A rapid and simple RP‐HPLC method for quantification of kirenol in rat plasma after oral administration and its application to pharmacokinetic study

A rapid and simple reverse‐phase high‐performance liquid chromatography (RP‐HPLC) was developed and validated for the quantification of kirenol in rat plasma after oral administration. Kirenol and darutoside (internal standard, IS) were extracted from rat plasma using Cleanert™ C₁₈ solid‐phase extraction (SPE) cartridge. Analysis of the extraction was performed on a Thermo ODS‐2 Hypersil C₁₈ reversed‐phase column with a gradient eluent composed of acetonitrile and 0.1% phosphoric acid. The flow rate was 1.0 mL/min and the detection wavelength was set at 215 nm. The calibration curve was linear over the range of 9.756–133.333 µg/mL (r² = 0.9991) in rat plasma. The lower limits of detection and quantification were 2.857 and 9.756 µg/mL, respectively. The intra‐ and inter‐day precisions (relative standard deviation, RSD) were between 2.24 and 4.46%, with accuracies ranging from 91.80 to 102.74%. The extraction recovery ranged from 98.16 to 107.62% with RSD less than 4.81%. Stability studies showed that kirenol was stable in preparation and analytical process. The present method was successfully applied to the pharmacokinetic study of kirenol in male Sprague–Dawley rats after oral administration at a dose of 50 mg/kg. Copyright © 2010 John Wiley & Sons, Ltd.     

A reliable method of liquid chromatography for the quantification of acetaminophen and identification of its toxic metabolite N-acetyl-p-benzoquinoneimine for application in pediatric studies

The aim of the present study was to develop a simple, selective and reliable method to quantify acetaminophen and its toxic metabolite N‐acetyl‐p‐benzoquinoneimine (NAPQI) for pediatric studies using 100 µL plasma samples, by reverse‐phase HPLC and UV detection. The assay was performed using a C₁₈ column and an isocratic elution with water–methanol–formic acid (70:30:0.15; v/v/v) as mobile phase. Linearity of the method was assayed in the range of 1–30 µg/mL for acetaminophen and 10–200 µg/mL for NAPQI, with a correlation coefficient r = 0.999 for both compounds, and inter‐ and intra‐day coefficients of variation of less than 13%. Several commonly co‐administered drugs were analyzed for selectivity and no interference with the determinations was observed. The detection and quantification limits for acetaminophen and NAPQI were 0.1 and 1 µg/mL, and 0.1 and 10 µg/mL respectively. The present method can be used to monitor acetaminophen levels using 100 µL plasma samples, which may be helpful when very small samples need to be analyzed, as in pharmacokinetics determination or drug monitoring in plasma in children. This assay is also able to detect the NAPQI for drug monitoring in patients diagnosed with acetaminophen intoxication. Copyright © 2010 John Wiley & Sons, Ltd.     

Stability‐indicating ultra‐performance liquid chromatography method for the estimation of thymoquinone and its application in biopharmaceutical studies

Thymoquinone (THQ) is known for its neuroprotective and anti‐convulsant properties in preclinical studies. We herewith describe a simple, rapid, selective, sensitive and stability‐indicating UPLC method for the estimation of THQ and its application to biopharmaceutical studies such as in vitro release from nanoparticulate system and in vivo pharmacokinetic study. The method employed gradient elution using a Waters Acquity HSS‐T3 C₁₈ (100 × 2.1 mm, 1.8 µm) UPLC column. The mobile phase consisted of water and acetonitrile, pumped at a flow rate of 0.5 mL/min. The injection volume was 5 µL and THQ was monitored at 294 nm wavelength with a total run time of 6 min. In solution as well as in plasma, the method was found to be linear (r ≥ 0.998), precise (CV ≤ 2.45%) and accurate (recovery ≥ 84.8%) in the selected concentration range of 0.1–0.8 µg/mL. Forced degradation studies revealed that THQ undergoes degradation under acidic, basic, oxidation and UV light stress conditions. However, the developed UPLC method could effectively resolve degradation product peaks from THQ. Further, no interference was found at the retention time of THQ from any plasma components, indicating selectivity of the developed method. For solutions, the limits of detection and quantitation of the method were found to be 0.001 and 0.0033 µg/mL, respectively; while in plasma they were 0.006 and 0.02 µg/mL, respectively. The validated method was successfully applied to quantify THQ in dissolution medium as well as oral in vivo pharmacokinetic study of THQ suspension and THQ‐ solid lipid nanoparticle (THQ‐SLN) formulation. A 2‐fold increase in the relative bioavailability was observed with the THQ‐SLN compared with THQ. The results indicate that the SLN significantly increased plasma concentrations and retention within the systemic circulation. Copyright © 2010 John Wiley & Sons, Ltd.     

Measurement of quetiapine and four quetiapine metabolites in human plasma by LC-MS/MS

There is interest in monitoring plasma concentrations of N‐desalkylquetiapine in relation to antidepressant effect. A simple LC‐MS/MS method for quetiapine and four metabolites in human plasma (50 μL) has been developed to measure concentrations of these compounds attained during therapy. Analytes and internal standard (quetiapine‐d8) were extracted into butyl acetate–butanol (10:1, v/v) and a portion of the extract analysed by LC‐MS/MS (100 × 2.1 mm i.d. Waters Spherisorb S5SCX; eluent: 50 mmol/L methanolic ammonium acetate, pH* 6.0; flow‐rate 0.5 mL/min; positive ion APCI‐SRM, two transitions per analyte). Assay calibration (human plasma calibrators) was linear across the ranges studied (quetiapine and N‐desalkylquetiapine 5–800, quetiapine sulfoxide 100–15,000, others 2–100 µg/L). Assay validation was as per FDA guidelines. Quetiapine sulfone was found to be unstable and to degrade to quetiapine sulfoxide. In 47 plasma samples from patients prescribed quetiapine (prescribed dose 200–950 mg/day), the (median, range) concentrations found (µg/L) were: quetiapine 83 (7–748), N‐desalkylquetiapine, 127 (7–329), O‐desalkylquetiapine 12 (2–37), 7‐hydroxyquetiapine 3 (<1–48), and quetiapine sulfoxide 3,379 (343–21,704). The analyte concentrations found were comparable to those reported by others except that the concentrations of the sulfoxide were markedly higher. The reason for this discrepancy in unclear. Copyright © 2012 John Wiley & Sons, Ltd.     

Simultaneous determination of norisoboldine and its major metabolite in rat plasma by ultra-performance liquid chromatography-mass spectrometry and its application in a pharmacokinetic study

Norisoboldine (NIB) is one of the main bioactive isoquinoline alkaloids in Linderae Radix. A rapid, selective and sensitive method using UPLC‐ESI/MS was first developed for simultaneous determination of NIB and norisoboldine‐9‐O‐α‐glucuronide (NIB‐Glu), its major metabolite in rat plasma. A one‐step protein precipitation with methanol was employed as sample preparation technique. Chromatographic separation was carried out on an Acquity UPLC BEH C₁₈ column (50 × 2.1 mm, i.d. 1.7 µm) with a gradient mobile phase consisting of acetonitrile and water containing 0.1% formic acid. Detection and quantification were performed using a quadrupole mass spectrometer by selective ion reaction‐monitoring mode. Good linearity was achieved using weighted (1/x²) least squares linear regression over the concentration ranges 0.01–2 µg/mL for NIB and 0.025–25 µg/mL for NIB‐Glu. The lower limit of quantification of NIB and NIB‐Glu was 0.01 and 0.025 µg/mL, respectively. The intra‐ and inter‐day precisions (relative standard deviations) of the assay at all three quality control levels were 4.6–14.1% for NIB, and 5.0–12.2% for NIB‐Glu. The accuracies (relative error) were −13.5–8.1% for NIB and −12.8–7.6% for NIB‐Glu, respectively. This developed method was successfully applied to an in vivo pharmacokinetic study in rats after a single intravenous dose of 10 mg/kg NIB. Copyright © 2010 John Wiley & Sons, Ltd.     

A validated HPLC‐PDA method for identification and quantification of two bioactive alkaloids,ephedrine and cryptolepine,in different Sida species

A simple, rapid, accurate and reproducible reverse‐phase HPLC method has been developed for the identification and quantification of two alkaloids ephedrine and cryptolepine in different extracts of Sida species using photodiode array detection. Baseline separation of the two alkaloids was achieved on a Waters RP‐18 X‐terra column (250 × 4.6 mm, 5 µm) using a solvent system consisting of a mixture of water containing 0.1% Trifluoroacetic acid (TFA) and acetonitrile in a gradient elution mode with detection at 210 and 280 nm for ephedrine and cryptolepine, respectively. The calibration curves were linear in a concentration range of 10–250 µg/mL for both the alkaloids with correlation coefficient values >0.99. The limits of detection and quantification for ephedrine and cryptolepine were 5 and 10 µg/mL and 2.5 and 5 µg/mL, respectively. Relative standard deviation values for intra‐day and inter‐day precision were 1.22 and 1.04% for ephedrine and 1.71 and 2.06% for cryptolepine, respectively. Analytical recovery ranged from 92.46 to 103.95%. The developed HPLC method was applied to identify and quantify ephedrine and cryptolepine in different extracts of Sida species. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantitative determination of bioactive alkaloids lysergol and chanoclavine in Ipomoea muricata by reversed-phase high-performance liquid chromatography

A rapid, simple, sensitive, gradient and reproducible, reverse‐phase high‐performance liquid chromatographic method was developed for the quantitative estimation of bioactive alkaloids, lysergol and chanoclavine in the seeds of Ipomoea muricata. The clavine alkaloid, lysergol, is a bioenhancer for the drugs and nutrients. The samples were analyzed by reverse‐phase chromatography on a Waters spherisorb ODS2 column (250 × 4.6 mm, i.d., 10 µm) using binary gradient elution with acetonitrile and 0.01 m phosphate buffer (NaH₂PO₄) containing 0.1% glacial acetic acid at a flow rate of 0.8 mL/min, a column temperature of 25 °C and UV detection at λ 254 nm. The limits of detection (LOD) and quantitation (LOQ) were 0.035 and 0.106 µg/mL for lysergol and 0.039 and 0.118 µg/mL for chanoclavine, respectively. Standard curves were linear in the range of 2–10 µg/mL (r > 99) for both analytes. Good results were achieved with respect to repeatability (RSD < 2%) and recovery (99.20–102.0). The method was validated for linearity, accuracy repeatability, LOQ and LOD. The method is simple, accurate and precise, and may be recommended for routine quality control analysis of I. muricata seed extracts containing these two clavine alkaloids (1, 2) as bioactive principles of the herb. Copyright © 2011 John Wiley & Sons, Ltd.     

A chiral liquid chromatography method for the simultaneous determination of oxcarbazepine, eslicarbazepine, R-licarbazepine and other new chemical derivatives BIA 2-024, BIA 2-059 and BIA 2-265, in mouse plasma and brain

Recently, in silico models have been developed to predict drug pharmacokinetics. However, before application, they must be validated and, for that, information about structurally similar reference compounds is required. A chiral liquid chromatography method with ultraviolet detection (LC‐UV) was developed and validated for the simultaneous quantification of BIA 2–024, BIA 2–059, BIA 2–265, oxcarbazepine, eslicarbazepine (S‐licarbazepine) and R‐licarbazepine in mouse plasma and brain. Compounds were extracted by a selective solid‐phase extraction procedure and their chromatographic separation was achieved on a LiChroCART 250–4 ChiraDex column using a mobile phase of water–methanol (92:8, v/v) pumped at 0.7 mL/min. The UV detector was set at 235 nm. Calibration curves were linear (r² ≥ 0.996) over the concentration ranges of 0.2–30 µg/mL for oxcarbazepine, eslicarbazepine and R‐licarbazepine; 0.2–60 µg/mL for the remaining compounds in plasma; and 0.06–15 µg/mL for all the analytes in brain homogenate. Taking into account all analytes at these concentration ranges in both matrices, the overall precision did not exceed 9.09%, and the accuracy was within ±14.3%. This LC‐UV method is suitable for carrying out pharmacokinetic studies with these compounds in mouse in order to obtain a better picture of their metabolic pathways and biodistribution. Copyright © 2011 John Wiley & Sons, Ltd.     

A simple and sensitive HPLC-UV method for the determination of ponicidin in rat plasma and its application in a pharmacokinetic study

A simple, rapid, selective and sensitive HPLC‐UV method has been developed and validated for the determination of ponicidin in rat plasma. The analyte was extracted from rat plasma by liquid–liquid extraction with ethyl acetate as the extraction solvent. The LC separation was performed on a Zorbax Eclipse XDB C₁₈ analytical column (150 × 4.6 mm i.d., 5 µm) with an isocratic mobile phase consisting of methanol–water–phosphoric acid (45:55:0.01, v/v/v) at a flow rate of 1.0 mL/min. There was a good linearity over the range of 0.1–25 µg/mL (r = 0.9995) with a weighted (1/C²) least square method. The lower limit of quantification was proved to be 0.1 µg/mL. The accuracy was within ±10.0% in terms of relative error and the intra‐ and inter‐day precisions were less than 9.1% in terms of relative standard deviation. After validation, the method was successfully applied to characterize the pharmacokinetics of ponicidin in rats. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of a novel paclitaxel derivative (NPD‐103) in human plasma by ultra‐performance liquid chromatography–tandem mass spectrometry

A sensitive and specific ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS‐MS) method for quantification of a newly developed anticancer agent NPD‐103 has been established. An aliquot of human plasma sample (200 µL) was spiked with ¹³C‐labeled paclitaxel (internal standard) and extracted with 1.3 mL of tert‐butyl methyl ether. NPD‐103 was quantitated on a C₁₈ column with methanol–0.1% formic acid (75:25, v/v) as mobile phase using UPLC‐MS‐MS operating in positive electrospray ionization mode with a total run time of 3.0 min. For NPD‐103 at the concentrations of 1.0, 5.0 and 10.0 µg/mL in human plasma, the absolute extraction recoveries were 95.58, 102.43 and 97.77%, respectively. The linear quantification range of the method was 0.1–20.0 µg/mL in human plasma with linear correlation coefficients greater than 0.999. The intra‐ and inter‐day accuracy for NPD‐103 at 1.0, 5.0 and 10.0 µg/mL levels in human plasma fell into the ranges of 95.29–100.00% and 91.04–94.21%, and the intra‐ and inter‐day precisions were in the ranges of 8.96–11.79% and 7.25–10.63%, respectively. This assay is applied to determination of half‐life of NPD‐103 in human plasma. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative determination of sauchinone in rat plasma by liquid chromatography-mass spectrometry

A rapid, sensitive and specific method using liquid chromatography with tandem mass spectrometric detection (LC‐MS) was developed for the analysis of sauchinone in rat plasma. Di‐O‐methyltetrahydrofuriguaiacin B was used as internal standard (IS). Analytes were extracted from rat plasma by liquid–liquid extraction using ethyl acetate. A 2.1 mm i.d. × 150 mm, 5 µm, Agilent Zorbax SB‐C₁₈ column was used to perform the chromatographic analysis. The mobile phase was methanol–deionized water (80:20, v/v). The chromatographic run time was 7 min per injection and the flow‐rate was 0.2 mL/min. The tandem mass spectrometric detection mode was achieved with electrospray ionization interface in positive‐ion mode (ESI⁺). The m/z ratios [M + Na]⁺, m/z 379.4 for sauchinone and m/z 395.4 for IS were recorded simultaneously. Calibration curve were linear over the range of 0.01–5 µg/mL. The lowest limit of quantification was 0.01 µg/mL. The intra‐day and inter‐day precision and accuracy of the quality control samples were 2.94–9.42% and 95.79–108.05%, respectively. The matrix effect was 64.20–67.34% and the extraction recovery was 93.28–95.98%. This method was simple and sensitive enough to be used in pharmacokinetic research for determination of sauchinone in rat plasma. Copyright © 2011 John Wiley & Sons, Ltd.     

Development and validation of UPLC tandem mass spectrometry assay for separation of a phase II metabolite of ramipril using actual study samples and its application to a bioequivalence study

In this paper, we present a validated UPLC‐MS/MS assay for determination of ramipril and ramiprilat from human plasma samples. The assay is capable of isolating phase II metabolites (acylglucornides) of ramipril from in vivo study samples which is otherwise not possible using conventional HPLC conditions. Both analytes were extracted from human plasma using solid‐phase extraction technique. Chromatographic separation of analytes and their respective internal standards was carried out using an Acquity UPLC BEH C₁₈ (2.1 × 100 mm), 1.7 µm column followed by mass spectrometric detection using an Waters Quattro Premier XE. The method was validated over the range 0.35–70.0 ng/mL for ramipril and 1.0–40.0 ng/mL for ramiprilat. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of a novel nonfluorinated quinolone,nemonoxacin, in human feces and its glucuronide conjugate in human urine and feces by high‐performance liquid chromatography–triple quadrupole mass spectrometry

Three methods were developed and validated for determination of nemonoxacin in human feces and its major metabolite, nemonoxacin acyl‐β‐ d ‐glucuronide, in human urine and feces. Nemonoxacin was extracted by liquid–liquid extraction in feces homogenate samples and nemonoxacin acyl‐β‐ d ‐glucuronide by a solid‐phase extraction procedure for pretreatment of both urine and feces homogenate sample. Separation was performed on a C₁₈ reversed‐phase column under isocratic elution with the mobile phase consisting of acetonitrile and 0.1% formic acid. Both analytes were determined by liquid chromatography–tandem mass spectrometry with positive electrospray ionization in selected reaction monitoring mode and gatifloxacin as the internal standard. The lower limit of quantitation (LLOQ) of nemonoxacin in feces was 0.12 µg/g and the calibration curve was linear in the concentration range of 0.12–48.00 µg/g. The LLOQ of the metabolite was 0.0010 µg/mL and 0.03 µg/g in urine and feces matrices, while the linear range was 0.0010–0.2000 µg/mL and 0.03–3.00 µg/g, respectively. Validation included selectivity, accuracy, precision, linearity, recovery, matrix effect, carryover, dilution integrity and stability, indicating that the methods can quantify the corresponding analytes with excellent reliability. The validated methods were successfully applied to an absolute bioavailability clinical study of nemonoxacin malate capsule. Copyright © 2014 John Wiley & Sons, Ltd.     

Validation of a sensitive LC/MS/MS method for the determination of telaprevir and its R‐isomer in human plasma

The purpose of this study was to validate a reversed‐phase high‐performance liquid chromatographic (HPLC), tandem mass spectrometry (MS/MS) assay for the determination of telaprevir and its R‐diastereomer (VRT‐127394) in acidified and nonacidified human plasma. The chromatographic baseline separation of telaprevir and telaprevir‐R was performed on a Waters XBridge^TM BEH Shield C₁₈, 2.1 × 75 mm column with a 2.5 µm particle size, under isocratic conditions consisting of a mobile phase of 50:45:5 water–acetonitrile–isopropanol with 1% ammonia at 0.2 mL/min. This method utilized a stable isotope internal standard with 11 deuterium atoms on the structure of the telaprevir molecule (telaprevir‐d11). An internal standard for the telaprevir‐R (telaprevir‐R‐d11) was also prepared by incubating telaprevir‐d11 in basic solution, which facilitated isomer inter‐conversion. The detection and quantitation of telaprevir, telaprevir‐R, telaprevir‐IS and telaprevir‐R‐IS was achieved by positive ion electrospray (ESI+) MS/MS detection. The assay quantifiable limit was 5.0 ng/mL when 0.100 mL of acidified human plasma was extracted. Accuracy and precision were validated over the calibration range of 5.0–5000 ng/mL. It was demonstrated using patient samples that, contrary to previous recommendations, quantitation of telaprevir does not require acidified plasma. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of baicalin,oroxylin A‐7‐O‐glucuronide and wogonoside in rat plasma by UPLC‐DAD and its application in pharmacokinetics of pure baicalin,Radix Scutellariae and Yinhuang granule

A novel UPLC‐DAD method was developed and validated for the simultaneous determination of baicalin (baicalein‐7‐glucuronide, BG), oroxylin A‐7‐O‐glucuronide (OAG) and wogonoside (WG) in rat plasma using rutin as the internal standard. Plasma samples were precipitated using acetonitrile containing 0.1% formic acid. Separation was performed on an Agilent Eclipse Plus C₁₈ column (2.1 × 50 mm, 1.8 µm) using gradient acetonitrile and 0.2% formic acid water solution as mobile phase. The flow‐rate was set at 0.4 mL/min and the eluate was detected at 275 nm. The method was linear over the ranges of 0.075–17.50, 0.050–12.60 and 0.056–14.10 µg/mL for BG, OAG and WG, respectively. The intra‐ and inter‐day precisions were respectively <4.8% and 6.4%. All of the limits of detection of three analytes in rat plasma were 0.01 µg/mL, whereas the limits of quantification were, respectively, 0.035, 0.025 and, 0.025 µg/mL. This assay has been successfully applied to pharmacokinetics of BG, OAG and WG in rats after oral administration of Yinhuang granule (YHG) and comparative pharmacokinetics of BG in rats following oral administration of the pure BG, Radix Scutellariae (RS) or YHG. We speculate that some co‐existing ingredients in RS or YHG may increase the absorption and elimination of BG in rat. This work may be helpful for the quality control of Yinhuang granule. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of a liquid chromatography assay for the determination of opicapone and BIA 9–1079 in rat matrices

Opicapone is a novel potent, reversible and purely peripheral third generation catechol‐O‐methyltransferase inhibitor, currently under clinical trials as an adjunct to levodopa therapy for Parkinson's disease. To support additional nonclinical pharmacokinetic studies, a novel high‐performance liquid chromatographic method coupled to a diode array detector (HPLC‐DAD) to quantify opicapone and its active metabolite (BIA 9–1079) in rat plasma and tissues (liver and kidney) is herein reported. The analytes were extracted from rat samples through a deproteinization followed by liquid‐liquid extraction. Chromatographic separation was achieved in less than 10 min on a reversed‐phase C₁₈ column, applying a gradient elution program with 0.05 M monosodium phosphate solution (pH 2.45 ± 0.05) and acetonitrile. Calibration curves were linear (r² ≥ 0.994) within the ranges of 0.04‐6.0 µg/mL for both analytes in plasma, 0.04‐4.0 µg/mL for opicapone in liver and kidney homogenates, and 0.07‐4.0 µg/mL and 0.06‐4.0 µg/mL for BIA 9–1079 in liver and kidney homogenates, respectively. The overall intra‐ and inter‐day accuracy ranged from ?12.68% to 7.70% and the imprecision values did not exceed 11.95%. This new HPLC‐DAD assay was also successfully applied to quantify opicapone and BIA 9–1079 in a preliminary pharmacokinetic study. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Comparative pharmacokinetics study of a kaurane diterpenoid after oral administration of monomer and Siegesbeckiae pubescens Makino extract to rats

In this paper, a sensitive, rapid and reproducible high‐performance liquid chromatography–tandem mass spectrometry method was developed to analyze 16α‐hydro‐ent‐kauran‐17,19‐dioic acid in rat plasma. First, this study compared the pharmacokinetics of 16α‐hydro‐ent‐kauran‐17,19‐dioic acid after oral administration of monomer and Siegesbeckiae pubescens Makino extract in rat plasma with approximately the same dosage of 6.0 mg/kg. Second, chromatographic separation was performed on a Waters Symmetry C₁₈ column (2.1 × 100 mm, 3.5 µm) with isocratic elution using methanol–water containing 5 mmol/L ammonium acetate (70:30, v/v) as mobile phase at a flow rate of 0.2 mL/min. The calibration curves were linear over the range of 30–12000 ng/mL for monomer. At different time points (0, 0.083, 0.25, 0.75, 1, 2, 4, 6, 8, 12, 18, 24, 36, 48, 60 and 72 h) after administration, the concentrations of monomer in rat plasma were determined and main pharmacokinetic parameters were estimated. The double absorption presented in this study indicates that the pharmacokinetics of monomer in rat plasma have significant differences between different groups. Copyright © 2013 John Wiley & Sons, Ltd.     

A rapid and sensitive LC‐MS/MS method for the determination of linarin in small‐volume rat plasma and tissue samples and its application to pharmacokinetic and tissue distribution study

A rapid and sensitive LC‐MS/MS method was developed for the determination of linarin in small‐volume rat plasma and tissue sample. Sample preparation was employed by the combination of protein precipitation (PPT) and liquid–liquid extraction (LLE) to allow measurement over a 5‐order‐of‐magnitude concentration range. Fast chromatographic separation was achieved on a Hypersil Gold column (100 × 2.1 mm i.d., 5 µm). Mass spectrometric detection was achieved using a triple‐quadrupole mass spectrometer equipped with an electrospray ionization interface operating in positive ionization mode. Quantification was performed using selected reaction monitoring of precursor‐product ion transitions at m/z 593 → 285 for linarin and m/z 447 → 271 for baicalin (internal standard). The total run time was only 2.8 min per sample. The calibration curves were linear over the concentration range of 0.4–200 µg/mL for PPT and 0.001–1.0 µg/mL for LLE. A lower limit of quantification of 1.0 ng/mL was achieved using only 20 μL of plasma or tissue homogenate. The intra‐ and inter‐day precisions in all samples were ≤14.7%, while the accuracy was within ±5.2% of nominal values. The validated method has been successfully applied to pharmacokinetic and tissue distribution study of linarin. Copyright © 2015 John Wiley & Sons, Ltd.     

Development and validation of a UPLC–MS method for the determination of galantamine in guinea pig plasma and its application to a pre‐clinical bioavailability study of novel galantamine formulations

To evaluate the bioavailability and pharmacokinetic profiles of two novel galantamine formulations as medical countermeasure products, an ultra‐performance liquid chromatography–single quadrupole mass spectrometry (UPLC–MS) method was developed and validated for quantifying galantamine in guinea pig plasma using solid‐phase extraction with a mixed mode strong cation exchange reversed‐phase cartridge. Chromatographic separation was achieved on a Waters Acquity UPLC BEH C₁₈ column maintained at 40°C. The mobile phases were solution A, acetonitrile–water, 5:95 (v/v) and solution B, acetonitrile–water 90:10 (v/v), both containing 2 mM ammonium formate and 0.2% formic acid. The mobile phase was delivered utilizing a 3 min gradient program start with 95%A–5%B at a flow rate of 0.6 mL/min. The analyte and internal standard, galantamine‐d3, were detected by selected ion monitoring mode on a Waters 3100 single quadrupole mass spectrometer with positive electrospray ionization. The method was validated according to the US Food and Drug Administration bioanalytical guidance. The method was selective and was linear over the analytical range of 2–2000 ng/mL. Accuracy and precision were acceptable with intra‐ and inter‐day accuracies between 96.8 and 101% and precisions (RSD) <4.88%. The method was successfully implemented to measure galantamine plasma levels in a series of pre‐clinical bioavailability studies for the evaluation of novel galantamine formulations.