A novel chiral GC/MS method for the analysis of fluoxetine and norfluoxetine enantiomers in biological fluids

Analysis of 15 anti-obesity drugs in urine using thermal-assisted paper spray mass spectrometry

Anti-obesity drugs, used to suppress appetite and reduce fat absorption, have been circulated and traded illegally worldwide. The traditional methods of liquid chromatography tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) for analyzing these drugs in in vivo samples require complex sample pretreatment and time-consuming procedures. To address this issue, a thermal-assisted paper spray mass spectrometry (PS-MS) method was developed in this study to analyze anti-obesity drugs in raw urine. By incorporating a heat source and optimizing the spray solvent and paper substrate, this technique demonstrates reduced matrix effect and higher sensitivity compared to traditional PS-MS methodology for direct analysis of anti-obesity drugs in urine samples. A temperature range of 100-200 °C can be set for screening anti-obesity drugs in urine samples, with the flexibility to adjust the temperature according to the specific drug being analyzed. The limits of detection (LODs) for these 15 anti-obesity drugs in urine ranged between 1 and 500 ng mL-1. Furthermore, the thermal-assisted PS-MS method exhibited good linearities (R2, 0.9903-0.9997) within the range from 10-100 to 1000 ng mL-1 for the direct quantitation of anti-obesity drugs in urine samples with an internal standard. Therefore, the thermal-assisted PS-MS technique may provide a novel approach for the direct analysis of drugs in complex samples.

Demystifying racemic natural products in the homochiral world

Natural products possess structural complexity, diversity and chirality with attractive functions and biological activities that have significantly impacted drug discovery initiatives. Chiral natural products are abundant in nature but rarely occur as racemates. The occurrence of natural products as racemates is very intriguing from a biosynthetic point of view; as enzymes are chiral molecules, enzymatic reactions generating natural products should be stereospecific and lead to single-enantiomer products. Despite several reports in the literature describing racemic mixtures of stereoisomers isolated from natural sources, there has not been a comprehensive review of these intriguing racemic natural products. The discovery of many more natural racemates and their potential enzymatic sources in recent years allows us to describe the distribution and chemical diversity of this 'class of natural products' to enrich discussions on biosynthesis. In this Review, we describe the chemical classes, occurrence and distribution of pairs of enantiomers in nature and provide insights about recent advances in analytical methods used for their characterization. Special emphasis is on the biosynthesis, including plausible enzymatic and non-enzymatic formation of natural racemates, and their pharmacological significance.

Development and validation of an automated solid-phase extraction-LC-MS/MS method for the bioanalysis of fluoxetine in human plasma

A wide-range, specific, and precise liquid chromatography tandem mass spectrometric (LC-MS/MS)technique for quantifying fluoxetine (FLX) in human plasma was developed using the RapidTrace^® automated solid-phase extraction (SPE) method; the analyte and internal standard (IS) were extricated on Oasis MCX SPE cartridges. Acetonitrile and 5 mM ammonium formate buffer (90:10 v/v) were used as mobile phase to achieve chromatographic separation on the reverse phase (C₁₈ column). The analyte and IS were ionized using +ve electrospray ionization approach which was further traced by multiple-reaction monitoring on a tandem mass spectrometer. To quantify the FLX and FLX-d5, the parent-to-daughter ion transition of m/z of 310.0/44.1 and 315.0/44.0 was used, respectively. The method demonstrated a linear active limit of 0.20-30 ng/ml with recoveries ranging from 63.04% to 79.39% for quality control samples and 61.25% for IS samples. The concentrations over the calibration range demonstrated acceptable precision and accuracy. Due to the high inconsistency of the FLX concentration data, the minimum threshold of the assay was kept at 0.20 ng/ml. The flow rate was maintained at 500 μL/min, and the time for sample analysis for each injection was 3.5 min. The method was found to be specific, sensitive, and faster with minimum utilization of organic solvents and was utilized further for metabolic and pharmacokinetic studies.

Simultaneous quantification of vortioxetine, fluoxetine and their metabolites in rat plasma by UPLC-MS/MS

In this study, a specific and quick ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was fully developed and validated for simultaneous measurement of the rat plasma levels of vortioxetine (VOR), Lu AA34443 (the major metabolite of VOR), fluoxetine and its metabolite norfluoxetine with diazepam as the internal standard (IS). After a simple protein precipitation with acetonitrile for sample preparation, the separation of the analytes were performed on an Acquity UPLC BEH C18 (2.1 × 50 mm, 1.7 μm) column, with acetonitrile and 0.1% formic acid in water as mobile phase by gradient elution. The detection was achieved on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring mode via an electrospray ionization source. Good linearity was observed in the calibration curve for each analyte. The data of precision, accuracy, matrix effect, recovery and stability all conformed to the bioanalytical method validation of acceptance criteria of US Food and Drug Administration recommendations. The newly developed UPLC-MS/MS method allowed simultaneous quantification of VOR, fluoxetine and their metabolites for the first time and was successfully applied to a pharmacokinetic study in rats.

Simultaneous determination of fluoxetine, venlafaxine, vortioxetine and their active metabolites in human plasma by LC-MS/MS using one-step sample preparation procedure

The aim of antidepressant therapy is to induce remission and prevent relapses of major depressive disorder with minimum adverse effects during the treatment. Due to high variability in metabolism, therapeutic drug monitoring is recommended as a useful tool for individualisation of the therapy. For this purpose, we have developed simple and sensitive ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for quantification of fluoxetine (FLX), venlafaxine (VEN), vortioxetine (VTX) and their active metabolites norfluoxetine (NFLX) and O-desmethylvenlafaxine (ODV). After one-step extraction procedure using OSTRO plate, analytes were separated by gradient elution on Acquity UPLC BEH C18 (50 × 2.1 mm, 1.7 μm) column with runtime 4.2 min. The detection was done on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode with transitions at m/z 310.23 → 148.20 for FLX, m/z 296.23 → 134.20 for NFLX, m/z 278.31 → 121.13 for VEN, m/z 264.31 → 107.14 for ODV and m/z 299.19 → 150.05 for VTX using a positive electrospray ionisation interface. The method was successfully validated according to the European Medicine Agency guideline for the selectivity, linearity and lower limit of detection, precision and accuracy, matrix effect, extraction recovery, carryover, dilution integrity and stability over a concentration range of 1-300 ng/mL for FLX, NFLX, VEN, ODV and 0.2-100 ng/mL VTX. Extraction recovery for each analyte was > 80 %, and no significant matrix effects were observed. The developed method was employed for quantification of antidepressants in clinical samples from patients treated with either FLX, VEN, or VTX.

Pharmacokinetics and Tissue Distribution Kinetics of Puerarin in Rats Using Indirect Competitive ELISA

Puerarin (PUE) is a compound isolated from the roots of Pueraria lobata. We studied the pharmacokinetics and tissue distribution kinetics of PUE in Sprague-Dawley rats following intraperitoneal administration of three concentrations. Indirect competitive ELISA based on an anti-PUE monoclonal antibody was used to determine the concentration of PUE in the blood, heart, liver, spleen, lung, kidney, hippocampus, cerebral cortex, and striatum. The plasma and tissue distribution kinetic characteristics following a single injection of PUE (20, 40 and 80 mg/kg) were calculated using a non-compartment model. In the high-dose (80 mg/kg) and medium-dose (40 mg/kg) groups, the kinetic profile of PUE in blood and kidney samples showed two absorption peaks, while that of the other tissues showed only one peak. In the low-dose (20 mg/kg) group, there was only one peak, irrespective of the sample type. Pharmacokinetic parameters, such as the area under the curve, C_max, and T_max varied according to the administered dose. AUC and C_max values increased dose-dependently. PUE was widely distributed in areas of the brain such as the hippocampus, cerebral cortex, and striatum, providing a foundation for guiding the use of PUE in the treatment of cerebral ischaemic stroke and neurodegenerative diseases.

Determination of enantiomeric composition of fluoxetine by synchronous fluorescence spectrometry coupled with multivariate calibration in biological samples

This paper presents rapid and low cost analytical method for the determination of the fluoxetine enantiomeric composition in biological samples (urine). The combination of synchronous fluorescence spectrometry and inverse multivariate calibration methods was used. The chiral recognition of the fluoxetine was based on the creating of the diastereomeric complexes with β-cyclodextrin. A net analytical signal of diastereomeric complexes was obtained by the addition of aliquot part of urine into calibration and validation sets. This step ensures the elimination of the urine matrix effect. The synchronous fluorescence spectra at the constant wavelength differences (Δλ) of 30 and 50 nm, based on RMS %RE values, were chosen for chemometric analysis. Principal component regression (PCR) and partial least square method (PLS) were compared to determine the enantiomeric composition. The most suitable results were provided by the PLS model constructed from the synchronous data at Δλ = 50 nm. The calculated figure of merit was used for validation of proposed method.

Simultaneous enantioselective quantification of fluoxetine and norfluoxetine in human milk by direct sample injection using 2-dimensional liquid chromatography-tandem mass spectrometry

A two-dimensional liquid chromatography system coupled to triple quadrupole tandem mass spectrometer (2D LC-MS/MS) was employed for the simultaneously quantification of fluoxetine (FLX) and norfluoxetine (NFLX) enantiomers in human milk by direct injection of samples. A restricted access media of bovine serum albumin octadecyl column (RAM-BSAC18) was used in the first dimension for the milk proteins depletion, while an antibiotic-based chiral column was used in the second dimension. The results herein described show good selectivity, extraction efficiency, accuracy, and precision with limits of quantification in the order of 7.5ngmL(-1)for the FLX enantiomers and 10.0ngmL(-1) for NFLX enantiomers. Furthermore, it represents a practical tool in terms of sustainability for the sample preparation of such a difficult matrix.