Simultaneous determination of evodiamine and its four metabolites in rat plasma by LC–MS/MS and its application to a pharmacokinetic study

A simple and sensitive liquid chromatography tandem mass spectrometry method was validated for simultaneous quantification of evodiamine and its metabolites 10‐hydroxyevodiamine (M1), 18‐hydroxyevodiamine (M2), 10‐hydroxyevodiamine‐glucuronide (M3) and 18‐hydroxy‐ evodiamine‐glucuronide (M4) in rat plasma for the first time. The analytes were extracted with acetonitrile and separated on a C₁₈ column within 3 min. The detection was achieved in positive selected reaction monitoring mode with precursor‐to‐product transitions at m/z 304.1 → 161.1 for evodiamine, m/z 320.1 → 134.1 for M1, m/z 320.1 → 150.1 for M2, m/z 496.2 → 134.1 for M3, m/z 496.2 → 171.1 for M4 and m/z 349.2 → 305.1 for camptothecin (internal standard). The linearity was evident over the tested concentration ranges with correlation coefficients >0.9991. The lower limits of quantification for evodiamine, M1, M2, M3 and M4 were 0.1, 0.1, 0.1, 0.25 and 0.25 ng mL⁻¹, respectively. Extraction recoveries and matrix effects of the analytes were within the ranges of 84.51–97.21 and 90.13–103.30%, respectively. The accuracy (relative error) ranged from −8.14 to 7.23% while the intra‐ and inter‐day precisions (relative standard deviation) were < 9.31%. The validated assay was successfully applied for the pharmacokinetic study of evodiamine, M1, M2, M3 and M4 in rat. The current study will be helpful in understanding the in vivo disposition of evodiamine.     

Development and validation of LC–MS/MS method for amlexanox in rat plasma and its application in preclinical pharmacokinetics

Amlexanox, an anti-inflammatory and anti-allergic agent, has been widely used clinically for the treatment of canker sores, asthma, and allergic rhinitis. Recently, amlexanox has received considerable attention in curing nonalcoholic fatty liver diseases and hepatitis virus infection. Herein, we first established a sensitive high-performance liquid chromatography-tandem mass spectrum (LC–MS/MS) method for the determination of amlexanox in rat plasma. Propranolol was used as the internal standard (IS). Using a simple protein precipitation method, the amlexanox and IS were separated with Capcell Pak C18 column (2.0 × 50 mm, 5 μm) and eluted with water and acetonitrile each containing 0.1% formic acid using gradient elution condition at a flow rate of 0.4 mL·min⁻¹. Amlexanox and IS were detected by a triple quadrupole mass in multiple reactive monitoring (MRM) under the transitions of m/z 299.2 → 281.2 and m/z 259.9 → 116.1 with positive electrospray ionization, respectively. The calibration curves of amlexanox were established with the range of 50 to 2000 ng·mL⁻¹ (r² > 0.99). The validation method consisted of selectivity, accuracy, precision, carryover effect, matrix effect, recovery, dilution effect, and stability. The fully validated method was successfully applied to the pharmacokinetic study of amlexanox in Wistar rats.     

Development and validation of HPLC‐MS/MS method for the determination of lixivaptan in mouse plasma and its application in a pharmacokinetic study

The aim of the present study was to develop a simple, sensitive and accurate liquid chromatography–electrospray ionization tandem mass spectrometry (ESI‐MS/MS) method for the determination of lixivaptan (LIX) in mouse plasma using vildagliptin as the internal standard (IS). A precipitation procedure was used for the extraction of LIX and vildagliptin from mouse plasma. Chromatographic separation of LIX was achieved using a C₁₈ analytical column (50 × 2.1 mm, 1.8 μm) at 25°C. The mobile phase comprised acetonitrile and ammonium formate (10 mm , pH 3.1; 40:60, v /v) pumped at a flow rate of 0.3 mL min⁻¹. A tandem mass spectrometer with an electrospray ionization source was used to perform the assay. Quantification of LIX at m/z 290 → 137 and IS at 154 → 97 was attained through multiple reaction monitoring. The investigated method was authenticated following the bio‐analytical method of validation guidelines of the US Food and Drug Administration. The developed method showed a good linearity over the concentration range from 5 to 500 ng mL⁻¹, and the calibration curve was linear (r = 0.9998). The mean recovery of LIX from mouse plasma was 99.2 ± 0.68%. All validation parameters for LIX were within the levels required for acceptance. The proposed method was effectively used for a pharmacokinetic study of LIX in mouse plasma.     

Development and validation of a simple,sensitive and accurate LC‐MS/MS method for the determination of guanfacine,a selective α2A‐adrenergicreceptor agonist,in plasma and its application to a pharmacokinetic study

A simple, practical, accurate and sensitive liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and fully validated for the quantitation of guanfacine in beagle dog plasma. After protein precipitation by acetonitrile, the analytes were separated on a C₁₈ chromatographic column by methanol and water containing 0.1% (v/v) formic acid with a gradient elution. The subsequent detection utilized a mass spectrometry under positive ion mode with multiple reaction monitoring of guanfacine and enalaprilat (internal standard) at m/z 246.2 → 159.0 and m/z 349.2 → 205.9, respectively. Good linearity was obtained over the concentration range of 0.1–20 ng/mL for guanfacine in dog plasma and the lower limit of quantification of this method was 0.1 ng/mL. The intra‐ and inter‐day precisions were <10.8% relative standard deviation with an accuracy of 92.9–108.4%. The matrix effects ranged from 89.4 to 100.7% and extraction recoveries were >90%. Stability studies showed that both analytes were stable during sample preparation and analysis. The established method was successfully applied to an in vivo pharmacokinetic study in beagle dogs after a single oral dose of 4 mg guanfacine extended‐release tablets. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of GDC‐0980 (apitolisib), a small molecule dual phosphatidylinositide 3‐kinase/mammalian target of rapamycin inhibitor in dog plasma by LC‐MS/MS to support a GLP toxicology study

An LC‐MS/MS method for the determination of GDC‐0980 (apitolisib) concentrations in dog plasma has been developed and validated for the first time to support pre‐clinical drug development. Following protein precipitation with acetonitrile, the resulting samples were analyzed using reverse‐phase chromatography on a Metasil AQ column. The mass analysis was performed on a triple quadruple mass spectrometer coupled with an electrospray interface in positive ionization mode. The selected reaction monitoring transitions monitored were m/z 499.3 → 341.1 for GDC‐0980 and m/z 507.3 → 341.1 for IS. The method was validated over the calibration curve range 0.250–250 ng/mL with linear regression and 1/x² weighting. Relative standard deviation (RSD) ranged from 0.0 to 10.9% and accuracy ranged from 93.4 to 113.6% of nominal. Stable‐labeled internal standard GDC‐0980‐d₈ was used to minimize matrix effects. This assay was used for the measurement of GDC‐0980 dog plasma concentrations to determine toxicokinetic parameters after oral administration of GDC‐0980 (0.03, 0.1 and 0.3 mg/kg) to beagle dogs in a GLP toxicology study. Peak concentration ranged from 3.23 to 84.9 ng/mL. GDC‐0980 was rapidly absorbed with a mean time to peak concentration ranging from 1.3 to 2.4 h. Mean area under the concentration–time curve from 0 to 24 hours ranged from 54.4 to 542 ng h/mL. Copyright © 2015 John Wiley & Sons, Ltd.     

A rapid and sensitive determination of hypoxic radiosensitizer agent nimorazole in rat plasma by LC‐MS/MS and its application to a pharmacokinetic study

A highly sensitive, accurate and robust LC‐MS/MS method was developed and validated for determination of nimorazole (NMZ) in rat plasma using metronidazole (MNZ) as internal standard (IS). The analyte and IS were extracted from plasma by precipitating protein with acetonitrile and were chromatographed using an Agilent Poroshell 120, EC‐C₁₈ column. The mobile phase was composed of a mixture of acetonitrile and 0.1 % formic acid (85:15 v/v). The total run time was 1.5 min and injection volume was 5 μL. Multiple reaction monitoring mode using the transitions of m/z 227.1 → m/z 114.0 for MNZ and m/z 172.10 → m/z 128.1 for IS were monitored on a triple quadrupole mass spectrometer, operating in positive ion mode. The calibration curve was linear in the range of 0.25–200 ng/mL (r² > 0.9996) and the lower limit of quantification was 0.25 ng/mL in the rat plasma samples. Recoveries of NMZ ranged between 88.05 and 95.25%. The precision (intra‐day and inter‐day) and accuracy of the quality control samples were 1.25–8.20% and ?2.50–3.10, respectively. The analyte and IS were found to be stable during all sample storage and analysis procedures. The LC‐MS/MS method described here was validated and successfully applied to pharmacokinetic study in rats. Copyright © 2015 John Wiley & Sons, Ltd.     

A simple and sensitive LC‐MS/MS method for the determination of sotalol in rat plasma

A sensitive, rapid and robust HPLC method with tandem mass spectrometry (HPLC/MS/MS) detection has been developed and validated for the quantification of sotalol in rat plasma. Plasma samples were precipitated with acetonitrile before analysis. The chromatographic separation was performed on an Atlantis hydrophilic interaction liquid chromatography Silica column (50 × 2.1 mm, 3 µm) with a gradient mobile phase of 10 mm NH₄COOH (containing 0.2% of formic acid) as buffer A and acetonitrile as mobile phase B. Sotalol (m/z 273.2 → 255.1) and atenolol (the internal standard, IS, m/z 267.2 → 190.1) were monitored under positive ionization mode with 5500 QTRAP. Retention time of sotalol and the IS were 2.69 and 3.43 min, respectively. The linear range was 5–500 nm based on the analysis of 0.1 mL of plasma. The intrabatch precision ranged from 1.2 to 6.1%, and the inter‐batch precision was from 3.3 to 6.5%. The coefficient of variation of IS‐normalized matrix factor was 7.6%. Experiments for stability were performed and the analyte was sufficiently stable. A run time of 6 min for each injection made it possible to analyze a high throughput of plasma samples. The assay was successfully applied to the determination of sotalol in rat plasma after a micro‐dose oral administration. Copyright © 2014 John Wiley & Sons, Ltd.     

Development and application of a LC–MS/MS assay for the simultaneous quantification of edaravone and taurine in beagle plasma

An LC–MS/MS method was developed and validated for the simultaneous quantification of edaravone and taurine in beagle plasma. The plasma sample was deproteinized using acetonitrile containing formic acid. Chromatographic separations were achieved on an Agilent Zorbax SB‐Aq (100 × 2.1 mm, 3.5 μm) column, with a gradient of water (containing 0.03% formic acid) and methanol as the mobile phase at a flow rate of 0.3 mL/min. The analyte detection was carried out in multiple reaction monitoring mode and the optimized precursor‐to‐product transitions of m/z [M+H]⁺ 175.1 → 133.0 (edaravone), m/z [M+H]⁺ 189.1 → 147.0 (3‐methyl‐1‐p‐tolyl‐5‐pyrazolone, internal standard, IS), m/z [M–H]^? 124.1→80.0 (taurine), and m/z [M–H]^? 172.0 → 80.0 (sulfanilic acid, IS) were employed to quantify edaravone, taurine, and their corresponding ISs, respectively. The LOD and the lower LOQ were 0.01 and 0.05 μg/mL for edaravone and 0.66 and 2 μg/mL for taurine, respectively. The calibration curves of these two analytes demonstrated good linearity (r ＞ 0.99). All the validation data including the specificity, precision, recovery, and stability conformed to the acceptable requirements. This validated method has successfully been applied in the pharmacokinetic study of edaravone and taurine mixture in beagle dogs.     

An LC–MS/MS method for rapid and sensitive high‐throughput simultaneous determination of various protein kinase inhibitors in human plasma

A reliable, high‐throughput and sensitive LC–MS/MS procedure was developed and validated for the determination of five tyrosine kinase inhibitors in human plasma. Following their extraction from human plasma, samples were eluted on a RP Luna®‐PFP 100 Å column using a mobile phase system composed of acetonitrile and 0.01 m ammonium formate in water (pH ~4.1) with a ratio of (50:50, v /v) flowing at 0.3 mL min⁻¹. The mass spectrometer was operating with electrospray ionization in the positive ion multiple reaction monitoring mode. The proposed methodology resulted in linear calibration plots with correlation coefficients values of r ² = 0.9995–0.9999 from concentration ranges of 2.5–100 ng mL⁻¹ for imatinib, 5.0–100 ng mL⁻¹ for sorafenib, tofacitinib and afatinib, and 1.0–100 ng mL⁻¹ for cabozantinib. The procedure was validated in terms of its specificity, limit of detection (0.32–1.71 ng mL⁻¹), lower limit of quantification (0.97–5.07 ng mL⁻¹), intra‐ and inter assay accuracy (−3.83 to +2.40%) and precision (<3.37%), matrix effect and recovery and stability. Our results demonstrated that the proposed method is highly reliable for routine quantification of the investigated tyrosine kinase inhibitors in human plasma and can be efficiently applied in the rapid and sensitive analysis of their clinical samples.     

Quantitative determination of bilobetin in rat plasma by HPLC–MS/MS and its application to a pharmacokinetic study

Although bilobetin, a biflavone isolated from the leaves of Ginkgo biloba, represents a variety of pharmacological activities, to date there have been no validated determination methods for bilobetin in biological samples. Thus, we developed a liquid chromatographic method using a tandem mass spectrometry for the determination of bilobetin in rat plasma. After protein precipitation with acetonitrile including diclofenac (internal standard), the analytes were chromatographed on a reversed-phased column with a mobile phase of purified water and acetonitrile (3:7, v/v, including 0.1% formic acid). The ion transitions of the precursor to the product ion were principally deprotonated ions [M − H]⁻ at m/z 551.2 → 519.2 for bilobetin and 296.1 → 251.7 for the IS. The accuracy and precision of the assay were in accordance with US Food and Drug Administration regulations for the validation of bioanalytical methods. This analytical method was successfully applied to monitor plasma concentrations of bilobetin over time following intravenous administration in rats.     

A quantitative determination of fluorochloridone in rat plasma by UPLC‐MS/MS method: application to a pharmacokinetic study

A precise, high‐throughput and sensitive ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method has been developed for the determination of fluorochloridone (FLC) in rat plasma. The extraction of analytes from plasma samples was carried out by protein precipitation procedure using acetonitrile prior to UPLC‐MS/MS analysis. Verapamil was proved as a proper internal standard (IS) among many candidates. The chromatographic separation based on UPLC was well optimized. Multiple reaction monitoring in positive electrospray ionization was used with the optimized MS transitions at: m/z 312.0 → 292.0 for FLC and m/z 456.4 → 165.2 for IS. This method was well validated with good linear response (r² > 0.998) observed over the investigated range of 3–3000 ng/mL and with satisfactory stability. This method was also characterized with adequate intra‐ and inter‐day precision and accuracy (within 12%) in the quality control samples, and with high selectivity and less matrix effect observed. Total running time was only 1.5 min. This method has been successfully applied to a pilot FLC pharmacokinetic study after oral administration. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of rhynchophylline and hirsutine in rat plasma by UPLC‐MS/MS after oral administration of Uncaria rhynchophylla extract

An ultra‐performance liquid chromatography with tandem mass spectrometry (UPLC–MS/MS) method was developed and validated to concurrently determine rhynchophylline and hirsutine in rat plasma. The sample preparation of rat plasma was achieved by alkalization and liquid–liquid extraction. The mass transition of precursor ion → product ion pairs were monitored at m/z 385.2 → 160.0 for rhynchophylline, m/z 369.3 → 144.0 for hirsutine and m/z 414.0 → 220.0 for noscapine (internal standard). This method revealed linear relationships from 2.5 to 50 ng/mL (r² > 0.997) for rhynchophylline and from 2.5 to 50 ng/mL (r² > 0.998) for hirsutine. The limit of quantification values for rhynchophylline and hirsutine in rat plasma were both 2.5 ng/mL. Intra‐day and inter‐day precisions were within 10.6% and 12.5%, respectively, for rhynchophylline and hirsutine, and the accuracy (bias) was <10%. Liquid–liquid extraction of rat plasma samples resulted in insignificant matrix effect, and the extraction recoveries were >83.6% for rhynchophylline, 73.4% for hirsutine and 90.7% for the internal standard. This method was applied successfully to a pharmacokinetic study of rhynchophylline and hirsutine in rats after oral administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Development and validation of an LC‐MS/MS method for the determination of mesalazine in beagle dog plasma and its application to a pharmacokinetic study

A simple, specific and sensitive LC‐MS/MS method was developed and validated for the determination of mesalazine in beagle dog plasma. The plasma samples were prepared by protein precipitation, then the separation of the analyte was achieved on a Waters Spherisorb C₆ column (150 × 4.6 mm, 5 µm) with a mobile phase consisting of 0.2% formic acid in water–methanol (20:80, v/v). The flow rate was set at 1.0 mL/min with a split ratio of 3:2. Mass spectrometric detection was achieved by a triple‐quadrupole mass spectrometer equipped with an electrospray source interface in positive ionization mode. Quantitation was performed using selected reaction monitoring of precursor–product ion transitions at m/z 154 → m/z 108 for mesalazine and m/z 285 → m/z 193 for diazepam (internal standard). The linear calibration curve of mesalazine was obtained over the concentration range 50–30,000 ng/mL. The matrix effect of mesalazine was within ±9.8%. The intra‐ and inter‐day precisions were <7.9% and the accuracy (relative error) was within ±3.5%. The validated method was successfully applied to investigate the pharmacokinetics of mesalazine in healthy beagle dogs after rectal administration of mesalazine suppository. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantitation of glucosamine sulfate in plasma by HPLC-MS/MS after administration of powder for oral solution formulation

A rapid method for the quantification of glucosamine in human plasma using high‐performance liquid chromatography coupled to tandem mass spectrometry was developed and validated. The sample preparation includes a simple deproteinization step, using d ‐[1‐¹³C] glucosamine hydrochloride as an internal standard. Chromatographic separation was performed on an ACE Ciano column using isocratic elution with acetonitrile and aqueous 2 mm ammonium acetate containing 0.025% formic acid (80:20). Selected reaction monitoring was performed using the transitions m/z 180.1 → m/z 72.1 and m/z 181.0 → m/z 74.6 to quantify glucosamine and internal standard, respectively. The method was validated and proved to be linear, accurate and precise over the range 50–5000 ng/mL of glucosamine. Recovery rates higher than 90% were obtained for both glucosamine and internal standard. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after oral administration of a powder for oral solution formulation containing glucosamine sulfate. Copyright © 2011 John Wiley & Sons, Ltd.     

Simultaneous determination of 20(S)‐protopanaxadiol and its three metabolites in rat plasma by LC–MS/MS: application to their pharmacokinetic studies

The aim of this study was to develop an LC–MS/MS method for simultaneous determination of 20(S) protopanaxadiol (PPD) and its three metabolites, PPD‐glucuronide (M1), (20S,24S)‐epoxy‐dammarane‐3,12,25‐triol (M2) and (20S,24R)‐epoxydammarane‐3,12,25‐triol (M3), in rat plasma. Precipitation with acetonitrile was employed for sample preparation and chromatographic separations were achieved on a C₁₈ column. The sample was detected using triple quadrupole tandem mass spectrometer with selected reaction monitoring mode. The monitored precursor‐to‐product ion transitions were m/z 459.4 → 375.3 for PPD, m/z 635.4 → 113.0 for M1, m/z 477.4 → 441.4 for M2 and M3 and m/z 475.4 → 391.3 for IS. The developed assay was validated according to the guidelines of the US Food and Drug Administration. The calibration curves showed good linearity over the tested concentration ranges (r > 0.9993), with the LLOQ being 1 ng/mL for all analytes. The intra‐ and inter‐day precisions (RSD) were < 9.51% while the accuracy (RE) ranged from −8.91 to 12.84%. The extraction recovery was >80% and no obvious matrix effect was detected. The analytes were stable in rat plasma with the RE ranging from −12.34 to 9.77%. The validated assay has been successfully applied to the pharmacokinetic study of PPD as well as its metabolites in rat plasma. According to the pharmacokinetic parameters, the in vivo exposures of M1, M2 and M3 were 11.91, 47.95 and 22.62% of that of PPD, respectively.     

Development and validation of an LC‐MS/MS method for the determination of bullatine A in rat plasma: application to a pharmacokinetic study

Bullatine A is a diterpenoid alkaloid of Xue‐Shang‐Yi‐Zhi‐Hao (Aconitum brachypodum), which is widely used in traditional Chinese medicine for the treatment of rheumatism and pain. The plasma levels of bullatine A were measured by a rapid and sensitive LC‐MS/MS method. Samples were prepared using acetonitrile precipitation and the separation of bullatine A was achieved on a Capcell Pak MG‐C₁₈ column by isocratic elution using acetonitrile (phase A) and 0.1% formic acid (phase B, pH 4.0; A:B, 30:70, v/v) as the mobile phase at a flow rate of 0.5 mL/min. Detection was performed on a triple‐quadrupole tandem mass spectrometer by multiple‐reaction monitoring of the transitions at m/z 344.2 → 105.2 for bullatine A and m/z 256.2 → 167.1 for the internal standard. The linearity was found to be within the concentration range of 1.32–440 ng/mL with a lower limit of quantification of 1.32 ng/mL. Only 1.3 min was needed for an each analytical run. This method was successfully applied in the determination of the active component bullatine A in rat plasma after intramuscular administration of A. brachypodum injection. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous quantification of hyperin,reynoutrin and guaijaverin in mice plasma by LC‐MS/MS: application to a pharmacokinetic study

A specific and sensitive LC‐MS/MS assay was developed to simultaneously quantify three structurally similar flavonoid glycosides – hyperin, reynoutrin and guaijaverin – in mouse plasma. Biosamples were prepared by solid‐phase extraction. Isocratic chromatographic separation was performed on an AichromBond‐AQ C₁₈ column (250 × 2.1 mm, 5 μm) with methanol–acetonitrile–water–formic acid (20:25:55:0.1) as the mobile phase. Detection of hyperin, reynoutrin, guaijaverin and internal standard [luteolin‐7‐O‐β‐d ‐apiofuranosyl‐(1 → 6)‐β‐d ‐glucopyranoside] was achieved by ESI‐MS/MS in the negative ion mode using m/z 463 → m/z 300, m/z 433 → m/z 300, m/z 433 → m/z 300 and m/z 579 → m/z 285 transitions, respectively. Linear concentration ranges of calibration curves were 4.0–800.0 ng/mL for hyperin and reynoutrin and 8.0–1600.0 ng/mL for guaijaverin when 100 μL of plasma was analyzed. We used this validated method to study the pharmacokinetics of hyperin, reynoutrin and guaijaverin in mice following oral and intravenous administration. All three quercetin‐3‐O‐glycosides showed poor oral absorption in mice, and the absolute bioavailability of hyperin after oral administration of 100 mg/kg was 1.2%. Pretreatment with verapamil increased the peak concentration and area under the concentration–time curve of hyperin, which were significantly higher than the control values. The half‐life of hyperin with verapamil was significantly prolonged compared with that of the control. Copyright © 2016 John Wiley & Sons, Ltd.     

Simultaneous determination and pharmacokinetic study of giraldoid a,giraldoid B in rat plasma after oral administration of Daphne giraldii Nitsche extracts by LC–MS/MS

A simple sensitive LC–MS/MS method has been developed for the simultaneous determination of giraldoid A and giraldoid B in rat plasma. The method was applied to pharmacokinetics studies of the two compounds from Daphne giraldii Nitsche. Chromatographic separation was accomplished on an Acquity UPLC™ BEH C₁₈ column (100 × 2.1 mm, 1.7 mm) by gradient elution with a flow rate of 0.2 mL min⁻¹_. The method was linear over the concentration range of 1.0–1000 ng mL⁻¹, and the lower limits of quantification were 1.04 ± 0.10 and 1.04 ± 0.09 ng mL⁻¹, respectively. The intra‐ and inter‐day precisions (RSD) were <10.14 and 9.96%. The extraction recovery of the analytes was acceptable. Stability studies demonstrated that the two compounds were stable in the preparation and analytical process. The maximum plasma concentration was 687.78 ± 243.62 ng mL⁻¹ for giraldoid A and 952.38 ± 131.99 ng mL⁻¹ for giraldoid B. The time to reach the maximum plasma concentration was 0.50 ± 0.37 h for giraldoid A and 0.50 ± 0.66 h for giraldoid B. The validated method was successfully applied to investigate the concentration–time profiles of giraldoid A and giraldoid B.     

Relative tissue distribution and excretion studies of gastrodin and parishin from powder and extract of Gastrodiae Rhizoma in rat by UHPLC‐ESI‐MS/MS

New research has indicated that Gastrodiae Rhizome (GR) has potential anti‐diabetic and anti‐asthmatic effects in mouse models. On the basis of our previous study of the relative bioavailability of gastrodin (GAS) and parishin (PA) from extract and powder of GR, we performed further research on the tissue distribution and excretion of the two analytes. A reliable bioanalytical method for the quantification of GAS and PA in rat tissues and excretion is required. Chromatographic separation was carried out on a gradient mobile phase of acetonitrile–water with 0.1% formic acid. Calibration curves (1/x ² weighted) offered satisfactory linearity (r ² > 0.9835) within 100–3000 ng mL⁻¹ for GAS and (r ² > 0.9862) within 10–1000 ng mL⁻¹ for PA. The relative standard deviations of the intra‐day and inter‐day precision were all <14.98%, whilst the relative errors of the intra‐day and inter‐day accuracy were all within ±14.71%. The matrix effect and recovery values were satisfactory in all of the biological matrices examination. The data of relative differences in tissue distribution and excretion of GAS and PA from powder and extract of GR indicated that higher bioavailabilities for GAS and PA were obtained when a dosage of 4 g kg⁻¹ GR powder was used.     

Development and validation of UHPLC‐MS/MS assay for rapid determination of a carvone Schiff base of isoniazid (CSB‐INH) in rat plasma: application to pharmacokinetic study

In this study, a fast UHPLC‐MS/MS method was developed and validated for the determination of a novel potent carvone Schiff base of isoniazid (CSB‐INH) in rat plasma using carbamazepine as an internal standard (IS). After a single‐step protein precipitation by acetonitrile, CSB‐INH and IS were separated on an Acquity BEH^TM C₁₈ column (50 × 2.1 mm, 1.7 µm) under an isocratic mobile phase, consisting of acetonitrile: 10 mM ammonium acetate (95:5, v/v), at a flow rate of 0.3 mL/min. Quantification was performed on a triple quadrupole tandem mass spectrometer in multiple reactions monitoring mode by using positive electrospray ionization source. The precursor to product ion transitions were set at m/z 270.08 → 79.93 for CSB‐INH and m/z 237.00 → 178.97 for IS. The proposed method was validated in compliance with US Food and Drug Administration and European Medicines Agency guidelines for bioanalytical method validation. The method was found to be linear in the range of 0.35–2500 ng/mL (r² ≥ 0.997) with a lower limit of quantification of 0.35 ng/mL. The intra‐ and inter‐day precision values were ≤12.0% whereas accuracy values ranged from 92.3 to 108.7%. In addition, other validation results were within the acceptance criteria and the method was successfully applied in a pharmacokinetic study of CSB‐INH in rats. Copyright © 2014 John Wiley & Sons, Ltd.