High‐performance liquid chromatography tandem mass spectrometry method for quantification of endothelin receptor antagonist drug,ambrisentan, in human plasma and its application in a pharmacokinetic study

A simple and sensitive liquid chromatography tandem mass spectrometry method has been developed for the quantification of ambrisentan (AMB) in human plasma using midazolam (MID) as an internal standard (IS). Chromatographic separation was performed using a Beta Basic‐8 (50 × 4.6 mm, 5 µm) column with an isocratic mobile phase. AMB and MID were detected with proton adducts at m/z 379.09 → 303.12 and 326.15 → 291.14 in multiple reaction monitoring‐positive mode, respectively. A solid‐phase extraction method was used for extraction of the analyte and IS from the plasma samples. The method was shown to be reproducible and reliable with within‐run precision <11%, between‐run precision <14% and linear concentration range from 10.0 to 2000.2 ng/mL, with a correlation coefficient (r²) of >0.995. The method was successfully applied to a pharmacokinetic study of oral administration of AMB (10 mg) in 24 healthy Indian male human volunteers under fasting conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of four components in Baige capsule by HPLC: application to pharmacokinetics and tissue distribution of normal and middle cerebral artery occlusion rats

A sensitive and specific high‐performance liquid chromatography (HPLC) method was developed and applied to the pharmacokinetics for simultaneous identification and quantification of four components – puerarin, daidzein, imperatorin and isoimperatorin – in the plasma and tissues of normal and middle cerebral artery occlusion rats after oral administration of Baige capsule. Ferulic was used as the internal standard. The extraction procedure was composed of two independent steps. The plasma was prepared by liquid–liquid extraction with light petroleum–acetic ether (1:1, v/v) first and then protein was precipitated with methanol. The tissue samples were weighted and homogenated with normal saline, then the homogenate was prepared by liquid–liquid extraction and protein precipitation. The parameters of pharmacokinetics were calculated using DAS 2.1.1 software. The calibration curves of all four components in the plasma and tissue homogenates were in good linearity in the measured range with R² ≥ 0.9921. The relative standard deviation of the intra‐ and inter‐day accuracy at different levels was less than ±18.0%. In conclusion, the established method was a simple and effective one to simultaneously detect all four components in the plasma and tissues of rats, and was successfully applied in the pharmacokinetics of Baige capsule. Copyright © 2013 John Wiley & Sons, Ltd.     

LC‐ESI‐MS/MS analysis and pharmacokinetics of jolkinolide B,a potential antitumor active component isolated from Euphorbia fischeriana,in rat plasma

A simple, specific and reproducible liquid chromatography–electrospray ionization mass spectrometry was developed and validated for the determination of jolkinolide B, a potential antitumor active component isolated from Euphorbia fischeriana, in rat plasma. Chromatographic separation was achieved on a Venusil MP‐C₁₈ column using an isocratic elution. Jolkinolide B and osthole (internal standard) were monitored by positive electrospray ionization in the selected reaction monitoring mode. Good linearity (r² > 0.996) was achieved by a weighted (1/x²) linear least‐squares regression over a concentration range of 6.50–2600 ng/mL. The accuracy and precision of the assay were satisfactory and the method proved to be applicable to pharmacokinetics following a single intravenous bolus injection of jolkinolide B to rats. Copyright © 2013 John Wiley & Sons, Ltd.     

An HPLC method for the quantitation of 3‐pentylbenzo[c]thiophen‐1(3H)‐one in dog plasma and its application to a pharmacokinetic study

A simple, sensitive and reproducible high‐performance liquid chromatography (HPLC) assay method was developed for the estimation of 3‐pentylbenzo[c]thiophen‐1(3H)‐one (S₅), a potential anti‐ischemic stroke agent, in dog plasma. The analytical procedure involves protein precipitation of S₅ and nobiletin (internal standard) from dog plasma with acetonitrile. Chromatographic separation was achieved on Sapphire C18 analytical column with methanol–water (80:20, v/v) as mobile phase. The eluate was monitored using a UV detector set at 260 nm. The calibration curves were linear over the range of 0.2–20 µg/mL. Absolute recoveries of S₅ were 79.2–86.1% from dog plasma. The intra‐ and inter‐day relative standard deviation precisions were <7 and 5%, respectively. The method was successfully applied to the pharmacokinetic study of S₅ in beagle dogs. Copyright © 2014 John Wiley & Sons, Ltd.     

Nonvolatile salt‐free stabilizer for the quantification of polar imipenem and cilastatin in human plasma using hydrophilic interaction chromatography/quadrupole mass spectrometry with contamination sensitive off‐axis electrospray

A hydrophilic interaction chromatography/mass spectrometry (HILIC‐MS)‐based assay for imipenem (IMP) and cilastatin (CIL) was recently reported. This orthogonal electrospray ion source‐based (ORS) assay utilized nonvolatile salt (unremovable) to stabilize IMI in plasma. Unfortunately, this method was not applicable to conventional MS with off‐axis spray (OAS‐MS) because MS sensitivity was rapidly deteriorated by the nonvolatile salt. Therefore, we aimed to find a nonvolatile salt‐ and ion suppression‐free approach to stabilize and measure the analytes in plasma using OAS‐MS. Acetonitrile and methanol were tested to stabilize the analytes in the plasma samples. The recoveries, matrix effects and stabilities of the analytes in the stabilizer‐treated samples were studied. The variations in MS signal intensities were used as the indicator of the assay ruggedness. The results show that a mixture of methanol and acetonitrile (1:1) is best for the storage and measurement of IMP and CIL in human plasma. Utilization of this precipitant not only blocked the hydrolysis of the analytes in plasma but also resulted in an ion suppression‐free, fast (120 s per sample) and sensitive detection. The sensitivity obtained using the less sensitive OAS‐MS (API3000, 4 pg on column) is much greater than that of the published ORS‐MS‐based assay (API4000, 77 pg on column). The ruggedness of the assay was demonstrated by its constant MS signal intensity. In conclusion, an improved HILIC/MS‐based assay for IMP and CIL was established. The approach presented here provides a simple solution to the challenge of analyzing hydrolytically unstable β‐lactam antibiotics in biological samples. Copyright © 2013 John Wiley & Sons, Ltd.     

A new approach for pharmacokinetic studies of natural products: measurement of isoliquiritigenin levels in mice plasma,urine and feces using modified automated dosing/blood sampling system

The present study was undertaken to investigate the pharmacokinetics of isoliquiritigenin (isoLQ) as determined by the automated dosing/blood sampling (ABS) and traditional manual blood sampling techniques in awake and freely moving mice using combined liquid chromatography tandem mass spectrometry. Pharmacokinetic comparison was conducted by allocating mice into two groups; an ABS group (intravenous study and oral studies, n = 5 each) and a manual group (intravenous and oral studies; n = 5 each). Significant differences in pharmacokinetic parameters (area under the curve and clearances) were observed between ABS and manual groups. This could be mainly due to the blood sampling site difference (via heart puncture in traditional manual group and via carotid artery in ABS groups). The low F of isoLQ could be mainly due to a considerable gastrointestinal and/or hepatic first‐pass effect and not to incomplete absorption. The driving force for distribution and elimination of drugs is its concentration in the arterial blood. Therefore, the ABS method was found to be a useful drug development tool for accelerating the process of preclinical in vivo studies and for obtaining reliable and accurate pharmacokinetic parameters in mice. Copyright © 2013 John Wiley & Sons, Ltd.     

Development and validation of a UPLC‐MS/MS method for the determination of 7‐hydroxymitragynine,a μ‐opioid agonist,in rat plasma and its application to a pharmacokinetic study

A simple, sensitive and specific ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method was developed and validated to determine the concentrations of 7‐hydroxymitragynine in rat plasma. Following a single‐step liquid–liquid extraction of plasma samples using chloroform, 7‐hydroxymitragynine and the internal standard (tryptoline) were separated on an Acquity UPLC^TM BEH C₁₈ (1.7 µm, 2.1 × 50 mm) column using an isocratic elution at a flow rate of 0.2 mL/min. The mobile phase consisted of 0.1% acetic acid in water and 0.1% acetic acid in acetonitrile (10:90, v/v). The run time was 2.5 min. The analysis was carried out under the multiple reaction‐monitoring mode using positive electrospray ionization. Protonated ions [M + H]⁺ and their respective product ions were monitored at the following transitions: 415 → 190 for 7‐hydroxymitragynine and 173 → 144 for the internal standard. The calibration curve was linear over the range of 10–4000 ng/mL (r² = 0.999) with a lower limit of quantification of 10 ng/mL. The extraction recoveries ranged from 62.0 to 67.3% at concentrations of 20, 600 and 3200 ng/mL). Intra‐ and inter‐day assay precisions (relative standard deviation) were <15% and the accuracy was within 96.5–104.0%. This validated method was successfully applied to quantify 7‐hydroxymitragynine in rat plasma following intravenous administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Development of a new UPLC‐MSMS method for the determination of temozolomide in mice: application to plasma pharmacokinetics and brain distribution study

A sensitive and accurate liquid chromatography method with mass spectrometry detection was developed and validated for the quantification of temozolomide in mouse plasma and brain. Theophyllin was used as the internal standard. A single‐step protein precipitation was used for plasma and brain sample preparation. The method was validated with respect to selectivity, extraction recovery, linearity, intra‐ and inter‐day precision and accuracy, limit of quantification and stability. The method has a limit of quantification of 50 ng/mL for temozolomide in plasma and 125 ng/g in brain. This method was used successfully to perform brain and plasma pharmacokinetic studies of temozolomide in mice after intraperitoneal administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly sensitive method for the determination of a novel triple kinase inhibitor with anti‐cancer activity,JI‐101, in rat plasma by liquid chromatography–electrospray ionization tandem mass spectrometry: application to a pharmacokinetic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of JI‐101 in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The assay procedure involves extraction of JI‐101 and phenacetin (internal standard, IS) from rat plasma with a solid‐phase extraction process. Chromatographic separation was achieved using a binary gradient using mobile phase A (acetonitrile) and B (0.2% formic acid in water) at a flow rate of 0.30 mL/min on a Prodigy ODS column with a total run time of 4.0 min. The MS/MS ion transitions monitored were 466.1 → 265 for JI‐101 and 180.1 → 110.1 for IS. Method validation and sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 5.03 ng/mL and the linearity range extended from 5.03 to 2014 ng/mL. The intra‐day and inter‐day precisions were in the ranges of 1.17–19.6 and 3.09–10.4%, respectively. This method has been applied to a pharmacokinetic study of JI‐101 in rats. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination and pharmacokinetics of periplocin in rat plasma by LC‐MS

A simple and sensitive LC‐MS method for the determination of periplocin in rat plasma was developed and validated. The chromatographic separation was carried out using a reverse‐phase Kromasil C₁₈ column(150 × 4.6 mm, i.d., 5 µm) with a mobile phase composed of methanol–water (76:24, v/v). The flow rate of mobile phase was 0.8 mL/min. The calibration curve was linear within the concentration range 1–1000 ng/mL. The intra‐ and inter‐day precisions across three validation days over the entire concentration range was lower than 9.2% in terms of relative standard deviation. Accuracy determined at three quality control concentrations ranged from ?2.0 to 6.0% in terms of relative error. The validated method was applied to the pharmacokinetic study of periplocin in rat plasma after intravenous and intramuscular administration. Copyright © 2010 John Wiley & Sons, Ltd.