] or (S,S)-aminocyclohexanesulfonic acid [in ZWIX(+), and ZWIX(-A)] chiral selectors. The zwitterion nature of the phases is due to the presence of either (R,R)- or (S,S)-aminocyclohexanesulfonic acid in the selector structure bearing the quinuclidine moiety. ZWIX(+) and ZWIX(-) phases are available on the market with the commercial names CHIRALPAK ZWIX(+) and CHIRALPAK ZWIX(-), respectively. With the aim of rationalizing the enantiomer elution order with the above chiral stationary phases, a molecular dynamic protocol was applied and two energetic parameters were initially measured: selectand conformational energy and selectand interaction energy. In the search for other descriptors allowing a better fitting with the experimental evidences, in the present work we consider an energetic parameter, defined as the selector conformational energy, which resulted to be relevant in the explanation of the experimental elution order in most of the cases. Very importantly, the computational data produced by the present study strongly support the outstanding role of the conformational energy of the chiral selector as it interacts with the analytes.

Fast separation of selective serotonin reuptake inhibitors antidepressants in plasma sample by nonaqueous capillary electrophoresis.

A simple, fast, and sensitive liquid-liquid extraction method followed by nonaqueous capillary electrophoresis (LLE/NACE) was developed and validated for simultaneous determination of four antidepressants (fluoxetine, sertraline, citalopram and paroxetine) in human plasma. Several experimental separation conditions using aqueous and nonaqueous media separation were tested by varying the electrolyte pH value (for aqueous medium) and the ionic strength concentration considering the similar mobility of the compounds. High-resolution separation was achieved with a mixture of 1.25 mol L(-1) of phosphoric acid in acetonitrile. The quantification limits of the LLE/CE method varied between 15 and 30 ng mL(-1), with a relative standard deviation (RSD) lower than 10.3%. The method was successfully applied in therapeutic drug monitoring and should be employed in the evaluation of plasma levels in urgent toxicological analysis.

Kinetic and equilibrium study of the enantioseparation of paroxetine intermediate on amylose and tartaric acid-based chiral stationary phases.

trans-(-)-Paroxetine is a selective 5-hydroxytryptamine (5-HT) reuptake inhibitor currently used as an antidepressant. trans-(+/-)-3-Ethoxycarbonyl-4-(4'-fluorophenyl)-1-methylpiperidine-2,6-dione is an important intermediate of trans-(-)-paroxetine. It was separated on amylose and tartaric acid-based chiral stationary phases by HPLC. The equilibrium constants and overall mass transfer coefficients together with the axial dispersion coefficients were experimentally determined by moment analysis based on the lumped kinetic model of chromatography. In case of Kromasil CHI-TBB, the equilibrium constants measured were found to be 8.36 and 9.37 for trans-(+) and trans-(-) enantiomers, respectively. For Chiralpak AD-H, the equilibrium constants were 6.68 and 4.13 for trans-(+) and trans-(-) enantiomers, respectively. The axial dispersion coefficients of both enantiomers on Kromasil CHI-TBB column were about one order of magnitude greater than on Chiralpak AD-H. Fast kinetics of mass transfer in both chiral stationary phases was observed. Their overall mass transfer coefficients on Kromasil CHI-TBB and Chiralpak AD-H were 32.12, 33.18, 26.50, 46.85 s(-1) for trans-(+) and trans-(-) enantiomers, respectively. The parameters obtained were utilized to simulate the elution profiles, and the simulated and experimental results match well, which confirmed that the parameters obtained in this study were valid.

[Separation of paroxetine and its intermediate enantiomers by high performance liquid chromatography using carboxymethyl-beta-cyclodextrin as chiral mobile phase additive].

A high performance liquid chromatographic method to separate the respective enantiomers of paroxetine and its intermediate was developed using chiral mobile phase additive. Separation was performed on a Diamond C18 column (4.6 mm x 250 mm, 5 microm). The mobile phase was 0.1% phosphate acid-methanol (65 : 35, v/v) containing 0.38 g/L carboxymethyl-beta-cyclodextrin and the pH was adjusted to 7.2 by triethylamine. The detection wavelength was set at 210 nm and the temperature was 25 degrees C. With this method, paroxetine's trans/cis isomers and their enantiomers as well as intermediate HFP's trans/cis isomers and their enantiomers were separated simultaneously. The method is simple, rapid with high resolutions.

Simultaneous determination of human plasma levels of four selective serotonin reuptake inhibitors by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatography (HPLC) method with fluorimetric detection, which allows the simultaneous determination of plasma concentrations of four selective serotonin reuptake inhibitors (SSRIs) is presented. Fluvoxamine, paroxetine, sertraline, and fluoxetine were extracted from plasma with ethyl acetate and then derivatized with dansyl chloride. The analytes were separated using Hypersyl ODS C18 (5 microm) 250 x 4.6 mm column (ThermoQuest, Runcorn, UK). For continuous gradient separation, the mobile phase consists of two eluents, acetonitrile and potassium phosphate buffer (10 mmol/L, pH 7.2) at total flow rate of 1.5 mL/min. Detection was carried out at lambda exc = 366 nm and lambda em = 490 nm. The authors found recoveries of 90% to 95% for fluvoxamine, 94% to 100% for paroxetine, 88% to 95% for sertraline, 93% to 100% for fluoxetine, and 97% to 100% for internal standard (nortriptyline). Imprecision of the method ranged from 2.5% to 8.9%. The assay was linear from 10 to 1500 ng/mL for sertraline, and from 5 to 1500 ng/mL for the other drugs. The authors conclude that this method is suitable for monitoring antidepressant therapy. In addition, the authors report the effects of adding paroxetine to fluvoxamine on plasma levels in a group of patients in combined drug therapy.