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Enasidenib, an oral product for treating Acute Myeloid Leukemia, has been approved by FDA in Aug, 2017. In this study, we set up an ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method for measuring Enasidenib and imatinib (internal standard, IS), simultaneously. Enasidenib and imatinib were separated on an ACQUITY UPLC BEH C 18 Column (2.1 mm × 50 mm, 1.7 μm, 132 Å). Mass detection was carried out by electrospray ionization in the position mode, and the multiple reaction monitoring transitions were m/z  474.23 → 456.17 and m/z  494.30 → 394.20 for Enasidenib and imatinib, respectively. Linearity (2 − 500 ng·mL −1 , R 2  > 0.999), precision and accuracy (RE < ± 15%), extraction recovery (≥ 96.69%), matrix effect (≥ 96.47%) and stability (RE < ± 10%) were validated which demonstrated the robustness of our method. This rapid, efficient and reliable UPLC-MS/MS method shows specificity and repeatability of Enasidenib in rat plasma and can be used in further pharmacokinetic studies. [ABSTRACT FROM AUTHOR]

Polymyxin B has resurfaced as a last-line treatment for multi-drug resistant Gram-negative bacteria. Accurate characterization and quantification of polymyxin B components is necessary to optimize this therapy. We developed and validated a robust, straightforward LC–MS/MS method to quantify polymyxin B1 and B2, the primary polymyxin B components, in various matrices (cation-adjusted Mueller-Hinton broth (CAMHB), human and rat plasma). Of sample preparation approaches investigated, two protein precipitation/extraction methods were developed as part of an analytical strategy based upon reverse-phase LC–MS/MS using electrospray ionization in positive multiple-reaction monitoring mode. Both methods were validated over therapeutically and experimentally relevant concentration ranges (CAMHB: 0.1–8.0 μg/mL, rat and human plasma: 0.05–4.0 μg/mL). Quality control samples spanning a relevant concentration range were employed to assess intra- and inter-day accuracy (relative error (%RSD)) and precision (coefficient of variation (CV%)). For polymyxin B1 and B2 in CAMHB, inter-day standard deviations were 1.18–4.59% and 0.777–1.23%, respectively, and accuracies were 94.2–99.3% and 94.4–99.1%. For rat plasma, inter-day standard deviations were 1.53%–5.64% and 4.07%–8.26%. Accuracies were 100.6–108.9% and 96.1–108.1%. For human plasma, inter-day standard deviations were 2.77–7.32% and 1.55–7.29%. Accuracies were 89.6–96.4% and 92.9–102.0%. Extraction recoveries for all matrices were >93.5%. Adsorption, storage, and long-term stability were assessed and were acceptable. Accuracy, precision, and cost-efficiency make this an ideal approach for quantifying polymyxin B in in vitro and in vivo samples including those from rat and human subjects. [ABSTRACT FROM AUTHOR]

Acotiamide is a new prokinetic drug that is used to treat functional dyspepsia (FD). A sensitive and specific LC-MS-MS method has been developed and validated for the analysis of acotiamide in rat plasma. The assay involved a simple protein precipitation (PPT) step with methanol-acetonitrile (50:50, v/v) and a gradient elution using a mobile phase consisting of water containing 0.1% formic acid and methanol containing 0.1% formic acid. The analytes were chromatographed on a reversephase Agilent Zorbax XDB C18 column (2.1 mm× 50 mm, 3.5 μm) with a flowrate of 0.50 mL/min. The analytes were monitored by tandem-mass spectrometry with positive electrospray ionization. The precursor-product transitions (m/z) in the positive ion mode were 451.4→271.3 and 386.2→122.2 for acotiamide and buspirone (internal standard, IS), respectively. The assay was shown to be linear over the range of 0.10-200 ng/mL, with a lower limit of quantification of 0.10 ng/mL. The method was shown to be reproducible and reliable with the inter- and intra-batch accuracy and precision were within ±15%. The assay has been successfully used for pharmacokinetic evaluation of acotiamide after intravenous and oral administration of 10 mg/kg acotiamide in rats. The oral absolute bioavailability (F) of acotiamide in rats was estimated to be 38.4 ± 13.5% with an elimination half-life (t1/2) value of 9.11 ± 0.40 h. [ABSTRACT FROM AUTHOR]

In this study, a sensitive and rapid ultra performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method was developed to determine mangiferin and neomangiferin in rat plasma simultaneously. Chromatographic separation was carried out on an Acquity UPLC BEH C18 column and mass spectrometric analysis was performed using a Xevo TQD triple quadruple mass spectrometer coupled with an electrospray ionization (ESI) source. The MRM transitions of m / z 423.2 → 303.1 and m / z 585.0 → 273.1 were used to quantify for mangiferin and neomangiferin, respectively. The linearity of this method was found to be within the concentration range of 5–2000 ng/mL for mangiferin, and 2–1000 ng/mL for neomangiferin in rat plasma, respectively. Only 3.0 min was needed for an analytical run. This assay was used to support a preclinical study to investigate the pharmacokinetics of mangiferin and neomangiferin in rats. [ABSTRACT FROM AUTHOR]

In vivo rat kidney tissue metabolites of an anticancer drug, cisplatin (cis-diamminedichloroplatinum [II]) (CP) which is used for the treatment of testicular, ovarian, bladder, cervical, esophageal, small cell lung, head and neck cancers, have been identified and characterized by using liquid chromatography positive ion electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with on line hydrogen/deuterium exchange (HDX) experiments. To identify in vivo metabolites, kidney tissues were collected after intravenous administration of CP to adult male Sprague-Dawley rats (n = 3 per group). The tissue samples were homogenized and extracted using newly optimized metabolite extraction procedure which involves liquid extraction with phosphate buffer containing ethyl acetate and protein precipitation with mixed solvents of methanol-water-chloroform followed by solid-phase clean-up procedure on Oasis HLB 3cc cartridges and then subjected to LC/ESI-HRMS analysis. A total of thirty one unknown in vivo metabolites have been identified and the structures of metabolites were elucidated using LC-MS/MS experiments combined with accurate mass measurements. Online HDX experiments have been used to further support the structural characterization of metabolites. The results showed that CP undergoes a series of ligand exchange biotransformation reactions with water and other nucleophiles like thio groups of methionine, cysteine, acetylcysteine, glutathione and thioether. This is the first research approach focused on the structure elucidation of biotransformation products of CP in rats, and the identification of metabolites provides essential information for further pharmacological and clinical studies of CP, and may also be useful to develop various effective new anticancer agents. [ABSTRACT FROM AUTHOR]

An ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method was developed to determine liensinine in rat plasma using carbamazepine as the internal standard (IS). Sample preparation was accomplished through a protein precipitation procedure with acetonitrile to 0.1 ml plasma sample. The analyte and IS were separated on an Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) with the mobile phase of acetonitrile and 0.1% formic acid in water with gradient elution at a flow rate of 0.40 ml/min. The injection volume was 6 μl. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) by multiple reactions monitoring (MRM) of the transitions at m / z 611.6 → 206.2 for liensinine and m / z 237.1 → 194.2 for IS. The linearity of this method was found to be within the concentration range of 10–1000 ng/ml with a lower limit of quantification of 10 ng/ml. Only 3.0 min was needed for an analytical run. The matrix effect was 93.8–107.4% for liensinine. The intra- and inter-day precision (RSD %) were less than 9.9% and accuracy (RE %) was within ±10.5%. The recovery ranged from 76.2 to 86.8%. Liensinine was sufficiently stable under all relevant analytical conditions. The method was also successfully applied to the pharmacokinetic study of liensinine in rats. The pharmacokinetic parameters were demonstrated as followed: t 1/2 was 8.2 ± 3.3 h, C max was 668.4 ± 156.9 ng/ml, and AUC 0→∞ was 1802.9 ± 466.4 ng/ml h. [ABSTRACT FROM AUTHOR]

CAT ((+)-(13aS)-deoxytylophorinine) is a novel anticancer drug belonging to phenanthroindolizidine alkaloids. A sensitive and reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for simultaneous quantification of CAT and its pharmacologically active 3-O-desmethyl metabolite (S-4) was developed and validated in rat plasma using rotundine as the internal standard (IS). CAT, S-4 and IS were extracted by acetonitrile protein precipitation and separated on an Eclipse XDB-C18 column (1.8 μm, 4.6 mm × 50 mm) with acetonitrile–water (27:73, v/v) mobile phase containing 0.1% formic acid at a 0.4 mL/min flow rate. Positive ion electrospray ionization in multiple reaction monitoring mode was employed to measure CAT, S-4 and IS by monitoring the transitions m/z 364.2 → 70.1 for CAT, 350.1 → 70.1 for S-4 and 356.2 → 192.2 for IS. Good linear correlation ( r 2 > 0.991) was achieved for CAT and S-4 over the range of 0.214–128.16 and 0.044–11.00 ng/mL, respectively. The lower limit of quantification was 0.214 ng/mL for CAT and 0.044 ng/mL for S-4, using 50 μL rat plasma samples. The intra- and inter-day precisions were not exceed 15% and the accuracy ranged between 94.80% and 108.22%. The average extraction recoveries of both analytes were greater than 94.62%. The method was successfully applied to the pharmacokinetic study of CAT and S-4 in rats after oral administration. [ABSTRACT FROM AUTHOR]

A rapid, sensitive and selective high-performance liquid chromatography-tandem mass spectrometric method (HPLC-MS) was developed and validated to determine the 14-(3-methylbenzyl)matrine (3MBM) and 14-(4-methylbenzyl)matrine (4MBM) levels in rat plasma in the present study. The analytes were separated using a C18 column (1.9 μm, 2.1 mm × 100 mm) equipped with a Security Guard C18 column (5 μm, 2.1 mm × 10 mm), followed by detection via triple-quadrupole mass spectrometry using an electrospray ionization (ESI) source. Sample pretreatment involved one-step protein precipitation with isopropanol:ethyl acetate (v/v, 25:75), and pseudoephedrine hydrochloride was used as an internal standard. The method was linear in the concentration range of 5–2000 ng/ml for both compounds. The intra-day and inter-day relative standard deviations (RSDs) were less than 15%, and all relative errors (REs) were within 15%. The proposed method enables the unambiguous identification and quantification of these two compounds in vivo. This study is the first to determine the 3MBM and 4MBM levels in rat plasma after oral administration of these compounds. These results provide a meaningful basis for evaluating the clinical applications of these medicines. [ABSTRACT FROM AUTHOR]

A simple, rapid and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of six components including apigenin, quercetin, apigenin-7- O -β- d -glucoside, quercetin-3- O -β- d -glucoside, 3′-methoxyluteolin-7- O -β- d -glucoside, and tricin-7- O -β- d -glucopyranoside in rat plasma using formononetin as the internal standard (IS). The plasma samples were pretreated by a one-step liquid–liquid extraction with dichloromethane. The chromatographic separation was carried out on a ZORBAX SB-Aq column with a gradient mobile phase consisting of acetonitrile and 2 mM aqueous ammonium acetate. All analytes and IS were quantitated through electrospray ionization in negative ion multiple reaction monitoring mode. The mass transitions were as follows: m / z 269.1 → 117.2 for apigenin, m / z 301.2 → 151.2 for quercetin, m / z 431.3 → 311.2 for apigenin-7- O -β- d -glucoside, m / z 463.2 → 300.2 for quercetin-3- O -β- d -glucoside, m / z 461.3 → 283.1 for 3′-methoxyluteolin-7- O -β- d -glucoside, m / z 491.3 → 313.1 for tricin-7- O -β- d -glucopyranoside, and m / z 267.2 → 252.2 for IS, respectively. All calibration curves exhibited good linearity with correlation coefficient ( r ) > 0.995. The intra-day and inter-day precisions (RSD) at three QC levels were both less than 14.0% and the accuracies ranged from 89.8% to 113.8%. The extraction recoveries of six compounds ranged from 82.3% to 92.5%. The validated method was successfully applied to pharmacokinetic study of the six components in male rat plasma after oral administration of Paulownia tomentosa flower extract. [ABSTRACT FROM AUTHOR]

A highly selective and sensitive method for simultaneous quantitation of osthole, bergapten and isopimpinellin in rat plasma and tissues was developed by liquid chromatography–tandem quadrupole mass spectrometry (LC–MS/MS). After liquid–liquid extraction of samples with methyl tert-butyl ether, the analytes and dextrorphan (internal standard, IS) were separated by a Hypersil GOLD AQ C18 column with gradient elution of acetonitrile and water containing 0.5‰ formic acid. Three determinands were detected using an electrospray ionization (ESI) tandem mass spectrometry in the multiple reaction monitoring (MRM) modes with positive electrospray ionization. Calibration curves were recovered over the concentration ranges of 1–200 ng/ml, 1–500 ng/ml, 0.25–200 ng/ml for osthole, bergapten and isopimpinellin in plasma; 1–100 ng/ml, 1–500 ng/ml, 0.5–100 ng/ml for osthole, bergapten and isopimpinellin in tissues, respectively. The intra-day precision (R.S.D.) was within 13.90% and the intra-day accuracy (R.E.) was within −6.27 to 6.84% in all biological matrixes. The inter-day precision (R.S.D.) was less than 13.66% and the inter-day accuracy (R.E.) was within −10.64 to 13.04%. Then the method was successfully applied to investigate plasma pharmacokinetic study and tissue distribution of osthole, bergapten and isopimpinellin in rats after oral administration of Fructus Cnidii extraction, especially for testis/uterus tissue distribution. The results demonstrated that osthole, bergapten and isopimpinellin were absorbed and eliminated rapidly with wide distributions in rats. Distribution data of these three bioactive components in testis/uterus tissues could offer useful information for the further preclinical and clinical studies of Fructus Cnidii in the treatment of genital system disease. [ABSTRACT FROM AUTHOR]

A rapid, sensitive and selective liquid chromatography/tandem mass spectrometry method (LC-MS/MS) was developed and validated for determination of dehydrocorydaline (DHC) in rat plasma using nitidine chloride as an internal standard. The analytes were solid-phase extracted and eluted on a C18 chromatography column using a mobile phase of acetonitrile and water (containing 0.8% formic acid and 10 mM ammonium acetate) (28:72, v/v). Detection was performed using positive ion electrospray ionization in multiple reaction monitoring modes. The assay was linear over the concentration range 0.625-250 ng/mL with a quantification limit of 0.625 ng/mL. The precision was <13.7%, the accuracy >93.1%, and extraction recovery ranged from 92.1% to 107%. The validated method was successfully applied to the pharmacokinetics and excretion study of DHC in rat plasma after oral administration of pure DHC and an effective fraction of Corydalis yanhusuo (EFY). The pharmacokinetic parameters showed that DHC from EFY was absorbed more rapidly and eliminated more slowly than pure DHC. The result suggests that the differences might be due to the presence of P-glycoprotein (P-gp) inhibitors and that other alkaloids co-existing in the EFY may compete with DHC for transportation by P-gp, metabolization by P450, and binding to plasma proteins. [ABSTRACT FROM AUTHOR]

Fenofibrate (FF) lowers plasma triglycerides via PPARα activation. Here, we analyzed lipidomic changes upon FF treatment of fructose fed rats. Three groups with 6 animals each were defined as control, fructose-fed and fructose-fed/FF treated. Male Wistar Unilever Rats were subjected to 10% fructose-feeding for 20 days. On day 14, fenofibrate treatment (100 mg/kg p.o.) was initiated and maintained for 7 days. Lipid species in serum were analyzed using mass spectrometry (ESI-MS/MS; LC-FT-MS, GC-MS) on days 0, 14 and 20 in all three groups. In addition, lipid levels in liver and intestine were determined. Short-chain TAGs increased in serum and liver upon fructose-feeding, while almost all TAG-species decreased under FF treatment. Long-chain unsaturated DAG-levels (36:1, 36:2, 36:4, 38:3, 38:4, 38:5) increased upon FF treatment in rat liver and decreased in rat serum. FAs, especially short-chain FAs (12:0, 14:0, 16:0) increased during fructose-challenge. VLDL secretion increased upon fructose-feeding and together with FA-levels decreased to control levels during FF treatment. Fructose challenge of de novo fatty acid synthesis through fatty acid synthase (FAS) may enhance the release of FAs ≤16:0 chain length, a process reversed by FF-mediated PPARα-activation. [ABSTRACT FROM AUTHOR]

A liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed, using testosterone-d3 as a surrogate analyte, for the simultaneous quantification of goserelin and testosterone in rat plasma. According to this method, the pharmacokinetic and pharmacodynamic data were obtained from a single plasma sample aliquot. The method involved the addition of alarelin as an internal standard (IS) for goserelin and testosterone-13C3 for testosterone or testosterone-d3. The conditions for the separation of these two compounds were achieved on a ZORBAX Eclipse Plus C18 column (Agilent, 2.1×50mm, 1.8µm, Stockport, UK) in a single chromatographic run at a flow rate of 400µL/min. In order to minimize interferences of complex matrix, the extraction of plasma consisted of a protein precipitation step using methanol, followed by purification using an Oasis® HLB solid-phase extraction column. The method was validated in the concentration range of 0.01-30.0ng/mL for goserelin and 0.05-30.0ng/mL for testosterone-d3, respectively. The within- and between-run precisions were 1.7-9.2% and 2.1-6.9%, respectively. The within- and between-run accuracies were -1.8 to 5.3% and -4.9 to 4.0%, respectively. This accurate and highly specific assay provides a useful method to evaluate the pharmacokinetics and pharmacodynamics of goserelin in rats. [ABSTRACT FROM AUTHOR]

A rapid, sensitive and reliable liquid chromatography–tandem mass spectrometry method was developed and validated for the determination of betulonic acid in rat plasma. The plasma samples were prepared by protein precipitation. Chromatographic separation was achieved on an Agela MG-C18 analytical column (50 × 2.1 mm, 5 µm) using methanol–water–formic acid (80:20:0.1, v/v/v) as the mobile phase with a constant flow rate of 0.6 mL/min. Mass detection was conducted by electrospray ionization in positive ion multiple reaction monitoring mode. The calibration curves were linear over a concentration range of 3.00–3,000 ng/mL for the analyte. The intra-day and inter-day accuracy and precision were within the acceptable limits of ±15% at all concentrations. The method was successfully applied for the estimation of betulonic acid in rat plasma from a preclinical pharmacokinetics study. [ABSTRACT FROM AUTHOR]

Highlights: [•] In vivo metabolism of 20(S)-protopanaxatriol (PPT) was first investigated by UPLC–Q/TOF-MS. [•] Total of 22 metabolites were detected and identified. [•] Oxidation, glucuronidation and cysteine-conjugation were the main metabolic pathways. [ABSTRACT FROM AUTHOR]

A new ultra-performance liquid chromatography–electrospray ionization mass spectrometry (UPLC–MS/ESI) method for simultaneous determination of venlafaxine (VEN) and its metabolite O-desmethylvenlafaxine (ODV) in rat plasma has been developed and validated using Venlafaxine d6 as the internal standard. The compounds and internal standard were extracted from plasma by solid phase extraction. The UPLC separation of the analytes was performed on ACQUITY UPLC® BEH Shield RP18 (1.7µm, 100mm×2.1mm) column, using isocratic elution with mobile phase constituted of water (containing 2mM ammonium acetate): acetonitrile (20:80, v/v) at a flow rate of 0.3mL/min. All of the analytes were eluted within 1.5min. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer, operating in multiple reaction monitoring (MRM) and positive ion mode. The precursor to product ion transitions monitored for VEN, ODV and Venlafaxine d6 were m/z 278.3→121.08, 264.2→107.1 and 284.4→121.0, respectively. The developed and validated method was used for the pharmacokinetic study of VEN in rats. [ABSTRACT FROM AUTHOR]

Highlights: [•] Neutral pentacyclic triterpenes such as betulin cannot be easily ionized by ESI. [•] Betulin reacted with PTSI and generated an ionizable and fragmentable derivative. [•] A LC–ESI/MS/MS method for the quantification of betulin in rat plasma was developed. [•] The LC–MS/MS method was applied to the pharmacokinetic study of betulin in rats. [Copyright &y& Elsevier]

A sensitive and accurate ultra-performance liquid chromatography coupled with triple quadrupole mass (UPLC-MS/MS) method was developed for the determination of quercetin-3-O-β-D-glucopyranoside-(4→1)-α-L-rhamnoside (QGR) in rat plasma using rutin as internal standard. Chromatographic separation was achieved on a Acquity BEH C18 column (100 mm × 2.1 mm, 1.7 μm) with a gradient elution of acetonitrile and 0.10% formic acid (v/v) at a flow rate of 0.4 mL/min. QGR and rutin were detected using electrospray negative ionization mass spectrometry in the multiple reaction monitoring (MRM) mode. The method demonstrated good linearity and did not show any endogenous interference with the QGR and rutin peaks. This method was successfully applied to a pharmacokinetic study of QGR in rats after intravenous (20 mg/kg) and oral (40 mg/kg) administration, and the results showed that the compound was poorly absorbed, with an absolute bioavailability of approximately 3.41%. [ABSTRACT FROM AUTHOR]

A sensitive and simple liquid chromatography/electrospray mass spectrometry (LC-ESI-MS) method for determination of diphenoxylate in rat plasma using one-step protein precipitation was developed and validated. After addition of estazolam as internal standard (IS), protein precipitation by acetonitrile was used as sample preparation. Chromatographically separation was achieved on an SB-C18 (2.1 mm × 50 mm, 3.5 µm) column with acetonitrile-0.1% formic acid as the mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; selected ion monitoring (SIM) mode was used to quantification using target fragment ionsm/z453.1 for diphenoxylate andm/z294.8 for the IS. Calibration plots were linear over the range of 5–1000 ng/mL for diphenoxylate in rat plasma. Lower limit of quantification (LLOQ) for diphenoxylate was 5 ng/mL. Mean recovery of diphenoxylate from plasma was in the range of 96.69–98.27%. RSD of intra-day and inter-day precision were both less than 9%. This method is simple and sensitive enough to be used in pharmacokinetic research for determination of diphenoxylate in rat plasma. [ABSTRACT FROM AUTHOR]

A highly selective and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of scicinib, a novel thiosemicarbazone analogue and anticancer agent in rat plasma. Protein precipitation with saturated EDTA solution and methanol was selected for sample preparation, and brodimoprim was employed as the internal standard (IS). The analytes were separated on a Symmetry C18column (200 × 4.6 mm i.d., 5 µm) by isocratic elution with a mobile phase consisting of methanol and 0.2 mM EDTA (75:25, v/v) at a flow rate of 0.4 mL/min. After electrospray ionization, the analyte and IS were recorded under selected reaction monitoring (SRM) mode. The chosen transition wasm/z313.0 → 267.9 for scicinib andm/z339.0 → 280.9 for IS, respectively. The validated linearity range is 5–5000 ng/mL, with the lower limit of quantitation of 5 ng/mL. The developed method was successfully applied to a pharmacokinetic study of scicinib in rats after a single intravenous administration of 5 mg/kg. [ABSTRACT FROM AUTHOR]

A rapid sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for determination of timosaponin AIII (TA-III) in rat plasma, using ginsenoside Re as an internal standard (IS). TA-III and the IS were detected in MRM mode with a negative ionization electrospray mass spectrometer. The calibration curves were linear over the concentration ranges from 11.14 to 1114 ng/mL and the lower limit of quantification (LLOQ) was 11.14 ng/mL. Intra-day and inter-day precisions (RSD) were within 10%, and accuracy ranged from 6.4% to 9.1%. The extraction recovery at three concentrations ranged from 92.3% to 95.5%. The validated method was successfully applied to monitor the concentrations of TA-III in rat plasma after intragastric administration. The best fit pharmacokinetic model to estimate the pharmacokinetic parameters was a single compartment model with weight of 1/x2 for oral administration groups of rats for TA-III. [ABSTRACT FROM AUTHOR]

Abstract: A selective and sensitive liquid chromatography–mass spectrometry (LC–MS) method was developed for the simultaneous determination of Euphorbia factor L1, Euphorbia factor L2 and Euphorbia factor L3 from Euphorbiae semen in rat plasma. Larotaxel was added to a 200μL plasma sample as the internal standard (IS). The plasma sample was extracted by 2mL ether and separated on an Elite C18 column (150mm×4.6mm, 5μm) with the mobile phase of methanol–water performing gradient elution within 11.0min. All the three analytes were detected in the selected ion monitoring (SIM) mode with positive electrospray ionization. The calibration curves were linear in the range of 2.0–200ng/mL and the lower limits of quantification (LLOQ) were 2.0ng/mL for all the three analytes. The intra-day and inter-day precisions were all within 8.6% and 14.6% for the three analytes, while the accuracy was less than 9.7% and 7.5%, respectively. The validated method was firstly and successfully applied to the pharmacokinetic study of Euphorbia factor L1, Euphorbia factor L2 and Euphorbia factor L3 from Euphorbiae semen after oral administration in rat plasma. [Copyright &y& Elsevier]

Abstract: A specific and reliable liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed for the simultaneous determination of tetrahydropalmatine (THP), tetrahydroberineper (THB), tetrahydrocoptisine (THC) and corydaline (CDL) in rat plasma using jatrorrhizine as internal standard. Plasma samples were pretreated by protein precipitation with acetonitrile. Chromatographic separation was performed on a Zorbax Eclipse Plus C18 column (3.0mm×100mm, 1.8μm) with gradient elution using acetonitrile–0.1% formic acid water as mobile phase at a flow rate of 0.3mL/min. The detection was carried out by a triple–quadrupole tandem mass spectrometer in multiple-reaction monitoring mode. The mass transition ion-pair was followed as m/z 356.2→192.1, m/z 324.1→176.0, m/z 340.1→176.0, and m/z 370.3→192.1 for THP, THC, THB and CDL. Linear calibration curves were obtained over the range of 0.2–2000ng/mL, and the method limits were 2.0ng/mL for THC, 0.2ng/mL for THB, 1.0ng/mL for THP, and 0.4ng/mL for CDL, respectively. The mean recovery of the analytes ranged from 85.51% to 93.99%. The intra- and inter-day precisions were in the range of 1.21–4.73% and the accuracies were between 92.23% and 98.23%. The validated method was successfully applied to a pharmacokinetic study of THP, THB, THC and CDL in rat plasma following oral administration of Jitai tablet. [Copyright &y& Elsevier]

Abstract: This work proposes a liquid chromatography–electrospray ionization ion trap mass spectrometry (LC–ESI-ITMS) method, for the quantification of sildenafil (SDF), tadalafil (TDF) and vardenafil (VDF) and their metabolites N-desmethylSDF, O-desethylSDF and N-desethylVDF, preceded by a sample preparation step based on protein and phospholipid elimination. A C8 column (150mm×4.6mm, 5μm) with ammonium formate (20mM) and acetonitrile as the mobile phase components have been used. This method has been validated, obtaining limits of quantification ranged from 1 to 2.5ng/mL and 2 to 5ng/g in serum and brain tissue respectively, while limits of detection ranged from 0.3 to 0.9ng/mL in serum and 0.6 to 1.9ng/g in brain tissue. Assay recoveries for low level QC samples were higher than 83% and the matrix effect ranged between 91% and 108% in serum and between 98% and 107% in brain tissue. The method has been applied to the quantification of these compounds in the serum and brain tissue of rats treated intraperitoneally with 10mg/kg of SDF, TDF or VDF. [Copyright &y& Elsevier]

Abstract: A new liquid chromatography–tandem mass spectrometry (LC–MS/MS) method operated in the negative electrospray ionization (ESI) switching mode has been developed and validated for the simultaneous determination of esculin and its metabolite esculetin in rat plasma. After addition of internal standards scopoletin, the plasma sample was pretreated by solid-phase extraction (SPE), and separated on a reversed phase C18 column with a mobile phase of 0.01% formic acid in water (solvent A) and methanol (solvent B) using isocratic elution (A:B=20:80, v/v). The detection of target compounds was done in multiple reaction monitoring (MRM) mode. The MRM detection was operated in the negative ESI mode using the transitions of m/z 339.1 ([M−H]−)→176.7 for esculetin, m/z 176.9 ([M−H]−)→133.0 and m/z 191.0 ([M−H]−)→175.9 for scopoletin. The standard curves, which ranged from 25 to 3200ng/mL for esculin with the lowest limit of quantification (LLOQ) of 0.25ng/mL and from 1.25 to 160ng/mL for esculetin with the LLOQ of 1.25ng/mL, were fitted to a 1/x weighted quadratic regression model. The method also afforded satisfactory results in terms of the sensitivity, specificity, precision (intra- and inter-day, RSD<8.73%), accuracy, recovery as well as the stability of the analyte under various conditions. The method was successfully applied to study the pharmacokinetics of esculin and its metabolite esculetin in rat plasma after oral administration of esculin at a dose of 100mg/kg. [Copyright &y& Elsevier]

A sensitive and selective liquid chromatography-mass spectrometry (LC-MS) method for determination of tolbutamide and its metabolite hydroxytolbutamide in rat plasma was developed and validated. The analytes and internal standard omeprazole were extracted from plasma by liquid-liquid extraction using ethyl acetate, and chromatographically separated on a Zorbax SB-C18 column (2.1 mm × 50 mm, 3.5 µm) using acetonitrile-0.1% formic acid as the mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode, and selected ion monitoring (SIM) mode used to quantify tolbutamide and its metabolite hydroxytolbutamide. The assay was linear over the range 10–20000 ng/mL for tolbutamide and 5–800 ng/mL for hydroxytolbutamide, with a lower limit of quantification (LLOQ) of 10 ng/mL for tolbutamide and 5 ng/mL for hydroxytolbutamide. Intra- and inter-day precision were less than 12% and the accuracy were in the range 88.8–109.7%. This developed method was successfully used for determination of tolbutamide and metabolite hydroxytolbutamide in rat plasma for pharmacokinetic study. [ABSTRACT FROM AUTHOR]

Abstract: Decitabine is chemically unstable at physiological temperature and pH. In addition, the bioanalysis of decitabine is easily interfered by endogenous 2-deoxycytidine. A simple, sensitive and specific LC–MS/MS method was developed for the analysis of decitabine in rat plasma. No exogenous stabilizers were used to prevent the degradation of decitabine in rat plasma. After deproteinized with acetonitrile at room temperature, rat plasma samples were analyzed on a Hypersil APS-2 NH2 column interfaced with a triple quadrupole tandem mass spectrometer in positive electrospray ionization mode. Decitabine was completely separated from 2-deoxycytidine using gradient elution of water (solvent A) and acetonitrile (solvent B) at a flow rate of 1mL/min. To quantify decitabine and daidzin (internal standard), respectively, multiple reaction monitoring (MRM) transitions of m/z 251.1→134.7 and m/z 417.3→255.3 was performed. The assay was linear over the concentration range of 5.0–2000ng/mL. The intra- and inter-day precision was within 12.0% in terms of relative standard deviation (RSD%) and the accuracy within 5.9% in terms of relative error. The LC–MS/MS method was fully validated for its sensitivity, selectivity, stability study, matrix effect and recovery. The data indicate that this LC–MS/MS method is a specific and effective method for the pharmacokinetic study of decitabine in rat plasma. Compared with the previously reported analytical methods, this method showed easy and economic sample preparation, good specificity and high sensitivity with less plasma (50μL). [Copyright &y& Elsevier]

Abstract: A novel, simple, and sensitive method for the determination of jujuboside A in rat plasma using liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) was developed. Following solid-phase extraction, measurement of jujuboside A was performed by negative ion electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The limit of detection was 1.25ng/mL, and the lower limit of quantification was 5ng/mL in rat plasma. Good linearity was obtained over the range of 6.25–500ng/mL, and the correlation coefficient was better than 0.998. The intra- and inter-day precisions ranged 4.4–7.5% and 2.9–10.7%, respectively. The accuracy derived from QC samples ranged 3.2–7.8% and 2.2–3.5%, respectively. The recovery ranged from 72.9 to 75.1% and the matrix effect from 96.7 to 105.3%. The analyte was stable under various conditions (at room temperature, during freeze–thaw, in the autosampler and under deep-freeze conditions). The developed method was successfully applied to the pharmacokinetic study in rats. [Copyright &y& Elsevier]

Abstract: A liquid chromatography–mass spectrometry method has been developed and validated for the quantification of bullatacin, a bistetrahydrofuran annonaceous acetogenin, in rat plasma. Squamostatin-A was selected as the internal standard. Analytes were extracted from rat plasma by liquid/liquid extraction using ethyl acetate with high efficiency. The chromatographical separation was performed on an Agilent Zorbax SB-C18 column (150mm×2.1mm, 5μm). The mobile phase consisted of methanol and deionized water (95:5, v/v) containing 0.01% (v/v) formic acid. The chromatographic run time was 7min per injection and flow rate was 0.2mL/min. The retention time was 3.22 and 5.23min for internal standard and bullatacin, respectively. The elutes were detected under positive electrospray ionization and the target analytes quantified by selected ion monitoring mode (645.9 m/z for bullatacin and 661.9 m/z for squamostatin-A). The method was sensitive with the limit of quantitation at 0.5ng/mL in 100μL of rat plasma. Good linearity (r 2 =0.9998) was obtained covering the concentration of 0.5–2000ng/mL. The intra- and inter-day assay precision ranged from 3.2 to 8.7% and 2.7 to 9.2%, respectively. In addition, the stability, extraction recovery and matrix effect involved in the method were also validated. This method was applied to measure the plasma bullatacin concentrations after a single tail vein intravenous administration of bullatacin in rats. [Copyright &y& Elsevier]

Abstract: A new liquid chromatography–electrospray ionization–mass/mass spectrometry (LC–ESI–MS/MS) assay method has been developed and validated for the quantification of nitidine chloride (NC), an anti-cancer bioactive substance of Zanthoxylum nitidum (Roxb.) DC. plants, in rat plasma using carbamazepine as an internal standard (I.S.). The NC and I.S. were extracted from rat plasma by acetonitrile protein procedure. Chromatographic separation was carried out with a C18 column (2.1mm×150mm, 3μm) with a security guard C18 column (4mm×20mm, 3μm). The mobile phase consisted of acetonitrile–10mM ammonium acetate buffer solution–formic acid (35:65:0.2, v/v/v) and delivered at the flow rate of 0.25mL/min. LC–ESI–MS/MS was performed on a triple-quadrupole mass spectrometry equipped with electrospray ionization (ESI) and positive multiple reaction monitoring (MRM). Target ions were monitored at [M]+ m/z 348.2 for NC and [M]+ m/z 237.2 for I.S. The method was linear over the concentration range of 5.0–1500.0ng/mL. The intra- and inter-day relative standard deviations of the assay were less than 5.0%. The lower limit of quantification was 5.0ng/mL. The developed method was successfully applied to the estimation of the pharmacokinetic parameters of NC by intravenous administration to rats. [Copyright &y& Elsevier]

Abstract: A sensitive, specific, and rapid liquid chromatography–mass spectrometry (LC–MS) method was developed and validated for analysis of lasiodonin, oridonin, ponicidin, and rabdoternin A in rat plasma using sulfamethoxazole as an internal standard (IS). The plasma samples were pretreated and extracted by liquid–liquid extraction. Chromatographic separation was performed on a C18 column with linear gradient elution using water and methanol, both of which were acidified with 0.1% aqueous formic acid, at a flow rate of 0.8ml/min. Detection was accomplished by scanning with multiple reaction monitoring (MRM) via an electrospray ionization (ESI) source. Higher sensitivity was achieved by setting three scanning periods in a novel detection mode. The optimized mass transition ion pairs (m/z) for quantitation were 365.3/347.3 for lasiodonin and oridonin, 361.2/343.2 for ponicidin, 363.2/283.1 for rabdoternin A, and 254.1/156.0 for IS. The total run time was 13.50min between injections. The specificity, linearity, accuracy, precision, recovery, matrix effect, and several stabilities were validated for all analytes in the rat plasma samples. In conclusion, the validation results demonstrate that this method is robust and specific. The proposed method was further applied to investigate the pharmacokinetics of all analytes after a single oral administration of Isodon rubescens extract to rats. [ABSTRACT FROM AUTHOR]