Identification of degradation products of brivaracetam using liquid chromatography quadrupole time-of-flight tandem mass spectrometry: Degradation pathway elucidation.

RATIONALE: Pyrrolidone-based drugs find widespread use in treating conditions such as epilepsy and Alzheimer's disease, and in various other medical applications. Brivaracetam, the latest generation of pyrrolidone drugs, has exhibited significant promise owing to chemical structure modifications. Its affinity to the SV2A receptor is double that of the previous-generation drug, levetiracetam. Consequently, brivaracetam holds substantial potential for diverse applications. As a novel drug not yet included in the pharmacopeias of developed nations, comprehensive analysis and research are necessary to guarantee its safe utilization in clinical settings. METHODS: A liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC/QTOFMS) method has been developed to effectively separate, identify and characterize both the degradation products and process-related substances of brivaracetam. Stress testing of the sample was carried out following the guidelines outlined in ICH Q1A(R2). The structures of these impurities were identified through positive electrospray ionization QTOF high-resolution MS and NMR spectroscopy. Additionally, the formation mechanism of each degradation product is thoroughly discussed. RESULTS: Under the analytical conditions outlined in this paper, brivaracetam and its degradation products were effectively separated. Thirteen degradation products were detected and characterized, shedding light on their origins and degradation pathways. Among these, three degradation products align with previously reported impurities, and two unreported degradation products were synthesized and confirmed through NMR spectroscopy. The stress testing results revealed the instability of brivaracetam under acidic, alkaline, oxidative and thermal stress conditions, while it exhibited relative stability under photolytic stress conditions. CONCLUSION: The study developed an analytical method for brivaracetam that enabled the effective detection and separation of brivaracetam and its 13 degradation products. This method addresses a gap in both current domestic and foreign drug standards. The structures of all the major degradation products were characterized by high-resolution LC/QTOFMS, which is essential for quality control during the drug production process, stability evaluation and the establishment of proper storage conditions.

Metabolism of ADB-FUBIATA in zebrafish and pooled human liver microsomes investigated by liquid chromatography-high-resolution mass spectrometry.

RATIONALE: ADB-FUBIATA is one of the most recently identified new psychoactive substance (NPS) of synthetic cannabinoids. The co-use of in vitro (human liver microsomes) and in vivo (zebrafish) models offers abundant metabolites and may give a deep insight into the metabolism of NPS. METHODS: In vivo and in vitro metabolic studies of new synthetic cannabinoid ADB-FUBIATA were carried out using zebrafish and pooled human liver microsome models. Metabilites were structurally characterized by liquid chromatography-high-resolution mass spectrometry. RESULTS: In total, 18 metabolites were discovered and identified in the pooled human liver microsomes and zebrafish, including seventeen phase I metabolites and one phase II metabolite. The main metabolic pathways of ADB-FUBIATA were hydroxylation, dehydrogenation, N-dealkylation, amide hydrolysis, glucuronidation, and combination thereof. CONCLUSION: Hydroxylated metabolites can be recommended as metabolic markers for ADB-FUBIATA because of the structural characteristics and high intensity. These metabolism characteristics of ADB-FUBIATA were useful for its further forensic or clinical related investigations.

Metabolite characterisation of the peptide-drug conjugate LN005 in liver S9s by UHPLC-Orbitrap-HRMS.

LN005 is a peptide-drug conjugate (PDC) targeting glucose-regulated protein 78 (GRP78) to treat several types of cancer, such as breast, colon, and prostate cancer.As a new drug modality, understanding its metabolism and elimination pathways will help us to have a whole picture of it. Currently, there are no metabolic studies on LN005; therefore, this study aimed to investigate the metabolism of LN005, clarify its metabolic profile in the liver S9s of different species, and identify the major metabolic pathways and differences between species.The incubation samples were measured by ultra-high performance liquid chromatography combined with orbitrap tandem mass spectrometry (UHPLC-Orbitrap-HRMS).The results showed that LN005 was metabolised by liver S9s, and four metabolites were identified. The main metabolic pathway of LN005 in liver S9s was oxidative deamination to ketone or hydrolysis. Similar metabolic profiles were observed in mouse, rat, dog, monkey, and human liver S9s, indicating no differences between these four animal species and humans.This study provides information for the structural modification and optimisation of LN005 and affords a reference for subsequent animal experiments and human metabolism of other PDCs.

Kelp as a biomonitor of persistent organic pollutants in coastal areas of China: Contamination levels and human health risk.

Kelp, the brown alga distributed in coastal areas all over the world, is also an important medicine food homology product in China. However, the levels and profiles of persistent organic pollutants (POPs) in kelp have not been thoroughly investigated to date. Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and emerging bromine flame retardants (eBFRs) were evaluated in 41 kelp samples from the main kelp producing areas in China. The concentrations of total PCBs, PBDEs and eBFRs were in the range of 0.321-4.24 ng/g dry weight (dw), 0.255-25.5 ng/g dw and 3.00 × 10-3-47.2 ng/g dw in kelp, respectively. The pollutant pattern was dominated by decabromodiphenyl ethane (DBDPE, 13.0 ± 11.7 ng/g dw) followed in decreasing order by BDE-209 (2.74 ± 4.09 ng/g dw), CB-11 (1.32 ± 1.06 ng/g dw). The tested results showed that kelp could reflect the pollution status of PCBs, PBDEs and eBFRs, indicating the suitability of kelp as a biomonitor of these harmful substances. Finally, the data obtained was used to evaluate human non-cancer and cancer risks of PCBs and PBDEs via kelp consumption for Chinese. Though the calculated risk indices were considered acceptable according to the international standards even in the worst scenarios, the POPs levels in kelp should be monitored continuously as a good environmental indicator.

Application of the metal ions as potential population biomarkers for wastewater-based epidemiology: estimating tobacco consumption in Southern China.

Wastewater-based epidemiology (WBE) is an objective approach for the estimation of population-level exposure to a wide range of substances, in which the use of a population biomarker (PB) could significantly reduce back-calculation errors. Although some endogenous or exogenous compounds such as cotinine and other hormones have been developed as PBs, more PBs still need to be identified and evaluated. This study aimed to propose a novel method to estimate population parameters from the mass load of metal ion biomarkers in wastewater, and estimate the consumption of tobacco in 24 cities in Southern China using the developed method. Daily wastewater samples were collected from 234 wastewater treatment plants (WWTPs) in 24 cities in Southern China. Atomic absorption spectroscopy (AAS) was applied to determine the concentrations of common health-related metal ions in wastewater, including sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), iron (Fe), and zinc (Zn), and compared them with the daily mass load of cotinine corresponding to catchment populations. The concentrations of cotinine in wastewater samples were measured using liquid chromatography-tandem mass spectrometry. There were clear and strong correlations between the target metal ion equivalent population and census data. The correlation coefficients (R) were RK = 0.78, RNa = 0.66, RCa = 0.81, RMg = 0.77, and RFe = 0.69, at p < 0.01 and R2 > 0.6. Subsequently, the combination of WBE and metal ion PBs was used to estimate tobacco consumption. Daily consumption of nicotine was estimated to be approximately 1.76 ± 1.19 mg/d/capita, equivalent to an average of 13.0 ± 8.75 cigarettes/d being consumed by smokers. The data on tobacco consumption in this study were consistent with those in traditional surveys in Southern China. The metal ion potassium is an appropriate PB for reflecting the real-time population and could be used to evaluate the tobacco consumption in WBE study.

Gemcitabine enhances pharmacokinetic exposure of the major components of Danggui Buxue Decoction in rat via the promotion of intestinal permeability and down-regulation of CYP3A for combination treatment of non-small cell lung cancer.

CONTEXT: Danggui Buxue Decoction (DBD), a traditional Chinese medicine formula, has the potential to enhance the antitumor effect of gemcitabine in non-small cell lung cancer (NSCLC) treatment by increasing gemcitabine's active metabolites. However, whether gemcitabine affects the pharmacokinetics of DBD's major components remains unclear. OBJECTIVE: This study evaluates the herb-drug interaction between DBD's major components and gemcitabine and validates the underlying pharmacokinetic mechanism. MATERIALS AND METHODS: The pharmacokinetics of 3.6 g/kg DBD with and without a single-dose administration of 50 mg/kg gemcitabine was investigated in Sprague-Dawley rats. The effects of gemcitabine on intestinal permeability, hepatic microsomal enzymes in rat tissues, and CYP3A overexpressing HepG2 cells were determined using western blot analysis. RESULTS: The combination of gemcitabine significantly altered the pharmacokinetic profiles of DBD's major components in rats. The Cmax and AUC of calycosin-7-O-ß-d-glucoside notably increased through sodium-glucose transporter 1 (SGLT-1) expression promotion. The AUC of ligustilide and ferulic acid was also significantly elevated with the elimination half-life (t1/2) prolonged by 2.4-fold and 7.8-fold, respectively, by down-regulating hepatic CYP3A, tight junction proteins zonula occludens-1 (ZO-1) and occludin expression. DISCUSSION AND CONCLUSIONS: Gemcitabine could modulate the pharmacokinetics of DBD's major components by increasing intestinal permeability, enhancing transporter expression, and down-regulating CYP3A. These findings provide critical information for clinical research on DBD as an adjuvant for NSCLC with gemcitabine and help make potential dosage adjustments more scientifically and rationally.

Characterization of structurally related peptide impurities using HPLC-QTOF-MS/MS: application to Cbf-14, a novel antimicrobial peptide.

Cbf-14 (RLLRKFFRKLKKSV), a designed antimicrobial peptide derived from the cathelicidin family, is effective against drug-resistant bacteria. Structurally related peptide impurities in peptide medicines probably have side effects or even toxicity, thus impurity profiling research during the entire production process is indispensable. In this study, a simple liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method using a quadrupole time-of-flight (Q-TOF) mass spectrometer was developed for separation, identification, and characterization of structurally related peptide impurities in Cbf-14. A total of one process-related impurity and thirty-two degradation products were identified, and seven of them have been synthesized and confirmed. These impurities have not been declared in custom synthetic peptides. The degradation products were divided into five categories: fifteen Cbf-14 hydrolysates, five Cbf-14 isomers, four acetyl-Cbf-14 isomers, two aldimine derivatives, and six oxidized impurities. Combined with the peptide synthesis and the stress-testing studies, the origins and the formation mechanisms of these impurities were elucidated, which provides a unique insight for the follow-up quality study of Cbf-14 and other peptide products.

Simultaneous determination of nirmatrelvir and ritonavir in human plasma using LC-MS/MS and its pharmacokinetic application in healthy Chinese volunteers.

Paxlovid, a copackaged medication of nirmatrelvir tablets (150 mg) and ritonavir tablets (100 mg) developed by Pfizer, is one of the first orally accessible COVID-19 antiviral medicines to be approved for emergency usage. In this research, an efficient LC-MS/MS method for simultaneous determination of nirmatrelvir and ritonavir in human plasma was established and validated with remdesivir as an internal standard. Chromatographic separations were carried out on a Thermo BDS Hypersil C18 column (4.6 × 100 mm, 2.4 µm) using deionized water and methanol as mobile phase, both added with 0.1% (v/v) formic acid. Based on the positive electrospray ionization mode, nirmatrelvir and ritonavir were analyzed by selective reaction monitoring. Excellent precision, accuracy, recovery, and linearity were demonstrated, covering the range of 50-5000 ng/mL for nirmatrelvir and 10-1000 ng/mL for ritonavir. Then, the established method was used for determining the pharmacokinetic profile of Paxlovid in healthy Chinese volunteers. The pharmacokinetic parameters, including Cmax , Tmax , t1/2 , and AUC0 - ∞ of Western volunteers, correspond well with the results of this pharmacokinetic investigation.

Impurity profiling of alfentanil hydrochloride by liquid chromatography/quadrupole time-of-flight high-resolution mass spectrometric techniques for drug enforcement.

RATIONALE: Fentanyl and its analogues play important roles in the hospital and clinic setting as anesthetics. However, illicitly manufactured fentanyl as well as the new psychoactive substances (NPS) account for 30% of all deaths in the United States. Since fentanyl derivatives and NPS are designed to produce similar effects, their related substances are similar or even have the same active groups. A comprehensive analysis of the related substances of alfentanil hydrochloride can provide a basis for the identification and supervision of fentanyl derivatives and NPS. METHODS: A liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (LC/QTOF-MS/MS) method was developed for the separation and characterization of related substances in alfentanil hydrochloride. Degradation studies were conducted according to the ICH-prescribed stress conditions. The compounds were identified mainly through positive electrospray ionization QTOF high-resolution mass spectrometric measurements of the accurate masses of the precursor and product ions and their calculated elemental compositions. Their formation mechanisms were also discussed. RESULTS: Seventeen related substances were detected in alfentanil hydrochloride and its stressed samples. Among them, nine were process-related substances and the other eight were degradation products. The stress study results demonstrated that alfentanil hydrochloride was unstable under acid, alkaline, and oxidative stress conditions, while relatively stable under dry photolytic and thermal stress conditions. Alfentanil hydrochloride was most susceptible for degradation at the N-phenylpropanamide and piperidine sites. CONCLUSIONS: Process-related alfentanil hydrochloride compounds are useful for determination of synthetic routes and entangling of fentanyl analogues. The stress study results can provide a sound scientific basis for the waste water monitoring of alfentanil. These results are important for routine quality control in the manufacturing and storage of alfentanil hydrochloride, as well as for drug enforcement of fentanyl and its analogues.

Population pharmacokinetics of ethanamizuril in normal and coccidiosis-infected chickens through ultra-performance liquid chromatography-Tandem Mass Spectrometry.

Ethanamizuril is a new triazine compound that shows potential for application in novel anticoccidial treatment. In this study, a pharmacokinetic model of ethanamizuril was established on the basis of the blood concentration of 81 experimental animals. The final model showed that ethanamizuril was distributed as a two-compartment model with first-order absorption after oral administration in chickens. Its clearance rate and volumn of central compartment distribution (Vc ) were affected by age and body weight, and volumn of central compartment distribution (Vc ) and volume of peripheral compartment distribution(Vp ) were influenced by weight and infection. External verification revealed that the model had good prediction accuracy and stability.

Preparation, evaluation and pharmacokinetics of diosmin herbosome in beagle dogs.

Diosmin is one of the most widely used phlebotonic drugs, but its poor bioavailability has restricted its usage. The aim of this study was to formulate a complex Diosmin with phospholipids (75% in PC, in 1:2 molar ratios) and to evaluate for solubility, drug content, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and in vitro dissolution study. Further to test the bioavailability of both the complex and Alvenor⌖ in beagle dogs and compare pharmacokinetic parameters. Diosmin herbosome was found to be more soluble than both pure diosmin and Alvenor⌖. The complex contained 71.94% drug content. DSC thermograms and XRD also proved the claim of the complexation. The dissolution profile of diosmin herbosome and Alvenor⌖ in water-ethanol medium showed an increase of the dissolution for diosmin herbosome. Comparison of plasma concentration and main pharmacokinetic parameters of diosmin herbosome treated and Alvenor⌖ treated dogs showed a higher Cmax for the complex with longer elimination half-life. The complexation of diosmin with phospholipids can be potentially used in enhancing the absorption and solubility, consequently increasing the bioavailability of the drug.

Separation and identification of process-related substances and degradation products in mycophenolate mofetil by liquid chromatography coupled with quadrupole-time of flight mass spectrometry.

Mycophenolate mofetil is an antiproliferative immunosuppressive agent. Since its clinical efficacy and safety highly depend on the quality, the stability, and impurity profiles of mycophenolate mofetil are paid ever-increasing attention. However, there are few published studies reporting the complete characterization of both the process-related substances and degradation products in mycophenolate mofetil. In the present study, a highly specific and efficient liquid chromatography coupled with quadrupole-time of flight mass spectrometry method was developed for the separation and identification of all the potential impurities in mycophenolate mofetil. According to the ICH Q1A (R2) guideline, the forced degradation studies were conducted to elucidate the stability and degradation pathways of mycophenolate mofetil. A total of 15 related substances, including the process-related substances and stress degradation products were characterized by the established hyphenated method, 11 of them have not been reported before. In view of the synthetic route and degradation pathways of mycophenolate mofetil, the origins and formation mechanisms of these related substances were discussed. Based on the obtained stability and impurity profiles, key points of the manufacturing process were proposed to deliver mycophenolate mofetil with high purity.

An LC-MS/MS method for quantification of HR011303, a novel highly selective urate transporter 1 inhibitor in beagle dogs and the application to a pharmacokinetic study.

HR011303 is a novel and highly selective urate transporter 1 (URAT1) inhibitor. In this study, a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for quantification of HR011303 in beagle dog plasma. Plasma samples were pretreated with protein-precipitation extraction by acetonitrile and added with a trifluoromethyl substituted analog of HR011303 as internal standard. The chromatographic separation was performed on a Shiseido C18 column (100 × 4.6 mm, i.d., 5 µm) by mobile phases consisting of 5 mm ammonium-formic acid (100:0.1) and acetonitrile-formic acid (100:0.1) solutions in gradient elution. The MS detection was conducted in electrospray positive ionization with multiple reactions monitoring at m/z 338 → 240 for HR011303 and m/z 328 → 230 for the internal standard using 25 eV argon gas collision induced dissociation. The established LC-MS/MS method showed good selectivity, sensitivity, precision and accuracy. The plasma pharmacokinetics of HR011303 in beagle dogs following both oral and intravenous administration were then successfully evaluated using this LC-MS/MS method.

Danggui Buxue Decoction Sensitizes the Response of Non-Small-Cell Lung Cancer to Gemcitabine via Regulating Deoxycytidine Kinase and P-glycoprotein.

This study aimed to investigate whether the anti-tumor effect of gemcitabine (GEM) in non-small-cell lung cancer (NSCLC) treatment was affected by Danggui Buxue decoction (DBD), and explore the potential mechanisms. The combined use of GEM and DBD showed an enhanced tumor growth inhibition effect in a murine Lewis lung carcinoma (LLC) model. LC-MS/MS results showed that the pharmacokinetic behaviors of a GEM active metabolite, gemcitabine triphosphate (dFdCTP), were found to be altered remarkably in the peripheral blood mononuclear cells (PBMC) of DBD co-administration rats. In addition, after co-administration of DBD with GEM, Western Blot and qPCR results confirmed that the expression of deoxycytidine kinase (dCK) in tumor tissues of LLC-bearing mice were markedly increased. DBD co-administration also reversed the upregulation of P-glycoprotein (P-gp) in tumor tissues induced by GEM. Moreover, DBD could notably up-regulate the IL-12p70 and GM-CSF expression in mice serum, suggesting potential immunomodulatory activities in tumor-bearing mice. Meanwhile, DBD inhibited the P-gp efflux activity in A549 cells. Therefore, the regulation of dCK and P-gp played important roles in the alternation of GEM pharmacokinetics and the enhancement of the anti-tumor effect of GEM. DBD being a potential dCK promoter could work as an adjuvant agent to boost the anticancer effect of GEM.

Profiling and Preparation of Metabolites from Pyragrel in Human Urine by Online Solid-Phase Extraction Coupled with High Performance Liquid Chromatography Tandem Mass Spectrometry Followed by a Macroporous Resin-Based Purification Approach.

Pyragrel, a new anticoagulant drug, is derived from the molecular combination of ligustrazine and ferulic acid. Pyragrel showed significant inhibitory activity against platelet aggregation induced by adenosine diphosphate (ADP), and had been approved for a phase I clinical trial by CFDA. To characterize the metabolites of Pyragrel in human urine after intravenous administration, a reliable online solid-phase extraction couple with high performance liquid chromatography tandem mass spectrometry (online SPE-HPLC-MSn) method was conceived and applied. Five metabolites were detected and tentatively identified, which suggested that the major metabolic pathways of Pyragrel in human were double-bond reduction, double-bond oxidation, and then followed by glucuronide conjugation. Two main metabolites were then prepared using ß-glucuronide hydrolysis and macroporous resin purification approach followed by preparative high-performance liquid chromatography (PHPLC) method, with their structures confirmed on the basis of nuclear magnetic resonance (NMR) data. This study provided information for the further study of the metabolism and excretion of Pyragrel.

[Pharmacokinetics of mercury after oral administration of cinnabaris and Fufang Niuhuang Xiaoyan capsule in rats].

Fufang Niuhuang Xiaoyan capsule was a classical compound prescription with the efficacy of heat-clearing, detoxification, sedation and anti-inflammation, with cinnabaris as one of its active ingredients. The study focuses on the pharmacokinetics of mercury in rats after oral administration of cinnabaris and Fufang Niuhuang Xiaoyan capsule, in order to explore the effect of combined traditional Chinese medicines on mercury metabolism. In this study, the method of nitric-perchloric acid digestion system coupled with cold atomic-atomic fluorescence spectroscopy (CV-AFS) was adopted to accurately determine mercury in whole blood of rats. Fufang Niuhueng Xiaoyan capsule had three dose schemes of oral administration, namely equivalent clinical dose, 3 times of equivalent clinical dose and 10 times of equivalent clinical dose; And the doses of oral administration of cinnabaris was calculated according to that of Fufang Niuhuang Xiaoyan capsule. SPF grade healthy SD rats were fasted overnight before the oral administration with cinnabaris suspension (or Fufang Niuhuang Xiaoyan capsule suspension). After oral administration of different doses of cinnabaris, no obvious changes in tmax and MRT were observed, while Cmax/dose, AUC0-48 h/dose and AUC0-∞/dose decreased with the increase in dose, indicating that total mercury absorption in body was declining. As the dose increased, Ke, CL/F decreased, and t1/2 increased, indicating that the elimination slowed down, and mercury metabolism showed non-linear dynamic characteristics within a certain range of dose (22-220 mg•kg⁻¹). The total mercury metabolism in the whole blood of rats after oral administration with different doses of Fufang Niuhuang Xiaoyan capsule also showed non-linear dynamic characteristics. The results were correlated with the low solubility of cinnabaris in the body. Compared with cinnabaris, Fufang Niuhuang Xiaoyan capsule showed no obvious changes in V/F and MRT, while Ke, CL/F, tmax decreased, and t1/2, Cmax/dose, AUC0-48 h/dose, AUC0-∞/dose increased significantly. The results showed that Fufang Niuhuang Xiaoyan capsule accelerated absorption, slowed down elimination and improved the total absorption of mercury in the whole blood, indicating that Fufang Niuhuang Xiaoyan capsule may contain components for promoting absorption and alleviating elimination of mercury. Fufang Niuhuang Xiaoyan capsule had an impact on the pharmacokinetics of cinnabaris, and long-term administration of cinnabaris (Fufang Niuhuang Xiaoyan capsule) was possible to cause accumulation of mercury in the body. This study could explain changes in efficacy of Fufang Niuhuang Xiaoyan capsule, evaluate the rationality of compound medicines containing toxic elements and provide scientific basis for the rational and safe use of Fufang Niuhuang Xiaoyan capsule.

A validated stability-indicating ultra performance liquid chromatography method for the determination of potential process-related impurities in eplerenone.

A simple, sensitive, and accurate stability-indicating analytical method has been developed and validated using ultra high performance liquid chromatography. The developed method is used to evaluate the related substances of eplerenone (EP). The degradation behavior of EP under stress conditions was determined, and the major degradants were identified by ultra high performance liquid chromatography with tandem mass spectrometry. The chromatographic conditions were optimized using an impurity-spiked solution, and the samples, generated from forced degradation studies. The resolution of EP, its potential impurities, and its degradation products was performed on a Waters UPLC BEH C18 column (50 × 2.1 mm, 1.7 µm) by linear gradient elution using a mobile phase consisting of 10 mmol/L ammonium acetate adjusted to pH 4.5, methanol and acetonitrile. A photo-diode array detector set at 245 nm was used for detection. The flow rate was set at 0.3 mL/min. The procedure had good specificity, linearity (0.02-3.14 µg/mL), recovery (96.1-103.9%), limit of detection (0.01-0.02 µg/mL), limit of quantitation (0.03-0.05 µg/mL), and robustness. The correction factors of the process-related substances were calculated.

Application of liquid chromatographic/tandem mass spectrometric method to a urinary excretion study of subutinib and active metabolite in human urine.

A novel and selective liquid chromatographic-mass spectrometric method (LC-MS/MS) has been established and validated for simultaneous determination of subutinib and active metabolite in human urine. Urine samples were extracted by liquid-liquid extraction with ethyl acetate and separated on a Wondasil C18 (150 × 2.1 mm, 3.5 µm), with methanol-0.2% formic acid solution (73:27, v/v) as mobile phase at flow rate of 0.2 mL/min. The linear range was 0.5000-200.0 ng/mL for subutinib and active metabolite, with a lower limit of quantitation of 0.5000 ng/mL. Intra- and inter-run precisions were all <11.8 and 14.3%, and the accuracies were all <4.5 and 5.4%, with the extraction recoveries 88.8-97.5 and 93.8-99.4% for the two analytes, respectively. The carryover values were all <15% for the two anayltes. The method was successfully applied to study urinary excretion of subutinib and active metabolite in human after oral administration of subutinib maleate capsules in fed and fasting states.

[Arsenic speciation in rat plasma after oral administration of realgar and Niu Huang Jie Du Pian].

The arsenic species in rat plasma were studied after oral administration of realgar and Niu Huang Jie Du Pian (NHJDP) and the possible compatible effects of realgar was evaluated by comparing the pharmacokinetics of arsenic species after administration of realgar and NHJDP. The separation of the arsenicals was performed by a high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) technique. Dimethylarsinic acid (DMA) was found to be the main species in rats' plasma after dosing. No traces of arsenite [As(Ⅲ)], monomethylarsonic acid (MMA) or arsenate [As(Ⅴ)] were detected at any sampling time points. Compared with realgar administration alone, dose-normalized peak concentration(C(max)) and AUC(0-t) of DMA were significantly decreased by NHJDP administration, while the t(max) was significantly delayed with the clearance and apparent volume of distribution significantly increased, indicating that the pharmacokinetics of As from realgar was affected by other ingredients in the compound prescription of NHJDP.

Discovery, stereospecific characterization and peripheral modification of 1-(pyrrolidin-1-ylmethyl)-2-[(6-chloro-3-oxo-indan)-formyl]-1,2,3,4-tetrahydroisoquinolines as novel selective κ opioid receptor agonists.

A novel series of 1-(pyrrolidin-1-ylmethyl)-2-[(3-oxo-indan)-formyl]-1,2,3,4-tetrahydroisoquinoline derivatives maj-3a-maj-3u were synthesized and evaluated in vitro for their binding affinity at κ-opioid receptors. Maj-3c displayed the highest affinity for κ-opioid receptors (Ki = 0.033 nM) among all the compounds evaluated. Furthermore, all four stereoisomers of compound 3c were prepared, and (1S,18S)-3c was identified as the most potent (Ki = 0.0059 nM) κ-opioid receptor agonist among the four stereoisomers. Maj-3c produced significant antinociception (ED50 = 0.000406 mg kg(-1)) compared to U-50,488H and original BRL 52580 in the acetic acid writhing assay, but its strong sedative effect (ED50 = 0.000568 mg kg(-1)) observed in the mouse rotation test reduced its druggability. To minimize the central nervous system side effects, a series of hydroxyl-containing analogs of maj-3c were synthesized, and maj-11a was found to be a potent κ-opioid receptor agonist (Ki = 35.13 nM). More importantly, the dose for the sedative effect (ED50 = 9.29 mg kg(-1)) of maj-11a was significantly higher than its analgesic dose (ED50 = 0.392 mg kg(-1)), which made it a promising peripheral analgesic candidate compound with weak sedative side effects.