A GC-SIM-MS Method for the Determination of Butylidenephthalide in Rat Plasma and Tissue: Application to the Pharmacokinetic and Tissue Distribution Study

Abstract

Butylidenephthalide is one of the major active components isolated from Rhizoma Chuanxiong. This paper describes a simple, rapid, specific and sensitive method for the quantification of butylidenephthalide in rat plasma and tissue distribution using a liquid-liquid extraction procedure followed by capillary gas chromatography-selected ion monitoring mode-mass spectrometry (GC-SIM-MS) analysis. The calibration curves were linear over the concentration ranging from 0.02–10.0 µg/mL (r > 0.99) for plasma samples and 0.18–7.25 µg/g (r > 0.99) for the tissue samples. The limit of quantification (LOQ) was 1.0 ng/mL or 1.0 ng/g (ten times signal/noise ratio). Within- and between-day precisions expressed as the relative standard deviation (RSD) for the method were 2.39–2.98% and 2.97–4.26%, respectively. The methods of recovery for all samples were greater than 80% at the low, medium, and high concentrations. The method has been successfully applied to a pharmacokinetics study in rats after an oral administration of Butylidenephthalide with a dose of 20.0 mg/kg. The main pharmacokinetic parameters obtained were T _max  = (0.22 ± 0.06) h, C _max = (3 ± 1) µg/mL, AUC = (32 ± 6) h?µg/mL, and K _a  = (8.5 ± 0.8)/h. The results showed that the butylidenephthalide was easily absorbed. The concentrations of butylidenephthalide in rat kidney, lung, heart, and cerebellum were higher than those in other organs. To determine free fraction in serum, samples were filtered using ultrafiltration membranes with a molecular weight cut-off of 10,000 Da and extracted using liquid-liquid extraction. The extracts were evaporated and analyzed by GC-MS. The protein binding in rat plasma, human plasma, and human serum albumin were 83 ± 4%, 94 ± 3%, and 89 ± 3%, respectively.     

Reversed–Phase Liquid Chromatographic Determination of Zaleplon in Human Plasma and its Pharmacokinetic Application

Abstract

A simple, rapid, specific, and reliable high performance liquid chromatographic assay of zaleplon in human plasma has been developed. Reversed‐phase chromatography was conducted using a mobile phase of methanol∶ammonium acetate buffer (50∶50) v/v, pH 3.2 adjusted with orthophosphoric acid, UV detection at 232 nm. After extraction from plasma by precipitation the drug was chromatographed using a C₁₈ reversed‐phase analytical column. The average recoveries of zaleplon from spiked plasma in the concentration range from 0.005–0.2 µg/ml were 93.29%, and their respective CV% was 2.557%. Regression analysis for the calibration plot for plasma standards obtained on three different days for the drug concentrations between 0.005–0.2 µg/ml indicated excellent linearity (r>0.999) and the coefficient of variation of the slopes of the three lines was less than 2%. The limit of detection was 5 ng/ml. Analysis of variance of the data showed no detectable difference in the slopes of the three standard plots (F=3.1, P>0.01). The high correlation coefficients and the similarities in the slopes are good indications of the excellent reproducibility and linearity of the proposed method. The proposed method was applied to study the bioequivalence of a commercial product of zaleplon, using as reference standard the innovator drug product. The study was conducted by using one capsule (1×10 mg) of each of the commercial product and the reference standard in a two‐way open randomized crossover design involving 24 volunteers. The criteria used to assess bioequivalence of the products were AUC (0?∞), C_max, t_max, t_1/2, and K. The obtained values for these parameters were 0.246±0.03 µg h/ml, 0.150±0.013 µg/ml, 1 h, 1.26±0.36 h, and 0.5928±0.1732 h^?1 for product A whereas, for product B they were 0.256±0.044 µgh/ml, 0.142±0.014 µg/ml, 1 h, 1.18±0.33 h, and 0.63±0.1747 h^?1, respectively.     

Rapid and Highly Sensitive HPLC and TLC Methods for Quantitation of Amlodipine Besilate and Valsartan in Bulk Powder and in Pharmaceutical Dosage Forms and in Human Plasma

Two simple, sensitive, and specific high-performance liquid chromatography and thin-layer chromatography methods were developed for the simultaneous estimation of Amlodipine besilate (AM) and Valsartan (VL). Separation by HPLC was achieved using a xTerra C18 column and methanol /acetonitrile /water/ 0.05% triethylamine in a ratio 40:20:30:10 by volume as mobile phase, pH was adjusted to 3 ± 0.1 with o-phosphoric acid. The flow rate was 1.2 mL min^?1. The linearity range was 0.2 to 2 µg mL^?1 for amlodipine besilate and 0.4 to 4 µg mL^?1 for Valsartan with a mean percentage recovery of 99.59 ± 0.523% and 100.61 ± 0.400% for amlodipine besilate and valsartan, respectively. The TLC method used silica gel 60 F₂₅₄ plates; the optimized mobile phase was ethyl acetate/ methanol / ammonium hydroxide (55:45:5 by volume). Quantitatively, the spots were scanned densitometrically at 237 nm. The range was 0.5–4.0 µg spot^?1 for amlodipine besilate and 2.0–12.0 µg spot^?1 for valsartan. The mean percentages recovery was 99.80 ± 0.451% and 100.61 ± 0.363% for amlodipine besilate and valsartan, respectively. The HPLC method was found to be simple, selective, precise, and reproducible for the estimation of both drugs from spiked human plasma.     

Liquid Chromatographic Analysis of Cephalexin in Human Plasma by Fluorescence Detection of the 9-Fluorenylmethyl Chloroformate Derivative

Abstract

A simple and sensitive precolumn derivatization method for the determination of cephalexin in human plasma has been developed. Cephalexin was derived with 9-fluorenylmethyl chloroformate (FMOC-Cl) in borate buffer (5 mM, pH 8.5) for 15 min at 25°C. Optimal conditions for the derivatization were described. The derivative was chromatographed on an XDB-C₁₈ column with water–acetonitrile (10:90, v/v) as mobile phase at a flow rate of 1.0 mL/min. The fluorescence excitation and emission wavelengths were 268 nm and 314 nm, respectively. The standard curve in spiked plasma was linear over the range of 0.0234–58.5 µg/mL; the detection limit (signal-to-noise ratio = 3; injection volume, 10 µL) was about 0.014 µg/mL. The performance of analysis was studied, and the validated method showed excellent performance in terms of selectivity, sensitivity, precision, and accuracy.     

Rapid determination and comparative pharmacokinetics of tetrahydropalmatine in spontaneously hypertensive rats and normotensive rats

A rapid high‐performance liquid chromatographic method was developed and validated for determination of tetrahydropalmatine (THP), an active component of Rhizoma Corydalis, in rat plasma. The samples were prepared using protein precipitation and separated on an Agilent XDB‐C₁₈ column (150 × 4.6 mm, 5 µm) with the mobile phase consisting of methanol–0.1% phosphate acid solution, adjusted with triethylamine to pH 5.5 (65:35). Good linearity was found within 0.10–10.00 µg/mL of THP in rat plasma sample. The intra‐ and inter‐day precision values were less than 10%. The developed method was successfully applied to assess the pharmacokinetics of THP in spontaneously hypertensive rats (SHR) and normotensive rats. After oral administration of a single dose of THP (60 mg/kg), the maximum plasma concentrations were 6.15 ± 2.1 and 7.54 ± 2.9 µg/mL for normotensive rats and SHR, respectively. The mean values of AUC_0–∞ of THP in SHR were 81.44 ± 45.0 µg h/mL, significantly higher (p < 0.05) than in normotensive rats (44.06 ± 19.6 µg h/mL). The t_1/2 and MRT in SHR were much longer than that in healthy Sprague–Dawley rats, indicating slow elimination of THP in SHR. The results indicated that there are some differences in pharmacokinetics of THP in SHR and Sprague–Dawley rats and it is very important to investigate the pharmacokinetic properties of drugs in pathological conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of Mycophenolic Acid (MPA) and Its Acyl and Phenol Glucuronide Metabolits Simultaneously in Human Plasma by a Simplified HPLC Method

Abstract

A simple HPLC method with ultraviolet detection for simultaneous determination of Mycophenolic acid (MPA), its phenol glucuronide metabolite (MPAG) and acyl‐MPAG (AcMPAG) in human plasma was established. The plasma samples were prepared with protein‐preciptaing reagent, and the supernatant was eluted on Zorbax column (250 mm×4.6 mm i.d, 5 µm) with 20 mmol/l NaH₂PO₄ buffer (pH 3.0, adjusted with 20% phosphoric acid) and methanol (45:55, v/v) at 304 nm. The column temperature was 45°C, and the flow rate was 1.2 ml/min. The assay was linear within the range of 0.2–50 µg/L for MPA (r=0.9997), 2.8–531 µg/L for MPAG (r=0.9999), and 0.3–24 µg/L for AcMPAG (r=0.9994). Mean absolute recovery of MPA and its metabolites and internal standard was >80%. The average recoveries of MPA, MPAG, and AcMPAG were 94.0–101.4, 98.4–101.9, and 96.1–104.2%, respectively. The RSD of within‐day and between‐day were all lower than 15%. The method described is sensitive, reproducible, and will be useful in TDM or pharmacokinetic studies of MPA.     

Estimation of Alprazolam and Sertraline in Pure Powder and Tablet Formulations by High-Performance Liquid Chromatography and High-Performance Thin-Layer Chromatography

Abstract

This article describes validated high-performance liquid chromatographic (HPLC) and high-performance thin-layer chromatographic (HPTLC) methods for simultaneous estimation of alprazolam (ALZ) and sertraline (SER) in pure powder and tablet formulation. The HPLC separation was achieved on a Nucleosil C18 column (150 mm long, 4.6 mm i.d., and 5-µm particle size) using acetonitrile and phosphate buffer (50 + 50 v/v), pH 5.5, as the mobile phase at a flow rate of 1.0 mL/min at ambient temperature. The HPTLC separation was achieved on an aluminum-backed layer of silica gel 60 F₂₅₄ using acetone/toluene/ammonia (6.0:3.0:1.0, v/v/v) as the mobile phase. Quantification with the HPLC method was achieved with ultraviolet (UV) detection at 230 nm over the concentration range 3–18 µg/mL for both drugs with mean recovery of 101.86 ± 0.21 and 100.57 ± 0.31% for ALZ and SER, respectively. Quantification in HPTLC was achieved with UV detection at 230 nm over the concentration range of 400–1400 ng/spot for both drugs with mean recoveries of 101.32 ± 0.15 and 100.38 ± 0.51% for ALZ and SER, respectively. These methods are rapid, simple, precise, sensitive, and are applicable for the simultaneous determination of ALZ and SER in pure powder and formulations.     

Development and Validation of Liquid Chromatography-Tandem Mass Spectrometry Method for Detection and Quantification of Flunisolide in Tissue Culture Medium

A robust, sensitive, and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method capable of quantifying flunisolide in the tissue culture matrix was developed and validated. Both flunisolide and dexamethasone (internal standard) were extracted from tissue culture medium, with 5% fetal bovine serum, 1% nonessential amino acids, and 1% penicillin/streptomycin by simple liquid–liquid extraction. The analytes were chromatographically separated (10 ng/mL for flunisolide) using a C8 column (4.6 mm × 150 mm; 5 µm particle size). The mobile phase was comprised of methanol:water (80:20 v/v). The analytes were separated at baseline within 2.5 min. using a flow rate of 1 mL/min. Mass spectrometry detection was carried out in negative atmospheric pressure chemical ionization mode. The calibration curves for the analyte were linear over the range of 10–200 ng/mL (R² ≥ 0.9968, n = 6). The inter and intra-batch mean percent accuracy ranged within 97.7–110.6% and the precision range was 3.5–10.4% (% coefficient of variation ≤15%). Stability studies revealed that the analyte was stable in the matrix for at least six hours at room temperature and at the end of three successive freeze and thaw cycles. The method reported here is specific for flunisolide quantification was also used in monolayer efflux assay using CaCo₂ cell lines, which will eventually aid P- glycoprotein transport studies for flunisolide.     

Liquid Chromatographic Determination of Glyoxal and Methylglyoxal from Serum of Diabetic Patients using Meso‐Stilbenediamine as Derivatizing Reagent

Abstract

Meso‐stilbenediamine has been used as derivatizing reagent for liquid chromatographic (LC) determination of glyoxal (Go), methylglyoxal (MGo), and dimethylglyoxal (DMGo) at pH 3. Liquid chromatographic elution and separation was carried out from the column Kromasil 100 C‐18, 5 µm (15×0.46 mm i.d.) with methanol: water:acetonitrile (59:40:1, v/v/v) with a flow rate of 1 mL/min and ultraviolet detection at 254 nm. The linear calibration curves were obtained for Go, MGo, and DMGo within 0.97–4.86 µg/mL, 1.52–7.6 µg/mL, and 1.41–7.08 µg/mL with detection limits of 48 ng/mL, 76 ng/mL, and 70.8 ng/mL, respectively. The method was applied for the determination of Go and MGo from serum of patients suffering from diabetes and ketosis. The amounts of Go and MGo found were 0.150–0.260 µg/mL and 0.160–0.270 µg/mL with coefficient of variation (C.V.) 2.6–4.7% and 2.5–4.6%, respectively. The results obtained were compared with normal subjects with Go and MGo contents of 0.025–0.065 µg/mL and 0.030–0.070 µg/mL with C.V 1.5–4.9% and 1.6–4.8% in the serum.     

Method development and validation for simultaneous determination of ebastine and its active metabolite carebastine in human plasma by liquid chromatography–tandem mass spectrometry and its application to a clinical pharmacokinetic study in healthy Chinese volunteers

A simple LC–tandem mass spectrometry (MS/MS) method to determine ebastine and carebastine (active metabolite) in human plasma was developed and validated. Analytes and internal standards were precipitated by protein precipitation and separated on Synergi Hydro-RP 80A column (4 μm, 50 mm × 2.0 mm; Phenomenex) by gradient elution with mobile phase A comprising 0.1% formic acid in 5 mm ammonium acetate (NH₄Ac) and B comprising 100% methanol at a flow rate 0.4 mL/min. Ions were detected in positive multiple reaction monitoring mode, and they exhibited linearity over concentration range 0.01–8.0 and 1.00–300 ng/mL for ebastine and carebastine, respectively. A clinical pharmacokinetic study was conducted in healthy Chinese volunteers under fasting and fed conditions after a single oral administration of 10 mg ebastine. The maximum plasma concentration (C_max), time to C_max (T_max) and elimination half-life for ebastine were 0.679 ± 0.762 ng/mL, 1.67 ± 1.43 h and 7.86 ± 6.18 h, respectively, whereas these for carebastine were 143 ± 68.4 ng/mL, 5.00 ± 2.00 h and 17.4 ± 4.97 h, respectively under fasting conditions; the corresponding values under fed conditions were 4.13 ± 2.53 ng/mL, 3.18 ± 1.09 h and 21.6 ± 7.77 h for ebastine and 176 ± 68.4 ng/mL, 6.14 ± 2.0 h and 20.0 ± 4.97 h for carebastine.     

Randomized two‐way cross‐over bioequivalence study of two amoxicillin formulations and inter‐ethnicity pharmacokinetic variation in healthy Malay volunteers

The objectives of this study were to develop a new deproteinization method to extract amoxicillin from human plasma and evaluate the inter‐ethnic variation of amoxicillin pharmacokinetics in healthy Malay volunteers. A single‐dose, randomized, fasting, two‐period, two‐treatment, two‐sequence crossover, open‐label bioequivalence study was conducted in 18 healthy Malay adult male volunteers, with one week washout period. The drug concentration in the sample was analyzed using high‐performance liquid chromatography (UV–vis HPLC). The mean (standard deviation) pharmacokinetic parameter results of Moxilen® were: peak concentration (C_max), 6.72 (1.56) µg/mL; area under the concentration–time graph (AUC_0–8), 17.79 (4.29) µg/mL h; AUC_0–∞, 18.84 (4.62) µg/mL h. Those of YSP Amoxicillin® capsule were: C_max, 6.69 (1.44) µg/mL; AUC_0–8, 18.69 (3.78) µg/mL h; AUC0_0–∞, 19.95 (3.81) µg/mL h. The 90% confidence intervals for the logarithmic transformed C_max, AUC_0–8 and AUC_0–∞ of Moxilen® vs YSP Amoxicillin® capsule was between 0.80 and 1.25. Both C_max and AUC met the predetermined criteria for assuming bioequivalence. Both formulations were well tolerated. The results showed significant inter‐ethnicity variation in pharmacokinetics of amoxicillin. The C_max and AUC of amoxicillin in Malay population were slightly lower compared with other populations. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of aromatic amines in environmental water samples using solid-phase extraction modified with sodium dodecyl sulphate and micellar liquid chromatography

Extraction and determination of seven aromatic amines in environmental water samples were performed with solid-phase extraction (SPE) and micellar liquid chromatography (MLC) using experimental design. Extraction of aromatic amines was carried out with a C₁₈ cartridge modified with sodium dodecyl sulphate (SDS). The washing solution and elution solvent for extraction of aromatic amines were aqueous solution containing 5% (v/v) acetonitrile and 5% (v/v) acetone and 3 mL methanol, respectively. The chemometrics approach was applied for the separation optimisation of these compounds using MLC. Different mobile phase compositions were used for modelling based on retention times to obtain the best separation using central composite design. The optimum mobile phase composition for separation and determination of analytes in water samples was 69 mM SDS, 9% v/v 1-propanol and pH = 6.4. Recoveries were between 84.8–93.5% with relative standard deviation (RSD) less than 5.8% (n = 5). Limits of detection and linear range were 1–4.5 and 3.1–125.0 µg/L, respectively. The proposed method was applied to determine the aromatic amines in real samples (river and well waters). Amount of 4-nitroaniline and 3-nitroaniline in river water sample were 2.15 and 1.91 µg/L, respectively.     

Enhanced HPLC‐MS/MS method for the quantitative determination of the co‐administered drugs ceftriaxone sodium and lidocaine hydrochloride in human plasma following an intramuscular injection and application to a pharmacokinetic study

A sensitive HPLC–MS/MS method was established for the quantification of ceftriaxone sodium (CFT) and lidocaine HCl (LDC) in human plasma utilizing cefixime (CFX) and tadalafil (TDA) as internal standards. The analytes were extracted from human plasma by protein precipitation using acetonitrile. Chromatographic separation was performed on Kinetex C₁₈ (50.0 × 4.6 mm, 5 μm particle size) column with methanol–0.01 M ammonium acetate pH 6.4 (70: 30, v/v) as mobile phase. Multiple reaction monitoring involving the transitions 555.10 → 396.20, 235.20 → 86.00, 454.20 → 284.80 and 390.20 → 268.20 was utilized to quantify CFT, LDC, CFX and TDA, respectively, using a triple quadrupole mass spectrometer which was operated in positive ion mode. The method revealed linearity in the concentration range of 3.0–300.0 μg/mL for CFT and 3.0–300.0 ng/mL for LDC. The validation of the method was achieved in accordance to the US Food and Drug Administration guidelines. A pharmacokinetic study was performed on healthy Egyptian volunteers after intramuscular injection of sterile ceftriaxone sodium (1 g CFT dissolved in 3.5 mL of 1% LDC) after approval from the ethics committee. The pharmacokinetic parameters were: C_max 141.15 ± 39.84 (μg/mL) and 55.02 ± 9.36 (ng/mL); t_max (h) 2.50 ± 0.50 and 1.5 ± 0.50; t_½ (h) 7.30 ± 2.98 and 4.23 ± 1.96; and K_el (h⁻¹) 0.10 ± 0.04 and 0.20 ± 0.13 for CFT and LDC, respectively.     

Development and Validation of Stability-Indicating HPLC Methods for Quantitative Determination of Pravastatin,Fluvastatin, Atorvastatin,and Rosuvastatin in Pharmaceuticals

Abstract

High-performance liquid-chromatographic (HPLC) methods were validated for determination of pravastatin sodium (PS), fluvastatin sodium (FVS), atorvastatin calcium (ATC), and rosuvastatin calcium (RC) in pharmaceuticals. Two stability-indicating HPLC methods were developed with a small change (10%) in the composition of the organic modifier in the mobile phase. The HPLC method for each statin was validated using isocratic elution. An RP-18 column was used with mobile phases consisting of methanol–water (60:40, v/v, for PS and RC and 70:30, v/v, for FVS and ATC). The pH of each mobile phase was adjusted to 3.0 with orthophosphoric acid, and the flow rate was 1.0 mL/min. Calibration plots showed correlation coefficients (r) > 0.999, which were calculated by the least square method. The detection limit (DL) and quantitation limit (QL) were 1.22 and 3.08 µg/mL for PS, 2.02 and 6.12 µg/mL for FVS, 0.44 and 1.34 µg/mL for ATC, and 1.55 and 4.70 µg/mL for RC. Intraday and interday relative standard deviations (RSDs) were <2.0%. The methods were applied successfully for quantitative determination of statins in pharmaceuticals.     

Design,synthesis of new novel quinoxalin-2(1H)-one derivatives incorporating hydrazone,hydrazine, and pyrazole moieties as antimicrobial potential with in-silico ADME and molecular docking simulation

A series of 6-(morpholinosulfonyl)quinoxalin-2(1H)-one based hydrazone, hydrazine, and pyrazole moieties were designed, synthesized, and evaluated for their in vitro antimicrobial activity. All the synthesized quinoxaline derivatives were characterized by IR, NMR (¹H /¹³C), and EI MS. The results displayed good to moderate antimicrobial potential against six bacterial, and two fungal standard strains. Among the tested derivatives, six quinoxalin-2(1H)-one derivatives 4a, 7, 8a, 11b, 13, and 16 exhibited a significant antibacterial activity with MIC values (0.97–62.5 µg/mL), and MBC values (1.94–88.8 µg/mL) compared with Tetracycline (MICs = 15.62–62.5 µg/mL, and MBCs = 18.74–93.75 µg/mL), and Amphotericin B (MICs = 12.49–88.8 µg/mL, and MFC = 34.62–65.62 µg/mL). In addition, according to CLSI standards, the most active quinoxalin-2(1H)-one derivatives demonstrated bactericidal and fungicidal behavior. Moreover, the most active quinoxaline derivatives showed a considerable antibacterial activity with bactericidal potential against multi-drug resistance bacteria (MDRB) strains with MIC values ranged between (1.95–15.62 µg/mL), and MBC values (3.31–31.25 µg/mL) near to standard Norfloxacin (MIC = 0.78–3.13 µg/mL, and MBC = 1.4–5.32 µg/mL. Further, in vitro S. aureus DNA gyrase inhibition activity were evaluated for the promising derivatives and displayed potency with IC₅₀ values (10.93 ± 1.81–26.18 ± 1.22 µM) compared with Ciprofloxacin (26.31 ± 1.64 µM). Interestingly, these derivatives revealed as good immunomodulatory agents by a percentage ranging between 82.8 ± 0.37 and 142.4 ± 0.98 %. Finally, some in silico ADME, toxicity prediction, and molecular docking simulation were performed and showed a promising safety profile with good binding mode.     

Veterinary antimicrobials and antiparasitics in fee-fishing ponds: analytical method and occurrence*

ABSTRACT

The aim of this work was to develop and validate a method using online solid-phase extraction and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry to determine residues of 22 veterinary drugs including sulfonamides, amphenicols, fluoroquinolones, benzimidazoles, trimethoprim (TMP) and oxytetracycline (OTC) in water from fee-fishing ponds. The optimal analytical conditions were as follows: XBridge C8 SPE column, Acquity UPLC CSH C18 analytical column, sample loading with water:methanol (98:2, v/v), mobile phase of water with 0.1% acetic acid:methanol (with gradient elution) and eluent flow rate of 0.3 mL min^?1. Quantification was performed in selected reaction monitoring mode and sulfadimethoxine-d₆, ciprofloxacin-d₈, florfenicol-d₃ and albendazole-d₃ were used as internal standards. Water samples collected from 11 fee-fishing ponds showed the presence of residues of FF (0.42–0.74 µg L^?1), albendazole (0.05–0.31 µg L^?1) and thiabendazole (0.45 µg L^?1). Thiamphenicol and TMP were detected at concentrations lower than the limits of quantification of the method (0.1 and 0.001 µg L^?1, respectively).     

Determination of Meserine,a new candidate for Alzheimer’s disease in mice brain by liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic and tissue distribution study

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of Meserine ((?)-meptazinol phenylcarbamate), a novel potent inhibitor of acetylcholinesterase (AChE), was developed, validated, and applied to a pharmacokinetic study in mice brain. The lower limit of quantification (LLOQ) was 1 ng mL^?1 and the linear range was 1–1,000 ng mL^?1. The analyte was eluted on a Zorbax SB-Aq column (2.1?×?100 mm, 3.5 μm) with the mobile phase composed of methanol and water (70:30, v/v, aqueous phase contained 10 mM ammonium formate and 0.3 % formic acid) using isocratic elution, and monitored by positive electrospray ionization in multiple reaction monitoring (MRM) mode. The flow rate was 0.25 mL min^?1. The injection volume was 5 μL and total run time was 4 min. The relative standard deviation (RSD) of intraday and interday variation was 2.49–7.81 and 3.01–7.67 %, respectively. All analytes were stable after 4 h at room temperature and 6 h in autosampler. The extraction recoveries of Meserine in brain homogenate were over 90 %. The main brain pharmacokinetic parameters obtained after intranasal administration were T _max?=?0.05 h, C _max?=?462.0?±?39.7 ng g^?1, T _1/2?=?0.4 h, and AUC_(0-∞)?=?283.1?±?9.1 ng h g^?1. Moreover, Meserine was distributed rapidly and widely into brain, heart, liver, spleen, lung, and kidney tissue. The method is validated and could be applied to the pharmacokinetic and tissue distribution study of Meserine in mice.     

Determination of sertraline in rat plasma by HPLC and fluorescence detection and its application to in vivo pharmacokinetic studies

A simple, rapid, and sensitive HPLC method based on 9H‐fluoren‐9‐ylmethyl chloroformate derivatization for the quantification of sertraline in rat plasma has been developed, requiring a plasma sample of only 0.1 mL, which was deproteinized and derivatized for 5 min in two single steps. The obtained derivative was stable at room temperature and was determined by HPLC using a fluorescence detector. The analytical column was a C(18) column and the mobile phase was acetonitrile and water (80:20, v/v). Calibration curves were linear in the range of 10–500 ng/mL. The limit of detection was approximately 3 ng/mL, and the lower limit of quantification was established at 10 ng/mL. The bias of the method was lower than 10%, and the within day as well as between day, relative standard deviations were lower than 12%. This analytical method was successfully applied to characterize sertraline pharmacokinetics in rats following intravenous (t_1/2 = 213 ± 48 min, Cl = 43.1 ± 8.7 mL/min, V_d = 11560 ± 1861 mL) and oral (C_max = 156 ± 76 ng/mL, t_max = 63.8 ± 16.3 min) administration of 2 and 5 mg, respectively.     

Chemical constituents of essential oil of endemic Rhanterium suaveolens Desf. growing in Algerian Sahara with antibiofilm,antioxidant and anticholinesterase activities

Twenty compounds were detected in the essential oil of Rhanterium suaveolens representing 98.01% of the total oil content. Perillaldehyde (45.79%), caryophyllene oxide (24.82%) and β-cadinol (5.61%) were identified as the main constituents. In β-carotene–linoleic acid assay, both the oil and the methanol extract exhibited good lipid peroxidation inhibition activity, with IC₅₀ values of 17.97 ± 5.40 and 11.55 ± 3.39 μg/mL, respectively. In DPPH and CUPRAC assays, however, the methanol extract exhibited a good antioxidant activity. The highest antibiofilm activity has been found 50.30% against Staphylococcus epidermidis (MU 30) at 20 μg/mL for essential oil and 58.34% against Micrococcus luteus (NRRL B-4375) at 25 mg/mL concentration for methanol extract. The in vitro anticholinesterase activity of methanol extract showed a moderate acetylcholinesterase inhibitory (IC₅₀ = 168.76 ± 0.62 μg/mL) and good butyrylcholinesterase inhibitory (IC₅₀ = 54.79 ± 1.89 μg/mL) activities. The essential oil was inactive against both enzymes.     

Determination of Nimesulide by Ion Pair High-Performance Liquid Chromatography Using Tetrabutylammonium as the Counterion

A new method for nimesulide was developed using ion-pair reversed phase liquid chromatography and tetrabutylammonium hydrogen sulfate as the ion-pairing reagent. The influence of the ion pair forming reagent concentration, pH, and mobile phase composition on the retention time of nimesulide were studied. The optimum experimental conditions included a C18 column, a mobile phase of a 50/50 (v/v) mixture of acetonitrile and 15 mM phosphate buffer (pH 8.00) containing 6 mM tetrabutylammonium hydrogen sulfate, 25°C, isocratic elution, a flow rate of 1 mL/min, a run time of 10 minutes, and photodiode array detection at 404 nm. From the analysis of the results, the mechanism for the separation of nimesulide was also established. The retention time for nimesulide was 4.76 ± 0.05 min. The method was linear between concentrations of 9 µg/mL to 64 µg/mL, with limits of detection and quantification of 1.111 µg/mL and 3.390 µg/mL, respectively. The method is simple, rapid, accurate, and precise, and successfully applied for the determination of nimesulide in pharmaceutical products.