A rapid and sensitive LC-MS/MS assay to quantify yonkenafil in rat plasma with application to preclinical pharmacokinetics studies

A novel method for the quantitation of yonkenafil, a new synthetic phosphodiesterase V inhibitor, in rat plasma using high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed. The analyte and internal standard (diazepam) were extracted from plasma (100 microl) by liquid-liquid extraction and separated on a C18 column using 10mM ammonium acetate buffer: methanol (15:85, v/v) as mobile phase in a run time of 3.0 min. The detector was a Q-trap mass spectrometer with an ESI interface operating in the multiple reaction monitoring (MRM) mode. The assay was linear over the concentration range 1.0-1000 ng/ml with a limit of detection of 0.20 ng/ml. Intra- and inter-day precision (as relative standard deviation) were both within 8.45% with good accuracy. The method was successfully applied to a preclinical pharmacokinetic study of yonkenafil in rat after sublingual, oral and intravenous administration. The results demonstrate that the sublingual route gives a higher bioavailablity than the oral route and may represent a useful alternative route of yonkenafil administration.     

Determination of S-propargyl-cysteine in rat plasma by mixed-mode reversed-phase and cation-exchange HPLC-MS/MS method and its application to pharmacokinetic studies

A simple, fast and sensitive mixed-mode reversed-phase and cation-exchange HPLC-MS/MS method for the quantification of S-propargyl-cysteine (SPRC), a novel cardioprotective agent, has been developed and validated for preclinical studies. Chromatographic separation of SPRC and its internal standard (IS) was performed using a commercial analytical column which contained both C18 bonded silica particles and sulfonic acid cation-exchange particles. The optimized mobile phase was composed of acetonitrile/ammonium acetate buffer (10mM, pH 4): 30/70 (v/v). Quantification was conducted by multiple reaction monitoring (MRM) of the transitions of m/z 160.0 → 143.0 for SPRC and 178.1 → 160.9 for S-butyl-cysteine (IS). The assay utilized methanol to achieve a simple and fast deproteinization. The lower limit of quantification (LLOQ) was 0.6 μg/mL (diluted with 50-fold of methanol) using 20 μL rat plasma. The assay was linear over a range from 0.6 to 159 μg/mL, with intra- and inter-batch accuracy (as relative error) less than ± 5% and precision (as relative standard deviation) less than 10%. Using the validated assay, the pharmacokinetic properties of SPRC in rats were investigated. SPRC exhibits linear pharmacokinetics after oral or intravenous administration in rats. The bioavailability after oral administration at 25, 75, and 225 mg/kg was 96.6%, 97.0%, and 94.7%, respectively.     

A rapid and sensitive liquid chromatography–tandem mass spectrometric method for the determination of timosaponin B-II in blood plasma and a study of the pharmacokinetics of saponin in the rat

A rapid, sensitive and selective liquid chromatography–tandem mass spectrometric (LC–MS/MS) method was developed and validated for the determination of Timosaponin B-II (TB-II), a pharmacologically active constituent isolated from Anemarrhena asphodeloides. This method was used to examine the pharmacokinetics and bioavailability of TB-II in rats using ginsenoside Re as an internal standard. After simple protein precipitation of the plasma samples with acetonitrile, the analytes were separated on an ODS column (150 mm × 2.1 mm i.d., 5 μm) with the mobile phase of acetonitrile–water (35:65, v/v) containing 0.05% formic acid and detected by electrospray ionization mass spectrometry in the negative multiple reaction monitoring (MRM) mode with a chromatographic run time of 3.0 min. The calibration curves were linear over the range of 5–15,000 ng/ml and the lower limit of quantification (LLOQ) was 5 ng/ml in rat plasma. In this range, relative standard deviations (R.S.D.) were <7.4% for intra-day precision and <9.0% for inter-day precision. The accuracy was within the range of 97.7–107.3%. The method was successfully applied to assess the pharmacokinetics and oral bioavailability of TB-II after intravenous and oral administration in rats, with the oral bioavailability being only 1.1%.     

A method for confirming CJC‐1295 abuse in equine plasma samples by LC–MS/MS

CJC‐1295 is a peptide‐based drug that stimulates the production of growth hormone (GH) from the pituitary gland. It incorporates a functional maleimido group at the C‐terminus that allows it to covalently bind plasma proteins such as serum albumin. These CJC‐1295‐protein conjugates have a much greater half‐life compared to the unconjugated peptide and are capable of stimulating GH production for more than six days in humans after a single administration. Conjugated CJC‐1295 is difficult to detect in blood by mass spectrometry due to its low abundance, high molecular weight, and conjugation to a range of different protein substrates. Previously we described a screening procedure for the detection of CJC‐1295 in equine plasma using an immuno‐PCR assay. Here we demonstrate the confirmation of CJC‐1295 in equine plasma by LC?MS/MS after immuno‐affinity capture and tryptic digestion. Using this method, CJC‐1295 was identified down to concentrations as low as 180 pg/mL in 1 mL of equine plasma.     

An LC–MS/MS method for determination of bioactive components of liquorice and Semen Strychni in rat plasma: Application to a pharmacokinetics study

Semen Strychni is known for its treatment of rheumatic arthritis with a low therapeutic index. Liquorice contributes a lot in herb detoxification according to the traditional Chinese medicine theory. A simple, rapid, and sensitive liquid chromatography–mass spectrometric method (LC–MS) was developed and validated for simultaneous determination of main bioactive ingredients in liquorice and Semen Strychni in rat plasma. Using moclobemide and cyproterone acetate as the internal standards, the analytes were pretreated via protein precipitation with methanol. An Ultimate AQ‐C18 column (3.0 μm, 3.0 × 100 mm) was employed for chromatographic separation, combining with gradient elution. The mobile phase consisted of 0.07% formic acid and 0.12% ammonium acetate in aqueous phase (A) and acetonitrile in organic phase (B). The elution program was as follows: 0–0.5 min, 20% B; 0.5–1 min, 20–60% B; 1–7 min, 60–85% B; and 7–7.5 min, returned to 20% B, then continued to 12 min. Selected reaction monitoring was performed in both positive and negative ESI. Positive mode was adopted for detection of strychnine, brucine, and moclobemide, while negative mode was used for glycyrrhizic acid, glycyrrhetinic acid, liquiritigenin, isoliquiritigenin, liquiritin, and cyproterone acetate. The method was validated for specificity, linearity, matrix effect, recovery, precision, accuracy, and stability. The results show that this method is sensitive, accurate and robust for biological matrix analysis. Moreover, the proposed method was applied to a pharmacokinetic study in Sprague–Dawley rats for investigating the mechanism of which liquorice detoxifies Semen Strychni.     

Development and validation of an LC–MS/MS method for quantification of NC-8 in rat plasma and its application to pharmacokinetic studies

ent-16-Oxobeyeran-19-N-methylureido (NC-8) is a recently synthesized derivative of iso-steviol that showed anti-hepatitis B virus (HBV) activity by disturbing replication and gene expression of the HBV and by inhibiting the host toll-like receptor 2/nuclear factor-κB signaling pathway. To study its pharmacokinetics as a part of the drug development process, a highly sensitive, rapid, and reliable liquid chromatography tandem mass spectrometry (LC–MS/MS) method was developed and validated for determining NC-8 in rat plasma. After protein precipitation extraction, the chromatographic separation of the analyte and internal standard (IS; diclofenac sodium) was performed on a reverse-phase Luna C₁₈ column coupled with a Quattro Ultima triple quadruple mass spectrometer in the multiple-reaction monitoring mode using the transitions, m/z 347.31 → 75.09 for NC-8 and m/z 295.89 → 214.06 for the IS. The lower limit of quantitation was 0.5 ng/mL. The linear scope of the standard curve was between 0.5 and 500 ng/mL. Both the precision (coefficient of variation; %) and accuracy (relative error; %) were within acceptable criteria of <15%. Recoveries ranged from 104% to 113.4%, and the matrix effects (absolute) were nonsignificant (CV ≤ 6%). The validated method was successfully applied to investigate the pharmacokinetics of NC-8 in male Sprague–Dawley rats. The present methodology provides an analytical means to better understand the preliminary pharmacokinetics of NC-8 for investigations on further drug development.     

Quantification of CKD-501, lobeglitazone, in rat plasma using a liquid-chromatography/tandem mass spectrometry method and its applications to pharmacokinetic studies

CKD-501 (i.e., lobeglitazone), a potent agonist for both PPARα/γ, is a new drug that has potential clinical applications in the management of type-2 diabetes. The objective of this study was to develop a rapid and sensitive method for the determination of CKD-501 in rat plasma and to assess the applicability of the assay to pharmacokinetic studies. Rat plasma samples were processed using a fast flow protein precipitation (FF-PPT) method and then introduced onto an LC–MS/MS system for quantification. The analyte and rosiglitazone, an internal standard, were analyzed by multiple reactions monitoring (MRM) at m/z transitions of 482.0 → 258.0 for CKD-501 and 358.0 → 135.0 for the internal standard. The lower limit of quantification (LLOQ) was determined at 50 ng/mL, with an acceptable linearity in the range from 50 to 10,000 ng/mL (R > 0.999). Validation parameters such as accuracy, precision, dilution, recovery, matrix effect and stability were found to be within the acceptance criteria of the assay validation guidelines, indicating that the assay is applicable to estimating the concentration in the range studied. The concentration of CKD-501 was readily quantifiable in plasma samples up to 24 h post-dose in rats that had received an oral dose of 1 mg/kg. These observations suggest, therefore, that the validated assay can be used in pharmacokinetic studies of CKD-501 in small animals such as the rat.     

Rapid and sensitive HPLC-MS/MS method for quantitative determination of isochlorogenic acid B in rat plasma and its application in pharmacokinetic study

Asensitive LC-ESI-MS/MS method for determination of isochlorogenic acid B in rat plasma was developed and validated in the present study. Plasma samples were prepared by a simple protein precipitation with methanol containing resveratrol as internal standard (IS). The chromatographic separation was performed on a Zorbax SB-C₁₈ column (3.5 μm, 2.1 mm×100 mm, Agilent, USA) at a flow rate of 0.2 mL/min using methanol/water containing 0.1% formic acid (v/v) as mobile phase. The detectionwas performed on a triple quadrupole tandem mass spectrometer equipped with Electronic Spray Ion by selected reaction monitoring (SRM) of the transitions at m/z 515.3→352.9 for isochlorogenic acid B and m/z 227.1→143.1 for IS, respectively. The calibration curve of the method was linear over the range of 5–2500 ng/mL (r² = 0.9982). The intra- and inter-day precisions (R.S.D.%) were less than 12.46%, and the accuracy (R.E.%) was within ±5.80%. Isochlorogenic acid B was sufficiently stable under all relevant analytical conditions. The validated method was successfully applied to the plasma pharmacokinetic studies of isochlorogenic acid B in rats. It was found that isochlorogenic acid B had non-linear pharmacokinetic characteristics in rats within the dosage ranges from 5 to 20 mg/kg.     

Development,validation, and application of an LC–MS/MS method for mitragynine and 7‐hydroxymitragynine analysis in hair

The entire scalp hair of a self‐declared Kratom consumer of 3 grams per day was acquired during an ethical committee approved study. As no values of the concentration in hair of the two Kratom alkaloids mitragynine or 7‐hydroxymitragynine were found in the literature, an already established method for the analysis of benzodiazepines/z‐substances was extended for the detection of mitragynine and 7‐hydroxymitragynine with LC–MS/MS, and successfully validated. The limits of detection and quantification for mitragynine were 2 pg/mg and 4 pg/mg, respectively. Those of 7‐hydroxymitragynine were 20 pg/mg and 30 pg/mg, respectively. The method was applied to the entire scalp hair, divided in 91 regions, of the study participant. A narrow mitragynine concentration distribution with values between 1054 pg/mg and 2244 ng/mg (mean 1517 ng/mg) and no clear scalp region associated distribution pattern was obtained. 7‐Hydroxymitragynine was not detected in any hair sample. After validation, the method was established as routine and subsequently 300 samples (mainly abstinence controls for drugs of abuse) were analyzed, allowing the investigation of the prevalence of Kratom consumption in our population. None of the analyzed routine hair samples were positive for mitragynine or 7‐hydroxymitragynine, providing no evidence that Kratom consumption is prevalent in the investigated population.     

Two-dimensional LC–MS/MS determination of antiretroviral drugs in rat serum and urine

A simple, rapid, reliable and highly sensitive on-line two-dimensional reversed-phase liquid chromatography–tandem mass spectrometric (2D-LC/MS/MS) method to determine antiretroviral drugs viz., abacavir (ABC), nevirapine (NVP) and indinavir (IDV) in rat serum and urine was developed and validated. The analytes were extracted on-line from rat serum and urine by a restricted access material (RAM) column and back-flushed into the reversed-phase C₁₈ column for separation by LC. Detection was carried out by ESI-MS/MS. The developed method showed good selectivity, accuracy and precision for quantification of the antiretroviral drugs in rat serum and urine. Quantification limits for abacavir and nevirapine were 4.0 ng ml⁻¹, whereas for indinavir 4.7 ng ml⁻¹. The calibration graphs were linear in the range of 4–50 ng ml⁻¹for abacavir, nevirapine and indinavir. The method was successfully applied to study the pharmacokinetics of antiretroviral in rats.     

Ultra‐fast LC–MS/MS in therapeutic drug monitoring: Quantification of clozapine and norclozapine in human plasma

A novel approach to high‐throughput, targeted liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis has been developed. A single chromatographic system can be used for the analysis of a range of 20 drugs and metabolites with a total analysis time of 36 s (one 96‐well plate of prepared samples per hour). To demonstrate the applicability of this approach to quantitative analysis, a method has been validated for the therapeutic drug monitoring of clozapine and norclozapine following automated extraction from human plasma. Chromatographic retention times were 11.4 and 12.4 s for norclozapine and clozapine, respectively (for both analytes the chromatographic peak width was less than 1 s). Comparison with a conventional LC–MS/MS method (5 min analysis time) showed excellent agreement. This new approach offers analysis times more akin to flow‐injection analysis, but is likely to be more widely applicable because of chromatographic resolution from residual matrix components and isobaric interferences.     

Development and validation of LC–MS/MS method for the determination of cyproheptadine in several pharmaceutical syrup formulations

A rapid and sensitive liquid chromatographic–tandem mass spectrometric (LC–MS/MS) method was developed and validated for the qualitative and quantitative assay of cyproheptadine (CP) in pharmaceutical samples. Diphenylpyraline hydrochloride (DPP) was used as an internal standard (IS). Two multiple reaction-monitoring (MRM) transitions for each analyte were observed: 288.1/96.1 and 288.1/191.2 for CP and 282.1/167.2 and 282.1/116.3 for DPP. The retention time of the drug was 7.29 min. The analytical method was successfully validated for linearity (1–100 ng/ml), intra-day precision, inter-day precision, and accuracy. The limit of detection (LOD) and limit of quantification (LOQ) were 0.86 and 0.98 ng/ml, respectively. The proposed method was applied to analyse the cyproheptadine content from seven different syrup formulations.     

LC−MS/MS assay for the determination of a novel anti‐fibrotic candidate mefunidone in monkey plasma and its application to a pharmacokinetics study

Mefunidone (MFD) is a promising anti‐fibrotic candidate molecule with greater anti‐fibrotic activity than pirfenidone (PFD). However, there has been no report on the methodology used for the quantification of MFD or on any investigation of its pharmacokinetics. In this study, an efficient and reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed to assay MFD in monkey plasma. This assay method was validated and applied to a pharmacokinetics study in monkeys. The lower limit of quantification of this assay was 0.1 μg·mL^?1, and the linear calibration curve was acquired with R² > 0.99 between 0.1 and 60 μg·mL^?1. The intra‐day and inter‐day precision were evaluated with coefficient of variations of 1.5%–5.8%, whereas the mean accuracy ranged from 91.7% to 106.9%. A negligible matrix effect and good recovery were obtained using this assay, with average extraction recoveries of MFD and the internal standard (IS) in the range of 85.5%–124.8% and 84.1%–94.0%, respectively. The precision of the absolute matrix effect of MFD and the IS was 1.2–3.0% and 1.2–7.3%, respectively. The samples were stable under all experimental conditions. Linear pharmacokinetics were observed for MFD in monkeys, where the exposures of MFD increased proportionally with increasing MFD doses at the range of 10–90 mg·kg^?1. Moderate elimination of MFD from the body was observed, with t_1/2 of 5–7 h, and the elimination rate of MFD was stable during multiple dosing. In conclusion, this method provides an reliable analytical approach for quantification of MFD in plasma and was successfully applied to a pharmacokinetics study in monkeys.     

Simultaneous determination of two bioactive components of Huangqi Guizhi Wuwu Decoction in rat plasma using UPLC-MS/MS and its application to a pharmacokinetic study

A rapid, sensitive and selective UPLC-MS/MS method was developed to determine paeoniflorin and astragaloside IV. This method was validated via a pharmacokinetic study using rat plasma. The internal standard was clarithromycin. A simple one-step deproteinization procedure was used to prepare plasma samples. Separation was achieved on a CAPCELL CORE ADME C₁₈ column with a gradient mobile phase consisting of solution A (water containing 0.1% formic acid) and solution B (acetonitrile) at a flow rate of 0.3 mL/min. Multiple reaction monitoring (MRM) was used with an electrospray ionization source (ESI) in positive mode. A good linear response was observed within the ranges of 0.01 to 5.00 μg/mL for paeoniflorin and 0.0001 to 0.05 μg/mL for astragaloside IV. The accuracy (RE) was within the range of –3.5% to 6.3%, and the intra- and inter-day precisions (RSD) were within 14.2%. The extraction recoveries were all above 78.9%. The pharmacokinetic study of the two analytes in rats after oral administration of Huangqi Guizhi Wuwu Decoction (HGWD) was successfully completed through this method. The method developed in this study will fill a gap in pharmacokinetic studies of HGWD.     

Enantioselective analysis of citalopram and demethylcitalopram in human whole blood by chiral LC–MS/MS and application in forensic cases

Citalopram is one of the most frequently used antidepressants in Denmark. It is marketed as a racemic mixture (50:50) of S‐ and R‐enantiomers as well as of the S‐enantiomer alone, which is the active enantiomer named escitalopram that processes the inhibitory effects. In this study, a chiral liquid chromatography–tandem mass spectrometry (LC–MS/MS) method is developed for the measurement of citalopram and demethylcitalopram enantiomers in whole blood and is applied to forensic cases. Whole blood samples (0.10 g) were extracted with butyl acetate after adjusting the pH with 2 M NaOH. The analytes were separated on a 250 × 4.6 mm Chirobiotic V, 5 μm column by isocratic elution with methanol:ammonia:acetic acid (1000:1:1) using an ultra‐high‐pressure liquid chromatography (UHPLC) system. Quantification was performed by tandem mass spectrometry (MS/MS) using multiple reaction monitoring (MRM) in the positive mode. The total chromatographic run time was 20 min. The limit of detection (LOD) and quantification (LOQ) were 0.001 and 0.005 mg/kg of all four enantiomers, respectively. Linear behaviour was obtained for all four enantiomers from LOQ to 0.50 mg/kg blood with absolute recoveries from 71 to 80%. The method showed an acceptable precision and accuracy as the obtained coefficient of variation, and bias values were ≤16% for all enantiomers. After the validation of the method, a correlation with the racemic method was assessed and found to be acceptable. Then, the method was successfully applied to authentic blood samples from forensic investigations demonstrating that escitalopram was less frequent than citalopram among all forensic cases. Copyright © 2017 John Wiley & Sons, Ltd.     

Analysis of illicit glucocorticoid levels in camel hair using competitive ELISA – Comparison with LC–MS/MS

Accurate, sensitive, and rapid screening of performance‐enhancing drugs, including glucocorticoids, is critical to combat doping in animal racing sports. Samples of urine, saliva, and serum are usually used for random screening of controlled substances; however, they tend to provide only acute usage and doping information. Hair testing has the potential to detect long‐term drug use in racing animals. In the present study, commercially available ELISA‐kits were used to rapidly screen and analyze various natural and synthetic glucocorticoids in the hair of camels. The four glucocorticoids that were screened using the competitive ELISA were hydrocortisone, dexamethasone, flumethasone, and methylprednisolone. However, comparison of the results obtained using the ELISA method with our previously published LC–MS/MS assay did not show a good correlation. The results obtained with the ELISA analysis of hair samples of 27 different camels showed that this technique consistently yielded significantly higher levels of glucocorticoids compared with the LC–MS/MS assay. This is an interesting finding and suggests that commercially available ELISA tests may overestimate the amount of glucocorticoids present in camel hair, perhaps due to specificity and cross‐reactivity issues.     

Determination of chamaechromone in rat plasma by liquid chromatography-tandem mass spectrometry: application to pharmacokinetic study

A rapid, simple and accurate method was developed for the determination of chamaechromone in rat plasma using liquid chromatography tandem mass spectrometry (LC–MS–MS). Rosuvastatin was used as the internal standard. The plasma samples were extracted by liquid–liquid extraction with ethyl acetate. Chromatographic separation was performed on Xbridge™ C₁₈ column (2.1 mm × 50 mm, 3.5 μm) with linear gradient elution using water and methanol, both of which were acidified with 0.1% aqueous formic acid. The flow rate was 0.4 mL/min and the total run time was 6 min. Detection was performed on a triple-quadrupole tandem mass spectrometer using positive ion mode electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. The MS/MS ion transitions monitored were m/z 543.3 → 198.9 and 481.9 → 258.3 for chamaechromone and rosuvastatin, respectively. Good linearity was observed over the concentration range of 8–6400 ng/mL in 0.1 mL of rat plasma. The lowest concentration (8 ng/mL) in the calibration curve was estimated as LLOQ with both deviation of accuracy and RSD of precision <20% (n = 6). Intra-assay and inter-assay variability were less than 11% in plasma. This method was successfully applied to a pharmacokinetic study of chamaechromone in rats after intravenous (5 mg/kg) and oral (100 mg/kg) administration. Following oral administration the concentration–time curve of chamaechromone exhibited a biphasic absorption profile. The maximum mean concentration in plasma (C_max, 795.9 ± 14.6 ng/L) was achieved at 11.3 ± 0.8 h (T_max) and the area under curve (AUC_0–60) was 6976.7 ± 1026.9 ng h/L. After single intravenously administration of chamaechromone, the essential pharmacokinetic parameters C_max, AUC_0–48 were 4300.7 ± 113.6 ng/L and 3672.1 ± 225.4 ng h/L, respectively. The result showed that the compound was poorly absorbed with an absolute bioavailability being approximately 8.9%.