Metabolites In Rat Blood Research Articles

LC-HRMS methods for the quantification of two artemisinin drugs and their metabolites in rat blood and plasma.

As first-line antimalarials used in the artemisinin combination therapy, artemisinin drugs exert their action inside red blood cells. However, the blood pharmacokinetic characteristics of artemisinin drugs have not been fully revealed owing to their built-in chemical instability initiated by Fe2+ released from hemoglobin, with limited information on their metabolites. In this study, liquid chromatography tandem high-resolution mass spectrometric (LC-HRMS) methods were developed for the quantification of two representative artemisinin drugs (artemisinin, ART; dihydroartemisinin, DHA) and their respective metabolite (deoxyartemisinin, D-ART; dihydroartemisinin glucuronide, DHA-Glu) in rat blood/plasma. The blood samples were pretreated with the stabilizer (0.4m potassium dichromate and 3% EDTA-2Na). The methods displayed excellent specificity, linearity, accuracy and precision for ART (17.7-709.2nm) and its metabolite D-ART (18.8-751.9nm), and the linear range was 40.0-4,000.0nm for both DHA and DHA-Glu. The methods were successfully applied to the pharmacokinetic studies of ART and DHA in rats. The blood-to-plasma ratio was 0.8-1.5 for ART, 1.0-1.5 for D-ART, 1.2-2.2 for DHA and 0.9-1.3 for DHA-Glu, which was time dependent. The results indicated that artemisinin drugs and their metabolites showed a high but different blood-to-plasma ratio, which should be considered when optimizating their dosing regimens or evaluating their clinical outcomes.

Simultaneous determination of cordycepin and its metabolite 3'-deoxyinosine in rat whole blood by ultra-high-performance liquid chromatography coupled with Q Exactive hybrid quadrupole orbitrap high-resolution accurate mass spectrometry and its application to accurate pharmacokinetic studies.

Cordycepin from Cordyceps possesses excellent pharmacological properties, including anti-inflammation and anti-tumor effects, therefore representing a potential alternative medicine. However, doubts about the pharmacokinetic results of cordycepin had been raised in the previous study due to its rapid deamination. The organic solvent methanol was immediately added to terminate the degradation of cordycepin in anticoagulated blood samples and enable the accurate evaluation of pharmacokinetics in vivo. A sensitive and selective ultra-high-performance liquid chromatography coupled with Q Exactive hybrid quadrupole orbitrap high-resolution accurate mass spectrometry method was developed and validated to simultaneously determine cordycepin and its deamination metabolite 3'-deoxyinosine using 2-chloroadenosine as an internal standard in rat whole blood. The calibration curves of cordycepin and 3'-deoxyinosine showed excellent linearity within the concentration range of 1.05-10 000.00 ng/ml with acceptable accuracy, precision, selectivity, recovery, matrix effect, and stability. This method was successfully applied to the pharmacokinetic study of cordycepin and its metabolite in rat blood. The effect of the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride on the pharmacokinetics of cordycepin was investigated. In summary, the reliable pharmacokinetic parameters of cordycepin and its deamination metabolite 3'-deoxyinosine in rat blood were successfully elucidated. Erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride considerably prolonged the half-life of cordycepin in vivo.

LC-MS/MS Method for Determination of Hydroxychloroquine and Metabolites: Application in a Pharmacokinetic Study.

Hydroxychloroquine (HCQ) was originally used as an antimalarial and immunomodulation drug. We developed and validated a simple and sensitive ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for simultaneous quantitation of HCQ and its three metabolites in rat blood, and reported their pharmacokinetic parameters. The chromatographic separation and detection of analytes were achieved within 4 min on ZORBAX SB-C8 (3.5 μm, 2.1 × 150 mm) column with gradient elution, and the flow rate was 0.25 mL/min. Simple protein precipitation was successfully applied for sample pretreatment. The HCQ displays a good linearity in the range of 2.0–5000.0 ng/mL, and the three metabolites also show good linearity ranging from 1.0 to 2500.0 ng/mL, with all correlation coefficients (R2) better than 0.98. In conclusion, this rapid, sensitive method was successfully developed, validated, and then applied to a pharmacokinetic study of HCQ in rat model in high dose. The results of the pharmacokinetic study presented an average half-life time 21.14 ± 10.31 h (mean ± SD) of HCQ, which is much shorter in human compared to that in mice. For the three metabolites, longer half-life times (approximately 100 h) were shown in rat.

A Study on Acetylglutamine Pharmacokinetics in Rat Blood and Brain Based on Liquid Chromatography-Tandem Mass Spectrometry and Microdialysis Technique.

Acetylglutamine (NAG) is the derivative of glutamine, which is the richest free amino acid in the human body. In this work, a novel reliable method of the combination of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and microdialysis (MD) technique for the evaluation of NAG and its metabolites γ-aminobutyric acid (GABA) and glutamic acid (Glu) in rat blood and brain was proposed. A Zorbax SB-C18 column (2.1 × 100 mm, 3.5 μM) was applied to separate the analytes. The mobile phase was acetonitrile-water (70:30, v/v) containing 5 mM ammonium acetate and the flow rate was 0.3 ml/min. Based on the multiple reaction monitoring (MRM) mode of positive ion, the precursors of product ions chosen for NAG, Glu, GABA, and N-carbamyl-L-glutamic (NCG, IS) were (m/z) 189.1→130.0, 148.0→84.1, 104→87.1, and 191.0→130.1, respectively. All the validation data, including precision, accuracy, inter-day repeatability, matrix effect, and stability, were within the acceptable ranges according to the reference of Bioanalytical Method Validation Guidance for Industry (2018). Rats with microdialysis probes inserted into jugular vein and hippocampus were administered the low (75 mg/kg, NAG-L), medium (150 mg/kg, NAG-M), and high (300 mg/kg, NAG-H) doses of NAG and 10 ml/kg Guhong injection (GHI) by tail vein, respectively. In the blood test, the Cmax values of NAG-L group were markedly lower (P < 0.01) than those of NAG-M, NAG-H, and GHI groups, respectively. No differences were observed between NAG-M and GHI groups, while the Cmax values in GHI group were significantly upgraded compared with NAG-H group. There were notable differences in the Cmax values of NAG in brain dialysate after administration of NAG and GHI. The drug distribution coefficients of NAG, Glu, GABA in brain and blood at low, medium, high doses of NAG and GHI groups were 13.99, 27.43, 34.81, 31.37; 11.04, 59.07, 21.69, 2.69%; 212.88, 234.92, 157.59, and 102.65%, respectively. Our investigation demonstrates that NAG and its related metabolites in rat blood and brain can be simultaneously measured according to the above proposed method. Meanwhile, NAG has easy and dose-dependently access to the blood-brain barrier and exhibits a medium retention time in rat.

Identification of saponins from Panax notoginseng in metabolites of rats

UPLC-QTOF-MS/MS was used to identify metabolites in rat blood, urine and feces after the administration of n-butanol extract derived from steamed notoginseng. The metabolic process of saponins came from steamed notoginseng was analyzed. The metabolites were processed by PeakView software, and identified according to the structural characteristics of prototype compounds and the accurate qualitative and quantitative changes of common metabolic pathways. Four saponins metabolites were identified based on MS/MS information of metabolites, namely ginsenoside Rh₄, Rk₃, Rk₁, Rg₅,and their 15 metabolites were verified. The metabolic pathways of the four ginsenosides in n-butanol extract included glucuronidation, desugar, sulfation, dehydromethylation, and branch loss. The metabolites of main active saponin components derived from steamed Panax notoginseng were analyzed from the perspective of qualitative analysis. And the material basis for the efficacy of steamed notoginseng was further clarified.

Assessment of a Maslinic Acid Derivative and its Metabolite in Rat Blood by Liquid Chromatography Coupled with Mass Spectrometry

A new rapid high-throughput liquid chromatography coupled with tandem mass spectrometry method (LC-MS/MS) was developed for the blood assessment of a maslinic acid derivative (Benzyl (2a, 3b) 2,3-diacetoxy-olean-12-en-28-amide) and its metabolite. Separation was performed using a Zorbax SB-C18 column with a mobile phase composition of methanol and 0.2% formic acid in water (78:22, v/v) in isocratic flow, with a flow rate of 0.6 mL/min. Detection was performed by multiple reaction monitoring (MRM) mode, monitoring the transitions 338.3; 526.6; 544.6; 527.5; 545.5 m/z derived from 646.6 m/z for the maslinic acid derivative and 409; 338.3; 203; 205; 526.5 m/z derived from 562.6 m/z for its metabolite, using atmospheric pressure chemical positive ionisation source. Single-step protein precipitation with methanol was used for preparation of rat blood samples. The method was validated with respect to selectivity, linearity (r ] 0.9937), within-run and between-run precision (CV [ 12.0%) and accuracy (bias [ 7.9%) over the ranges of 20.5 - 656 ng/mL blood for maslinic acid derivative, and 20 - 640 ng/mL blood for maslinic acid derivative metabolite. The analytical method is simple, fast, selective and is suitable for bioanalysis of maslinic acid derivative and its metabolite from rat blood.

Simultaneous quantification method for comparative pharmacokinetics studies of two major metabolites from geniposide and genipin by online mircrodialysis-UPLC-MS/MS.

Genipin-1-o-glucuronic acid and genipin-monosulfate are two major metabolites from geniposide and genipin. Based on diabetic rat model, we developed a simultaneous quantification method to investigate their comparative pharmacokinetics by online mircrodialysis-ultra performance liquid chromatography-mass spectrometry (MD-UPLC-MS/MS) without their standard compounds. Online microdialysis sampling could avoid unexpected contamination or degradation of the analytes during the storage and transfer steps. Combined with good sensitivity, selectivity and selectivity of UPLC-MS/MS, online MD-UPLC-MS/MS method could real-timely monitor metabolites in rat blood for quantitative analysis. Our research found that AUC0→t of genipin-1-o-glucuronic acid and genipin-monosulfate in blood of diabetic group were 17.68 and 7.58 times than those in normal group, respectively, and AUC0→t of genipin-1-o-glucuronic acid was 2.28 times than that of genipin-monosulfate in blood of diabetic group, which revealed the effect of diabetes on the pharmacokinetic properties of the two metabolites. This study not only provides an approach for pharmacokinetic studies for various metabolites from herb medicines, but also can predict druggability of their bioactive metabolites. The insight obtained should facilitate drug development and toxicity research.

Di-(2-propylheptyl) phthalate (DPHP) and its metabolites in blood of rats upon single oral administration of DPHP

Di-(2-propylheptyl) phthalate (DPHP) does not act as a reproductive toxicant or endocrine disruptor in contrast to other phthalates. Considering adverse effects of phthalates to be linked to their metabolism, it was the aim of the present study to investigate in the rat the blood burden of DPHP and its metabolites as a basis for understanding the toxicological behavior of DPHP. Rats were administered single oral doses of DPHP of 0.7 and 100mg/kg body weight. Concentration-time courses of DPHP and metabolites were monitored in blood. The areas under the concentration-time curves in blood (AUCs), normalized for the dose of DPHP, showed the following order: DPHP<mono-(2-propyl-6-oxoheptyl) phthalate<mono-(2-propyl-6-hydroxyheptyl) phthalate=mono-(2-propylheptyl) phthalate<mono-(2-propyl-6-carboxyhexyl) phthalate (cx-MPHP). Glucuronidation of the monoesters accounted for less than 5% of total compounds. The elimination half-lives of the compounds ranged from 2.3h (DPHP) to 8.2h (cx-MPHP). The normalized AUCs of the metabolites were lower at the high dose of DPHP than at the low one indicating saturation kinetics of intestinal DPHP hydrolysis. The absence of toxicity to reproduction of DPHP may be related to the comparatively low bioavailability of the parent compound and its metabolites.

Pharmacokinetics of H002, a novel S1PR1 modulator, and its metabolites in rat blood using liquid chromatography–tandem mass spectrometry

A rapid and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of H002 and its phosphorylated metabolite, H002-P and hydroxylated metabolite H002-M, in rat blood. H001, an analogue of H002, was used as the internal standard. Blood samples were prepared by simple protein precipitation. The analytes and internal standard were separated on a Zorbax SB-C18 column with a gradient mobile phase consisting of methanol and water containing 0.1% formic acid at a flow rate of 0.2mL/min with an operating temperature of 20°C. The detection was performed on a triple quadrupole tandem mass spectrometer with positive electrospray ionization in multiple-reaction monitoring mode. Linear detection responses were obtained from 0.2–100ng/mL for H002 and H002-M, while 0.5–100ng/mL for H002-P. The intra- and inter-day precision (RSD%) was within 11.76%, with the accuracy (RE%) ranging from –9.84% to 9.12%. The analytes were shown to be stable during sample storage, preparation and analytic procedures. The method was applied to determine the pharmacokinetics of H002 in rats, and a preliminary study showed that the pharmacokinetics of H002 correlated with its biological effect on peripheral blood lymphocytes.

Synthesis, identification, and biological activity of metabolites of two novel selective S1P1 agonists

SYL927 and SYL930 are selective S1P1 agonists under preclinical development. However, during their pharmacokinetic studies we detected two metabolites in rat blood that were tentatively identified as monohydroxylated metabolites of SYL927 and SYL930 based on LC–MS/MS data. In this study, we designed and synthesized possible monohydroxylated products 6a–e and used them as references to confirm the structures of the two metabolites detected by LC–MS/MS. We also evaluated the in vitro and in vivo biological activities of these two metabolites.

Quantitative determination of 2-amino-2-(2-(4'-(2-propyloxazol-4-yl)-[1,1'-biphenyl]-4-yl)ethyl)propane-1,3-diol and its active phosphorylated metabolite in rat blood by LC-MS/MS and application to PK/PD analysis.

A sensitive and specific LC-MS/MS method was developed and validated for simultaneous determination of 2-amino-2-(2-(4'-(2-propyloxazol-4-yl)-[1,1'-biphenyl]-4-yl)ethyl)propane-1,3-diol (SYL930) and its active phosphate metabolite (SYL930-P) in rat blood using SYL927, an analogue of SYL930 as the internal standard. Blood samples were prepared by a simple protein precipitation with acetonitrile. The chromatographic separation was performed on a ZorbaxSB-C18 column (3.5μm, 2.1 × 100mm) with a gradient mobile phase of methanol/water containing 0.1% formic acid (v/v) at a flow rate of 0.2mL/min. The detection was carried out on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) in multiple reactions monitoring mode (MRM). The monitored transitions were 381.2 → 364.2 for SYL930, 461.2 → 334.2 for SYL930-P, and 367.1 → 350.4 for the internal standard, respectively. Good linearity was obtained for the analytes over the range of 0.2-100ng/mL for SYL930 and 0.5-100ng/mL for SYL930-P. The lower limits of quantitation (LLOQs) for SYL930 and SYL930-P were 0.2 and 0.5ng/mL, respectively. The intra-day and inter-day precisions (RSD, %) of analytes were within 9.87%, and the accuracy (RE, %) ranged from -7.04 to 13.15%. The mean recoveries for two compounds in rat blood were 87.9-109%. The analytes were proved to be stable during all sample storage, preparation, and analytic procedures. The validated method was successfully applied to pharmacokinetic and PK/PD studies of SYL930 and SYL930-P in rats after oral administration of SYL930. Graphical Abstract Quantitative determination of SYL930 and its active phosphorylated metabolite in rat blood by LCMS/MS and application to PK/PD analysis.

Quantitation of celecoxib and four of its metabolites in rat blood by UPLC-MS/MS clarifies their blood distribution patterns and provides more accurate pharmacokinetics profiles.

A sensitive UPLC-MS/MS method was established and validated for the quantitation of celecoxib and its metabolites in rat blood. The analytes were extracted from rat blood samples by a salting-out liquid-liquid extraction method followed by the UPLC chromatography. The mass analysis of effluent was performed on an API 5500 Qtrap mass spectrometer via multiple reactions monitoring (MRM). The linear response ranges were 0.3-20000nM for celecoxib, and 1.2-20000nM, 0.3-20000nM, 2.0-2000nM, 1.5-6000nM for its metabolites carboxycelecoxib (M2), hydroxycelecoxib (M3), hydroxycelecoxib glucuronide (M1), and carboxycelecoxib glucuronide (M5), respectively. The inter-day and intra-day accuracies were within 85-115%, and the inter-day and intra-day precision were acceptable (<12%) for all analytes. Recoveries were above 70% and no obvious matrix effects were observed. The validated UPLC-MS/MS method was successfully applied to a pharmacokinetics study of oral celecoxib (20mg/kg) in Sprague-Dawley rats, and the rat blood concentrations (0-48h) of celecoxib and two of its metabolites M2 and M3 were successfully determined. Using the same method, we also showed preferential distributions of celecoxib, M2 and M3 in the blood cells as compared to the plasma. In conclusion, our results showed that our validated LC-MS/MS method can be successfully used for the pharmacokinetic studies of celecoxib and that the blood cells are a very important compartment for this drug such that profiles of celecoxib and its metabolites in whole blood will be more comprehensive and accurate representation of their profiles in vivo than the plasma.

Simultaneous determination of nicotine and its nine metabolites in rat blood utilizing microdialysis coupled with UPLC-tandem mass spectrometry for pharmacokinetic application.

To develop a simple and rapid method for the simultaneous determination of nicotine and its nine metabolites in rat blood, an in vivo microdialysis sampling technique coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established for quantitation and characterization of the pharmacokinetics of nicotine and its metabolites. Microdialysis probes were inserted into the jugular vein of Sprague Dawley rats, and dialysates were collected after nicotine (0.5 mg/kg, i.p.) administration. Target analytes and corresponding deuterated internal standards were separated on a hydrophilic interaction liquid chromatography column (HILIC BEH 2.1. × 150 mm, 1.7 μm) and detected by UPLC-MS/MS under multiple reaction monitoring mode. The limits of quantification for nicotine and its nine metabolites ranged from 0.039 to 0.46 ng/mL. Intra- and inter-day precision and accuracy were well within the predefined limits of acceptability (<11 %). Pharmacokinetic results showed that the mean half-lives of nicotine, cotinine, nornicotine, norcotinine, nicotine-N'-oxide, cotinine-N'-oxide, trans-3'-hydroxy-cotinine, nicotine-N-glucuronide, cotinine-N-glucuronide, and trans-3'-hydroxy-cotinine-O-glucuronide in rat plasma were 63, 291, 175, 440, 251, 451, 322, 341, 488, and 516 min, respectively. The blood concentration-time profiles of nicotine and its nine metabolites indicate that nicotine is rapidly consumed after the administration and subsequently cotinine is generated as the main metabolite; meanwhile, cotinine and other eight minor metabolites exhibit longer retention times in rat body.

Determination of cis-permethrin, trans-permethrin and associated metabolites in rat blood and organs by gas chromatography–ion trap mass spectrometry

An analytical method was developed to measure cis-permethrin and trans-permethrin in different biological rat matrices and fluids (whole blood, red blood cells, plasma, brain, liver, muscle, testes, kidneys, fat and faeces). The method was also suitable for the simultaneous quantification of their associated metabolites [cis-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (cis-DCCA), trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (trans-DCCA) and 3-phenoxybenzoic acid (3-PBA)] in blood (whole blood, red blood cells, plasma) and liver. The target analytes were derivatised in samples using a methanolic/hydrochloric acid solution and then extracted with toluene. The analysis was performed by gas chromatography, and detection using ion trap tandem mass spectrometry. The selectivity obtained for complex matrices such as rat organs allowed the use of a purification step to be avoided for most of the matrices investigated. In the case of fat, where permethrin is suspected to accumulate, a dedicated purification step was developed. In fluids, the limits of quantification were at the 50 ng/mL level for the parent compounds and 3-PBA and at 25 ng/mL for cis-DCCA and trans-DCCA. For solid matrices excluding fat, the limits of quantification ranged from 50 ng/g for muscle to 100 ng/g for brain and testes for both cis-permethrin and trans-permethrin. The extraction recoveries ranged primarily between 80 and 120% for the matrix tested. The stability of blood samples was tested through the addition of 1% v/v formic acid. The methods developed were applied in a toxicokinetic study in adult rats. cis-Permethrin and the metabolites were detected in all corresponding matrices, whereas trans-permethrin was detected only in blood, plasma and faeces.

An effective method for determining the ingredients of Shuanghuanglian formula in blood samples using high‐resolution LC–MS coupled with background subtraction and a multiple data processing approach

Shuanghuanglian formula (SF) is a combination of Flos lonicerae japonicae, Radix scutellariae, and Fructus forsythiae, commonly used to treat viral or bacterial infections. However, the constituents absorbed into the blood after oral administration of SF are difficult to determine and thus remain unclear. Here, we report the application of an accurate background subtraction and multiple data processing approach (Bs-Mpa) for the comprehensive detection of compounds of SF in vivo. A sensitive and reliable ultra-performance LC coupled with ESI quadrupole TOF MS (UPLC-ESI-Q-TOF-MS) approach coupled with Bs-Mpa, which is implemented in the Strip tool from UPLC to remove nonrelated ion signals from accurate mass LC-MS data, was established to characterize the chemical constituents and rat metabolites of SF. In the loading plot of the principal component analysis, 68 ions of interest were extracted from blood samples, among them, 39 absorbed prototype components of SF and 29 metabolites were identified in vivo. It is concluded that the integrative Bs-Mpa method can be successfully applied for the rapid discovery of multiple components from a traditional Chinese medicine. The above challenge was addressed by using the proposed Bs-Mpa method and it was particularly suitable for applying to the global characterization of the constituents or metabolites in rat blood after oral administration of other well-known formulae.

Mephedrone pharmacokinetics after intravenous and oral administration in rats: relation to pharmacodynamics

Mephedrone (4-methylmethcathinone) is a still poorly known drug of abuse, alternative to ecstasy or cocaine. The major aims were to investigate the pharmacokinetics and locomotor activity of mephedrone in rats and provide a pharmacokinetic/pharmacodynamic model. Mephedrone was administered to male Sprague-Dawley rats intravenously (10 mg/kg) and orally (30 and 60 mg/kg). Plasma concentrations and metabolites were characterized using LC/MS and LC-MS/MS fragmentation patterns. Locomotor activity was monitored for 180-240 min. Mephedrone plasma concentrations after i.v. administration fit a two-compartment model (α = 10.23 h(-1), β = 1.86 h(-1)). After oral administration, peak mephedrone concentrations were achieved between 0.5 and 1 h and declined to undetectable levels at 9 h. The absolute bioavailability of mephedrone was about 10% and the percentage of mephedrone protein binding was 21.59 ± 3.67%. We have identified five phase I metabolites in rat blood after oral administration. The relationship between brain levels and free plasma concentration was 1.85 ± 0.08. Mephedrone induced a dose-dependent increase in locomotor activity, which lasted up to 2 h. The pharmacokinetic-pharmacodynamic model successfully describes the relationship between mephedrone plasma concentrations and its psychostimulant effect. We suggest a very important first-pass effect for mephedrone after oral administration and an easy access to the central nervous system. The model described might be useful in the estimation and prediction of the onset, magnitude, and time course of mephedrone pharmacodynamics as well as to design new animal models of mephedrone addiction and toxicity.

Development and validation of a highly sensitive UPLC-MS/MS method for simultaneous determination of aconitine, mesaconitine, hypaconitine, and five of their metabolites in rat blood and its application to a pharmacokinetics study of aconitine, mesaconitine, and hypaconitine

A rapid, specific and sensitive method was developed for the simultaneous determination of eight Aconitum alkaloids: aconitine (AC), mesaconitine (MA), hypaconitine (HA), benzoylaconine (BAC), benzoylmesaconine (BMA), benzoylhypaconine (BHA), aconine and mesaconine in rat blood by ultra-performance liquid chromatography coupled tandem mass spectrometry (UPLC-MS/MS).The UPLC-MS/MS system coupled with an electrospray ionization (ESI) source was operated in a positive mode via multiple-reaction monitoring (MRM). Samples were treated with methanol to remove protein prior to analysis by UPLC-MS/MS. The analytes were separated with a Waters C18 column (1.7 µm, 50 × 2.1 mm) and a gradient elution using acetonitrile and 0.1% formic acid-water as the mobile phases.The linear response range was from 0.125 to 1000 nmol/L for these eight alkaloids and the correlation coefficients (r2 values) were all higher than 0.997. The method was validated with respect to precision, accuracy, recovery, matrix effect, carryover effect and sample stability, and found to be within the acceptable limits.The developed and validated method was successfully applied to simultaneously determine the eight Aconitum alkaloids in rats blood after intravenous administration of a mixture of AC, MA and HA.

Bioanalytical Determination of Unstable Endogenous Small Peptides: Rfrp3 and its Metabolites in Rat Blood

Targeting the gonadotropin-releasing hormone pathway for the treatment of endometriosis leads to an interest in monitoring for endogenous modulators of this pathway (RFRP3 and kisspeptin) as baseline controls for treatment development. Stabilization of RFRP3 was shown to be extremely difficult in a highly enzymatically active matrix, such as rat blood. Sample denaturing with solvent at collection was necessary due to enzyme inhibition being unsuccessful at stabilization leading to difficulties in sample processing. Monitoring multiple fragments formed in blood can aid in profiling these peptides once in-source conversion is controlled. generic high-sensitivity LC-MS/MS assay was developed for RFRP3 and the fragments formed from it in whole blood. Use of 2D chromatography circumvents concentration and retention issues related to small fragments with a normal flow setup, making a more open-access approach feasible.

Analysis of methylene blue and its metabolites in blood by capillary electrophoresis/electrospray ionization mass spectrometry

A method for the determination of methylene blue (MB) and its metabolites (azure A, azure B and azure C) in rat blood by CE-electrospray ionization mass spectrometry (CE-ESI-MS) was developed in this paper. Different analytical parameters were investigated in detail such as pH and concentration of separation buffer, and ESI-MS instrumental parameters. Under the optimum conditions, MB and its metabolites were separated and detected in 27.3 min. LODs (defined as S/N=3) of this method were 0.22, 0.25, 0.10 and 0.30 μg/mL for MB, azure A, azure B and azure C, respectively. To get a satisfactory extraction efficiency of MB and its metabolites in rat blood, different extraction solutions were studied. By using this method, MB and its metabolites (azure A, azure B and azure C) were successfully analyzed in rat blood samples.

In situ derivatization/solid‐phase microextraction coupled with gas chromatography/negative chemical ionization mass spectrometry for the determination of trichloroethylene metabolites in rat blood

An in situ derivatization solid-phase microextraction (SPME) method has been developed for the determination of the trichloroethylene (TCE) metabolites, trichloroacetic acid (TCA), dichloroacetic acid (DCA) and trichloroethanol (TCOH), in rat blood. The analytical procedure involves derivatization of TCA and DCA to their ethyl esters with acidic ethanol, headspace sampling using SPME, and gas chromatography/negative chemical ionization mass spectrometry (GC/NCI-MS) determination. Parameters affecting both derivatization efficiency and the headspace SPME procedure, such as the concentration of sulfuric acid, amount of ethanol, derivatization-extraction temperature and time, sample preheating time, agitator speed and desorption conditions, were optimized. The method showed good linearity over the range of 1-1000 ng/mL in rat blood for each metabolite with correlation coefficients (R(2)) higher than 0.99. The intra-day and inter-day precision and accuracy were less than 10%. The relative recoveries for all analytes were greater than 84%. Validation results demonstrated that selected ion monitoring of the (35)Cl and (37)Cl isotopes using NCI resulted in reliable and sensitive quantitation of all three TCE metabolites. This validated method was successfully applied to study the toxicokinetic behavior of TCE metabolites following a 1 mg/kg oral dose of TCE.