Liquid chromatography‐tandem mass spectrometric method for determination of E121 in mouse plasma and its application to pharmacokinetics

A rapid LC‐MS/MS method for quantification of an enaminone analog, E121 in mouse plasma using E118 as an internal standard (IS) has been developed and validated. The analyte was analyzed on C₁₈ column using a mobile phase of acetonitrile/methanol/ammonium acetate/formic acid (60:20:20:0.025, v/v/v/v) at a flow rate of 0.25 mL/min. Quantitation was achieved using ESI+ interface, employing MRM mode at m/z 308>262 and 222>194 for E121 and IS, respectively. The calibration standards were linear over a range of 0.10–20 μg/mL (r²>0.99) with an LLOQ of 0.1 μg/mL (RSD%; 11.4% and bias%; 9.5%). Intra‐ and inter‐run precision of E121 assay ranged from 3.7 to 10.9% with accuracy (bias) that varied between ?10.0 and 12.0%, demonstrating good precision and accuracy. Recoveries of E121 and the IS from plasma were above 80%. Stability of E121 in plasma showed that the analyte was stable under various conditions. The matrix effect study showed a lack of effect. The applicability of the developed method was demonstrated by measuring E121 in mouse plasma samples following intraperitoneal administration of various doses ranging from 10 to 100 mg/kg and this study demonstrates that E121 exhibits linear kinetics in the dose range studied.     

Quantification of mequitazine in human plasma by gas chromatography– quadrupole mass spectrometry and its application to a human pharmacokinetic study

A specific and sensitive gas chromatography–mass spectrometry (GC‐MS) with quadrupole mass analyzer type was developed and validated for the quantitative analysis of mequitazine in human plasma. After liquid–liquid extraction of plasma samples containing mequitazine and promethazine (internal standard, IS) using hexane with pH adjustment, the extract was evaporated and an aliquot of reconstituted residue was injected into the GC‐MS system. The assay showed linearity over a concentration range from 1 to 50 ng/mL. Intra‐ and inter‐day precision for mequitazine was <9.09 and 9.29%, respectively, and intra‐ and inter‐day accuracy ranged from ?7.97 to 9.05% and from ?1.51 to 7.89%, respectively. The lower limit of quantification was 1 ng/mL in the present assay. The developed analytical method was successfully applied to a pharmacokinetic study after a single oral administration of mequitazine in human subjects. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of PM00104, a novel antineoplastic agent, in mouse, rat, dog, and human plasma

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay was developed and validated to quantify a novel antineoplastic agent, PM00104, in mouse, rat, dog, and human plasma. The method was validated to demonstrate the specificity, limit of quantification (LOQ), accuracy, and precision of measurements. The calibration range for PM00104 was established using PM00104 standards from 0.01-5.0 ng/mL in blank plasma. The selected reaction monitoring (SRM), based on the m/z 692.2 --> 218.2 transition, was specific for PM00104, and that based on the m/z 697.2 --> 218.2 transition was specific for PM00104 ((13)C(2),(2)H(3)) (the internal standard, IS); no endogenous materials interfered with the analysis of PM00104 and IS from blank plasma. The assay was linear over the concentration range 0.01-5.0 ng/mL. The correlation coefficients for the calibration curves ranged from 0.9981-0.9999. The mean intra-day and inter-day accuracies for all calibration standards (n = 8) ranged from 97-105% (< or =5% bias) in human plasma, and the mean inter-day precision for all calibration standards was less than 8.5%. The mean intra- and inter-day assay accuracy for all quality control (QC) replicates in human plasma (n = 9), determined at each QC level throughout the validated runs, ranged from 96-112% (< or =12% bias) and from 102-105% (< or =5% bias), respectively. The mean intra- and inter-day assay precision was less than 15.0 and 11.8% for all QC levels, respectively. For the QC samples prepared in animal species plasma, the %CV values of the assays ranged from 1.8-8.8% in mouse plasma, from 3.7-13.8% in rat plasma, and from 3.0-7.2% in dog plasma. The assay accuracies ranged from 92-102% (< or =8% bias) for all QC levels prepared in mouse plasma; ranged from 93-106% (< or =7% bias) in rat plasma; and ranged from 95-114% (< or =14% bias) in dog plasma. The assay has been used to support preclinical pharmacokinetic and toxicokinetic studies and is currently used to measure PM00104 plasma concentrations to support clinical trials.     

Validated LC‐MS method for simultaneous quantitation of catalpol and harpagide in rat plasma: application to a comparative pharmacokinetic study in normal and diabetic rats after oral administration of Zeng‐Ye‐Decoction

A simple and efficient liquid chromatography‐mass spectrometry (LC‐MS) method was developed and validated for simultaneous quantitation of catalpol and harpagide in normal and diabetic rat plasma. Protein precipitation extraction with acetonitrile was carried out using salidroside as the internal standard (IS). The LC separation was performed on an Elite C₁₈ column (150 × 4.6 mm, 5 µm) with the mobile phase consisting of acetonitrile and water within a runtime of 12.0 min. The analytes were detected without endogenous interference in the selected ion monitoring mode with positive electrospray ionization. Calibration curves offered satisfactory linearity (r > 0.99) at linear range of 0.05–50.0 µg/mL for catalpol and 0.025–5.0 µg/mL for harpagide with the lower limits of quantitation of 0.05 and 0.025 µg/mL, respectively. Intra‐ and inter‐day precisions (RSD) were <9.4%, and accuracy (RE) was in the ?6.6 to 4.9% range. The extraction efficiencies of catalpol, harpagide and IS were all >76.5% and the matrix effects of the analytes ranged from 86.5 to 106.0%. The method was successfully applied to the pharmacokinetic study of catalpol and harpagide after oral administration of Zeng‐Ye‐Decoction to normal and diabetic rats, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of the neuropharmacological drug nodakenin in rat plasma and brain tissues by liquid chromatography tandem mass spectrometry: Application to pharmacokinetic studies

A rapid and sensitive liquid chromatography tandem mass spectrometry detection using selected reaction monitoring in positive ionization mode was developed and validated for the quantification of nodakenin in rat plasma and brain. Pareruptorin A was used as internal standard. A single step liquid–liquid extraction was used for plasma and brain sample preparation. The method was validated with respect to selectivity, precision, accuracy, linearity, limit of quantification, recovery, matrix effect and stability. Lower limit of quantification of nodakenin was 2.0 ng/mL in plasma and brain tissue homogenates. Linear calibration curves were obtained over concentration ranges of 2.0–1000 ng/mL in plasma and brain tissue homogenates for nodakenin. Intra‐day and inter‐day precisions (relative standard deviation, RSD) were <15% in both biological media. This assay was successfully applied to plasma and brain pharmacokinetic studies of nodakenin in rats after intravenous administration.     

Determination of swertianolin in rat plasma by LC‐MS/MS and its application to a pharmacokinetic study

A sensitive and rapid LC‐MS/MS method has been developed and validated for quantifying swertianolin in rat plasma using rutin as an internal standard (IS). Following liquid–liquid extraction with ethyl acetate, chromatographic separation for swertianolin was achieved on a C₁₈ column with a gradient elution using 0.1% formic acid as mobile phase A and acetonitrile as mobile phase B at a flow rate of 0.3 mL/min. The detection was performed on a tandem mass spectrometer using multiple reaction monitoring via an electrospray ionization source and operating in the negative ionization mode. The optimized mass transition ion pairs (m/z) for quantitation were 435.1/272.0 for swertianolin and 609.2/300.1 for IS. The lower limit of quantitation was 0.5 ng/mL within a linear range of 0.5–500 ng/mL. Intra‐day and inter‐day precision was less than 6.8%. The accuracy was in the range of ?13.9 to 12.0%. The mean recovery of swertianolin was >66.7%. The proposed method was successfully applied in evaluating the pharmacokinetics of swertianolin after an oral dose of 50 mg/kg Swertia mussotii extract in rats. Copyright © 2014 John Wiley & Sons, Ltd.     

LC–ESI–MS/MS determination of copanlisib,a novel PI3K inhibitor,in mouse plasma and its application to a pharmacokinetic study in mice

A sensitive, selective and rapid LC–ESI–MS/MS method has been developed and validated for the quantification of copanlisib in mouse plasma using enasidenib as an internal standard (IS) as per regulatory guideline. Copanlisib and the IS were extracted from mouse plasma using ethyl acetate as an extraction solvent and chromatographed using an isocratic mobile phase (0.2% formic acid–acetonitrile; 25:75, v/v) on a HyPURITY C₁₈ column. Copanlisib and the IS eluted at ~0.95 and 2.00 min, respectively. The MS/MS ion transitions monitored were m/z 481.1 → 360.1 and m/z 474.0 → 456.0 for copanlisib and the IS, respectively. The calibration range was 3.59–3588 ng/mL. The intra‐ and inter‐batch accuracy and precision (RE and RSD) across quality controls met the acceptance criteria. Stability studies showed that copanlisib was stable in mouse plasma for one month. This novel method has been applied to a pharmacokinetic study in mice.     

Development of a method for the determination of cefovecin in plasma by HPLC

A simple high‐performance liquid chromatography method for the determination of cefovecin in small volume plasma has been developed. Following solid‐phase extraction using Oasis HLB cartridges, samples were separated by reverse‐phase high‐performance liquid chromatography on an XBridge C₈ (3.5 µm) 4.6 × 250 mm column and quantified using ultraviolet detection at 280 nm. The mobile phase was a mixture of 10 mm ammonium acetate (pH 3.5) and acetonitrile (89:11), with a flow rate of 0.85 mL/min. The standard curve ranged from 0.1 to 200 µg/mL. Intra‐ and Inter‐assay variability for cefovecin was <10%, and the average recovery was >90%. The lower limit of quantitation was 0.1 µg/mL. This method was successfully applied to the analysis of cefovecin samples at our institution. This is also the first fully validated method with an internal standard that does not use mass spectrometry. Copyright © 2014 John Wiley & Sons, Ltd.     

Fast and parallel determination of PCB 77 and PCB 180 in plasma using ultra performance liquid chromatography with diode array detection: A pharmacokinetic study in Swiss albino mouse

A simple, sensitive and reproducible ultra‐performance liquid chromatography (UPLC) method has been developed and validated for simultaneous estimation of polychlorinated biphenyl (PCB) 77 and PCB 180 in mouse plasma. The sample preparation was performed by simple liquid–liquid extraction technique. The analytes were chromatographed on a Waters Acquity H class UPLC system using isocratic mobile phase conditions at a flow rate of 0.3 mL/min and Acquity UPLC BEH shield RP₁₈ column maintained at 35°C. Quantification was performed on a photodiode array detector set at 215 nm and PCB 101 was used as internal standard (IS). PCB 77, PCB 180, and IS retention times were 2.6, 4.7 and 2.8 min, respectively, and the total run time was 6 min. The method was validated for specificity, selectivity, recovery, linearity, accuracy, precision and sample stability. The calibration curve was linear over the concentration range 10–3000 ng/mL for PCB 77 and PCB 180. Intra‐ and inter‐day precisions for PCBs 77 and 180 were found to be good with CV <4.64%, and the accuracy ranged from 98.90 to 102.33% in mouse plasma. The validated UPLC method was successfully applied to the pharmacokinetic study of PCBs 77 and 180 in mouse plasma.     

UPLC‐MS/MS assay for the simultaneous quantification of carvedilol and its active metabolite 4′‐hydroxyphenyl carvedilol in human plasma to support a bioequivalence study in healthy volunteers

An ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method has been developed for the simultaneous determination of carvedilol and its pharmacologically active metabolite 4′‐hydroxyphenyl carvedilol in human plasma using their deuterated internal standards (IS). Samples were prepared by solid‐phase extraction using 100 μL human plasma. Chromatographic separation of analytes was achieved on UPLC C18 (50 × 2.1 mm, 1.7 µm) column using acetonitrile‐4.0 mm ammonium formate, pH 3.0 adjusted with 0.1% formic acid (78:22, v/v) as the mobile phase. The multiple reaction monitoring transitions for both the analytes and IS were monitored in the positive electrospray ionization mode. The method was validated over a concentration range of 0.05–50 ng/mL for carvedilol and 0.01‐10 ng/mL for 4′‐hydroxyphenyl carvedilol. Intra‐ and inter‐batch precision (% CV) and accuracy for the analytes varied from 0.74 to 3.88 and 96.4 to 103.3% respectively. Matrix effect was assessed by post‐column analyte infusion and by calculation of precision values (coefficient of variation) in the measurement of the slope of calibration curves from eight plasma batches. The assay recovery was within 94–99% for both the analytes and IS. The method was successfully applied to support a bioequivalence study of 12.5 mg carvedilol tablets in 34 healthy subjects. Copyright © 2013 John Wiley & Sons, Ltd.     

HPLC method for determination of DRF-4367 in rat plasma: validation and its application to pharmacokinetics in Wistar rats

A specific, accurate, precise and reproducible high-performance liquid chromatography (HPLC) method was developed for the estimation of DRF-4367, a novel cyclooxygenase-2 inhibitor in rat plasma. The assay procedure involved simple liquid/liquid extraction of DRF-4367 and internal standard (IS, celecoxib) from plasma into dichloromethane. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100-5C(18) column (4.6 x 250 mm, 5 microm). The mobile phase consisting of 0.01 M potassium dihydrogen ortho-phosphate (pH 3.2) and acetonitrile (40:60, v/v) was used at a flow rate of 1.0 mL/min. The eluate was monitored using an UV detector set at 247 nm. The ratio of peak area of analyte to IS was used for quantification of plasma samples. Nominal retention times of DRF-4367 and IS were 6.6 and 11.2 min, respectively. The standard curve for DRF-4367 was linear (r(2) > 0.999) in the concentration range 0.1-20 micro g/mL. Absolute recovery was >86% from rat plasma for both analyte and IS. The lower limit of quantification of DRF-4367 was 0.1 micro g/mL. The inter- and intra-day precisions in the measurement of quality control samples, 0.1, 0.3, 8.0 and 15.0 microg/mL, were in the range 6.93-9.34% relative standard deviation (RSD) and 0.48-6.59% RSD, respectively. Accuracy in the measurement of QC samples was in the range 91.24-109.36% of the nominal values. Analyte and IS were stable in the battery of stability studies, viz. benchtop, autosampler and freeze-thaw cycles. Stability of DRF-4367 was established for 1 month at -80 degrees C. The application of the assay to a pharmacokinetic study in rats is described.     

Simultaneous determination of linarin,naringenin and formononetin in rat plasma by LC‐MS/MS and its application to a pharmacokinetic study after oral administration of Bushen Guchi Pill

A sensitive and reproducible liquid chromatography tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the simultaneous determination of linarin, naringenin and formononetin in rat plasma after addition of sulfamethoxazole as the internal standard (IS). Separation was carried out on a Diamonsil C₁₈ column (150 × 4.6 mm, 5 µm) with liner gradient elution using methanol (A) and 0.5‰ formic acid aqueous solution (B). Detection was performed on a triple‐quadrupole linear ion trap mass spectrometer with the negative ion electrospray ionization in multiple‐reaction monitoring (MRM) mode. The MRM transitions were m/z 591.2 → 283.2, 271.0 → 150.9, 266.9 → 252.0 and 252.0 → 155.9 for linarin, naringenin, formononetin and IS, respectively. All analytes showed good linearity within the concentration range (r > 0.9973). The lower limits of quantitation of linarin, naringenin and formononetin were 0.64, 1.07 and 1.04 ng/mL, respectively. Intra‐day and inter‐day precisions of the investigated components exhibited an RSD within 9.96%, and the accuracy (relative error) ranged from ?11.25 to 9.38% at all quality control levels. The developed method was successfully applied to a pharmacokinetic study of linarin, naringenin and formononetin in rats after oral administration of Bushen Guchi Pill. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantitative determination of ragaglitazar in rat plasma by HPLC: validation and application in pharmacokinetic study

A specific, accurate, precise and reproducible high-performance liquid chromatography (HPLC) method was developed for the estimation of ragaglitazar [(-) DRF 2725, NNC 61-0029], a novel anti-diabetic agent, in rat plasma. The assay procedure involved simple liquid/liquid extraction of ragaglitazar and internal standard (IS, troglitazone) from plasma into ethyl acetate. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100 - 5C(18) column (4.6 x 250 mm, 5 micro m). Mobile phase consisting of 0.01 M potassium dihydorgen ortho phosphate (pH 3.2) and acetonitrile (30:70, v/v) was used at a flow rate of 1.0 mL/min. The eluate was monitored using an UV detector set at 240 nm. Ratio of peak area of analyte to IS was used for quantification of plasma samples. Nominal retention times of IS and ragaglitazar were 6.9 and 12.2 min, respectively. The standard curve for ragaglitazar was linear (r(2) > 0.999) in the concentration range 0.2-100 micro g/mL. Absolute recovery was >87% from rat plasma for both analyte and IS. The lower limit of quantification (LLOQ) of ragaglitazar was 0.2 micro g/mL. The inter- and intra-day precision in the measurement of quality control (QC) samples, 0.2, 1.0, 5.0 and 50 micro g/mL, were in the range 1.32-3.70% relative standard deviation (RSD) and 1.19-9.39% RSD, respectively. Accuracy in the measurement of QC samples was in the range 94.28-107.45%. Analyte and IS were stable in the battery of stability studies, viz. benchtop, autosampler and freeze/thaw cycles. Stability of ragaglitazar was established for 1 month at -20 degrees C. The application of the assay to a pharmacokinetic study in rats is described.     

Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of PM02734, a novel antineoplastic agent, in dog plasma

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay was developed and validated to quantify a novel antineoplastic agent, PM02734, in dog plasma. The method was validated to demonstrate the specificity, limit of quantification (LOQ), accuracy, and precision of measurements. The calibration range for PM02734 was established using PM02734 standards from 0.05 to 100 ng/mL in blank plasma. The dominating ions were doubly charged molecular ions [M+2H]2+ at m/z 740.0 instead of singly charged ones at m/z 1478.4. The selected reaction monitoring (SRM), based on the m/z 740.0 --> 212.2 transition, was specific for PM02734, and that based on the m/z 743.8 --> 212.2 transition was specific for deuterated PM02734 (the internal standard, IS); no endogenous materials interfered with the analysis of PM02734 and IS from blank plasma. The assay was linear over the concentration range 0.05-100 ng/mL. In terms of sensitivity of assay 0.05 ng/mL is a very low LLOQ, especially considering PM02734 is a peptide. The correlation coefficients for the calibration curves ranged from 0.9990 to 0.9999. The mean intraday and interday accuracies for all calibration standards (n = 9) ranged from 93 to 111% (< or =11% bias) in dog plasma, and the mean interday precision for all calibration standards was less than 6.4%. The mean intra- and interday assay accuracy for all quality control replicates in dog plasma (n = 9), determined at each QC level throughout the validated runs, ranged from 85-111% (< or =15% bias) and from 99-109% (< or =9% bias), respectively. The mean intra- and interday assay precision was less than 12.1 and 13.3% for all QC levels, respectively. The assay has been used to support preclinical pharmacokinetic (PK) and toxicokinetic studies. The results showed that preclinical samples could be monitored for PM02734 up to 168 h after dosing, which allowed us to identify multiple elimination phases and accurately estimate PK information.     

Development of an LC–MS/MS method for quantification of two pairs of isomeric flavonoid glycosides and other ones in rat plasma: Application to pharmacokinetic studies

A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of six flavonoid glycosides – isoorientin ( 1 ), orientin ( 2 ), 2″‐O‐β ‐d ‐xylopyranosyl isoorientin ( 3 ), 2″‐O‐β ‐d ‐xylopyranosyl isovitexin ( 4 ), 6‐C‐l ‐α ‐arabipyranosyl vitexin ( 5 ) and vitexin ( 6 ) – in rat plasma using isoquercitrin as the internal standard (IS). Plasma samples were prepared by a one‐step protein precipitation with acetonitrile. Chromatographic analysis was carried out on a 25 cm C₁₈ column with a gradient mobile phase consisting of acetonitrile and 0.1% aqueous formic acid. Six analytes and IS were detected through electrospray ionization in negative‐ion selection reaction monitoring mode. The mass transitions were as follows: m/z 447.2 → 327.0 for 1 , m/z 447.2 → 327.0 for 2 , m/z 579.3 → 458.9 for 3 , m/z 563.0 → 293.1 for 4 , m/z 563.0 → 353.0 for 5 , m/z 431.1 → 311.1 for 6 , and m/z 463.1 → 300.2 for IS. Calibration curves exhibited good linearity (r ² > 0.9908) over a wide concentration range for all compounds. Intra‐ and inter‐day precision (RSD, %) at four different levels were both <14.2% and the accuracy (RE, %) ranged from −11.9 to 12.0%. The extraction recoveries of the six components ranged from 88.2 to 103.6%. The validated assay was successfully applied to the pharmacokinetic studies of the six components in male rat plasma after intravenous administration of total flavonoids of Scorzonera austriaca Wild.     

Development and validation of a sensitive LC‐MS/MS‐ESI method for the determination of ivabradine in human plasma: application to a pharmacokinetic study

A sensitive, rapid assay method for estimating ivabradine in human plasma has been developed and validated using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The procedure involved extraction of ivabradine and the internal standard (IS) from human plasma by solid‐phase extraction. Chromatographic separation was achieved using an isocratic mobile phase (0.1% formic acid–methanol, 60:40, v/v) at a flow rate of 1.0 mL/min on an Aglient Eclipse XDB C₈ column (150 × 4.6 mm, 5 µm; maintained at 35°C) with a total run time of 4.5 min. Detection was achieved using an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 3200 triple‐quadrupole mass spectrometer. The MS/MS ion transitions monitored were 469–177 for ivabradine and 453–177 for IS. Method validation was performed according to Food and Drug Administration guidelines, and the results met the acceptance criteria. The calibration curve was linear over a concentration range of 0.1–200 ng/mL. The lower limit of quantitation achieved was 0.1 ng/mL. Intra‐ and inter‐day precisions were in the range of 1.23–14.17% and 5.26‐8.96%, respectively. Finally, the method was successfully used in a pharmacokinetic study that measured ivabradine levels in healthy volunteers after a single 5 mg oral dose of ivabradine. Copyright © 2013 John Wiley & Sons, Ltd.     

Rapid analysis of neurotransmitters in rat brain using ultra‐fast liquid chromatography and tandem mass spectrometry: application to a comparative study in normal and insomnic rats

Neurotransmitters and their metabolites in central nervous system were known to play a significant role in sedation and hypnosis. A rapid and sensitive UFLC‐MS/MS method for simultaneous determination of serotonin, 5‐hydroxyindole acetic acid (5‐HIAA), tryptophan (Try), dopamine (DA), norepinephrine (NE), γ‐aminobutyric acid (GABA), glutamic acid (Glu) and acetylcholine (Ach) in rat brain without derivatization, ion‐pairing reagent or pre‐concentration was developed. Analytes and IS were separated on a Inertsil ODS‐EP column (150 mm × 4.6 mm, 5 µm particles) and analyzed in a single chromatographic run in less than 9.0 min, using gradient elution with the mobile phase consisting of methanol and 0.01% acetic acid in water at a flow rate of 1.2 ml min^?1. The detection of the analytes was performed on 4000Q UFLC‐MS/MS system with turbo ion spray source in positive ion and multiple reaction monitoring mode. The developed method provided excellent linear calibration curves for the assay of analytes (R² ≥ 0.9915). Limits of quantification were in the range of 1.0 ng ml^?1 to 1.0 µg ml^?1 for the analytes in rat brain. Intra‐ and inter‐day precision and accuracy of analytes were well within acceptance criteria (15%). Mean extraction recoveries of analytes and IS from rat brain were all more than 80.0%. Furthermore, the validated method was successfully applied to comparing profiles of analytes in normal and insomnic rat brains. Results indicated that there were statistically significant differences for serotonin, 5‐HIAA, DA, NE, Glu and Ach, but no significant difference for Try and GABA between two groups. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantification of taraxasterol in rat plasma by LC/MS/MS: application to a pharmacokinetic study

Taraxasterol, a pentacyclic triterpene from Taraxacum officinale, is one of the main active constituents of the herb. This study developed and validated a highly selective and sensitive liquid chromatography/tandem mass spectrometry for the determination of taraxasterol in rat plasma over the range of 9.0–5000 ng/mL. Chromatographic separation was achieved on a C₁₈ (4.6 × 50 mm, 5.0 µm) column with methanol–isopropanol–water–formic acid (80:10:10:0.1, v/v/v/v) as mobile phase with an isocratic elution. The flow rate was 0.7 mL/min. After adding cucurbitacin IIa as an internal standard (IS), liquid–liquid extraction was used for sample preparation using ethyl acetate. The atmospheric pressure chemical ionization source was applied and operated in positive ion mode. Selected reaction monitoring mode was used for the quantification of transition ions m/z 409.4 → 137.1 for taraxasterol and m/z 503.4 → 113.1 for IS. The mean recoveries of taraxasterol in rat plasma ranged from 85.3 to 87.2%. The matrix effects for taraxasterol were between 98.5 and 104.0%. Intra‐ and inter‐day precision were both <11.8%, and the accuracy of the method ranged from ?7.0 to 12.9%. The method was successfully applied to a pharmacokinetic study of taraxasterol after oral administration of 7.75, 15.5 and 31.0 mg/kg in rats. Copyright © 2015 John Wiley & Sons, Ltd.     

Study on pharmacokinetics and tissue distribution of pteryxin in mice by ultra-pressure liquid chromatography with tandem mass spectrometry

Pteryxin is a coumarin compound naturally occurring in the roots of Radix Peucedani, a commonly used as traditional Chinese medicine for the treatment of certain respiratory diseases and hypertension. An UPLC‐MS/MS method was established to quantify pteryxin in mouse plasma and tissue homogenates. Isoimperatorin was used as internal standard (IS). The method was based on protein precipitation with methanol for sample preparation. Pteryxin and IS were separated using a UPLC? BEH C₁₈ column and eluted with a mobile phase consisting of methanol and water (70:30, v/v) at a flow‐rate of 0.2 mL/min. MS/MS detection was carried out by monitoring the fragmentation of m/z 409.3–287.2 for pteryxin and m/z 271.3–185.2 for IS on a triple‐quadrupole mass spectrometer. The total run time was only 6 min. The results showed that it had good linearity over a wide concentration range (r > 0.999), and pteryxin was rapidly distributed and then eliminated from mouse plasma (t_1/2 =1.463 h). The major distribution tissues of pteryxin in mice were liver, and pteryxin was enabled to cross the blood–brain barrier owing to its low polarity. There was no long‐term accumulation of pteryxin in mouse tissues. Copyright © 2011 John Wiley & Sons, Ltd.