Clickable Photoreactive ATP-Affinity Probe for Global Profiling of ATP-Binding Proteins.

Adenosine triphosphate (ATP) is the major energy carrier in organisms, and there are many cellular proteins that can bind to ATP. Among these proteins, kinases are key regulators in several cell signaling processes, and aberrant kinase signaling contributes to the development of many human diseases, including cancer. Hence, small-molecule kinase inhibitors have been successfully used for the treatment of various diseases. Since the ATP-binding pockets are similar for many kinases, it is very important to evaluate the selectivity of different kinase inhibitors. We report here a clickable ATP photoaffinity probe for the global profiling of ATP-binding proteins. After incubating the protein lysate with the ATP probe followed by ultraviolet (UV) irradiation, ATP-binding proteins were labeled with an alkyne handle for subsequent biotin conjugation through click chemistry. Labeled proteins were enriched with streptavidin beads, digested with trypsin, and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). More than 400 ATP-binding proteins, including approximately 200 kinases, could be identified in a single LC-MS/MS run in the data-dependent acquisition mode. We then applied this method to the analysis of targets of three selected ATP-competitive kinase inhibitors. We were able to successfully identify some of their reported target proteins from label-free quantification results and validated the results using Western blot analyses. Together, we developed a clickable ATP photoaffinity probe for proteome-wide profiling of ATP-binding proteins and demonstrated that this chemoproteomic method is amenable to high-throughput target identification of kinase inhibitors.

[Determination of trace genotoxic impurities in nifedipine by ultra high performance liquid chromatography-electrostatic field orbitrap high resolution mass spectrometry].

A method based on ultra high performance liquid chromatography-electrostatic field orbitrap high resolution mass spectrometry (UHPLC-Orbitrap HRMS) was established for the determination of genotoxic impurities 2, 6, and 12 in nifedipine. After extraction with methanol, the sample was injected into the UHPLC-Orbitrap HRMS system for analysis. An ACE EXCELTM 3 C18-AR column (150 mm×4.6 mm, 3 µm) was used for chromatographic separation. The mobile phase was methanol-0.1% formic acid aqueous solution (65∶35, v/v). The flow rate was 0.6 mL/min, while the column temperature and autosampler temperature were set as 35 ℃ and 8 ℃, respectively. The divert valve switching technique was used to protect the mass spectrometer. The six-way valve was set to divert the eluent of 7.5-11.6 min to waste and the rest of the eluent into the mass spectrometer. The Orbitrap mass spectrometer was coupled with the UHPLC system by an electrospray ion (ESI) source. The sheath gas and auxiliary gas flow rates were 60 and 20 arb (arbitrary units), respectively. The spray voltage was 3.5 kV, while the capillary temperature and auxiliary gas heater temperature were set as 350 ℃ and 400 ℃, respectively. The positive ion parallel reaction monitoring (PRM) scanning mode was adopted, and the mass spectral resolution was set to 35000 FWHM. The accurate masses of the [M+H]+ precursor ions of impurities 2, 6, and 12 were m/z 347.1230, 361.1026, and 347.1230, respectively. The accurate masses of the extracted [M+H]+ fragment ions of impurities 2, 6, and 12 were m/z 315.0968, 298.1069, and 315.0968, respectively. The normalized collision energies (NCEs) were optimized to 10%, 42%, and 10% for impurities 2, 6, and 12, respectively. The external standard method was utilized for quantitative analysis. The established method was validated in detail by investigating the specificity, linear range, limit of detection (LOD), limit of quantification (LOQ), recovery, precision, and stability. This method had good specificity, and the solvent did not interfere with the determination of impurities. The peak areas of impurities 2, 6, and 12 as well as their concentrations showed good linear relationships in the ranges of 0.2-100 ng/mL, with all correlation coefficients (r)≥0.9998. The recoveries of impurities 2, 6, and 12 at three levels (low, medium, and high) were in the range of 96.9%-105.0%, while the RSDs were between 1.21% and 5.12%. The LODs were 0.05 ng/mL and the LOQs were 0.2 ng/mL for all three impurities. This analytical method was used to determine impurities 2, 6, and 12 in three batches of nifedipine samples. Impurity 6 was not detected in the three batches, but impurities 2 and 12 were detected in all the three samples, and the detection amount was within the limit. The developed method is sensitive, fast, accurate, and easy to operate. It can provide a reference for the quality control of nifedipine by pharmaceutical companies and extend strong technical support for the supervision by drug regulatory authorities.

UHPLC-MS/MS method for pharmacokinetic and bioavailability determination of five bioactive components in raw and various processed products of Polygala tenuifolia in rat plasma.

CONTEXT: Sibiricose A5 (A5), sibiricose A6 (A6), 3,6'-disinapoyl sucrose (DSS), tenuifoliside A (TFSA) and 3,4,5-trimethoxycinnamic acid (TMCA) are the main active components of Polygala tenuifolia Willd. (Polygalaceae) (PT) that are active against Alzheimer's disease. OBJECTIVE: To compare the pharmacokinetics and bioavailability of five active components in the roots of raw PT (RPT), liquorice-boiled PT (LPT) and honey-stir-baked PT (HPT). MATERIALS AND METHODS: The median lethal dose (LD50) was evaluated through acute toxicity test. The pharmacokinetics of five components after oral administration of extracts of RPT, LPT, HPT (all equivalent to 1.9 g/kg of RPT extract for one dose) and 0.5% CMC-Na solution (control group) were investigated, respectively, in Sprague-Dawley rats (four groups, n = 6) using UHPLC-MS/MS. In addition, the absolute bioavailability of A5, A6, DSS, TFSA and TMCA after oral administration (7.40, 11.60, 16.00, 50.00 and 3.11 mg/kg, respectively) and intravenous injection (1/10 of the corresponding oral dose) in rats (n = 6) was studied. RESULTS: The LD50 of RPT, LPT and HPT was 7.79, 14.55 and 15.99 g/kg, respectively. AUC 0- t of RPT, LPT and HPT were as follows: A5 (433.18 ± 65.48, 680.40 ± 89.21, 552.02 ± 31.10 ng h/mL), A6 (314.55 ± 62.73, 545.76 ± 123.16, 570.06 ± 178.93 ng h/mL) and DSS (100.30 ± 62.44, 232.00 ± 66.08, 197.58 ± 57.37 ng h/mL). The absolute bioavailability of A5, A6, DSS, TFSA and TMCA was 3.25, 2.95, 2.36, 1.17 and 42.91%, respectively. DISCUSSION AND CONCLUSIONS: The pharmacokinetic and bioavailability parameters of each compound can facilitate future clinical studies.

Targeted and nontargeted screening and identification of 50 antihypertensive adulterants in dietary supplements and herbal medicines using quadrupole-orbitrap high resolution mass spectrometry with compound database.

In the present work, a novel database of drug compounds and a rapid screening method based on ultra-high performance liquid chromatography coupled to high resolution orbitrap mass spectrometry were developed and applied in the screening and identification of targeted and nontargeted antihypertensive adulterants in dietary supplements and herbal medicines. The established screening database includes retention time, exact mass, fragments, isotopic pattern, and MS2 spectra library of the target compounds and thus provides automated search and identification of the targets with a single injection. The nontargeted compounds in the samples are identified through the full MS scan and MS2 data by using the Chemspider database and the data analysis in XCalibur, MassFrontier and TraceFinder software. In addition, this method possesses excellent quantitative capacity. The novel approach was applied to 65 batches of samples that are claimed as "all-natural" products having the antihypertensive function, among which nine batches were found to be positive. Multiple targeted and nontargeted antihypertensive adulterants were detected at levels ranging from 2.8 to 27.9 mg/g. The novel database and screening method demonstrated herein will be promising and powerful tools for rapid screening of antihypertensive adulterants in dietary supplements and herbal medicines.

[Determination of N-nitrosodimethylamine in metformin hydrochloride and its preparations by high performance liquid chromatography-tandem mass spectrometry].

A method was established for the determination of N-nitrosodimethylamine (NDMA) in metformin hydrochloride active pharmaceutical ingredient (API) and preparation samples by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Water was used as the extraction solvent for the metformin hydrochloride API and preparation samples. The samples were analyzed by HPLC-MS/MS after vortex mixing, constant temperature shaking, high speed centrifugation and microfiltration. An ACE EXCEL 3 C18-AR column (150 mm×4.6 mm, 3 µm) was used for chromatographic separation. The mobile phases were water and methanol both containing 0.1% formic acid with gradient elution. The flow rate, column temperature, and autosampler temperature were set as 0.8 mL/min, 40℃, and 10℃, respectively. The valve switching technique was used to protect the mass spectrometer, while six-way valve switching was adopted to allow the mobile phase with a retention time of 2.85-7.00 min to enter the mass spectrometer and the mobile phase with other retention times to enter the waste liquid. For the mass spectrometer, an atmospheric pressure chemical ionization (APCI) ion source was used in positive ion MRM scanning mode. The other conditions were as follows:atomizer flow, 3 L/min; heater flow, 10 L/min, interface temperature, 300℃; desolvation line (DL) temperature, 250℃; heating block temperature, 400℃; and dryer flow, 10 L/min. The quantitative transition of NDMA was m/z 75.0→43.1 with a collision energy of-17.0 eV, while the qualitative transition was m/z 75.0→58.2 with a collision energy of-16.0 eV. The external standard method was utilized for quantitative analysis. The established method was validated in detail by investigating the specificity, linear range, limit of detection, limit of quantification, recovery, precision, and stability. This method showed good specificity, since the solvents and excipients did not interfere with the determination of NDMA. A good linear relationship was observed the NDMA peak area and the mass concentrations in the range of 1.00-100.00 ng/mL with an excellent correlation coefficient (r>0.9999). The limit of detection and limit of quantification in solution were 0.20 ng/mL and 1.00 ng/mL, respectively. The recoveries of NDMA at low, medium, and high spiked levels ranged from 94.55% to 114.67%, and the RSDs ranged from 4.73% to 13.46%, indicating good accuracy and precision for the quantification of NDMA. Stability tests showed that NDMA was stable when placed in the autosampler for 0, 8, 24 h, since the RSD of the peak area was as low as 2.08%. The validated method was then applied to the determination of NDMA in metformin hydrochloride raw materials and preparations (tablets, capsules or enteric tablets). The detected amount of NDMA in the API did not exceed the limit in 113 batches of samples, but NDMA was detected and exceeded the limit in eight batches of preparations. This method is sensitive, accurate, and easy to operate, and it can be used for the determination of NDMA in metformin hydrochloride raw materials and preparation samples.

[Application of Orbitrap high resolution mass spectrometry for the screening and identification of 15 adulterated weight loss compounds in dietary supplements].

A liquid chromatography-Orbitrap high resolution mass spectrometry (LC-HRMS) method and a TraceFinder database were developed for the screening and identification of 15 adulterated weight loss compounds in dietary supplements. The samples were extracted with methanol and filtered through a 0.22 µm microfiltration membrane prior to LC-HRMS analysis. The Full MS/dd-MS2 mode was utilized in both positive and negative ion modes and the collected data were imported into the TraceFinder screening software. The established compound database and screening method were used for rapid, automatic, and high-precision screening to determine if the weight loss compounds were adulterated. The method validation results indicated that all of the analytes showed excellent linear relationships with regression coefficients (r) above 0.998. The recoveries were in the range of 79.7%-95.4% while the precisions ranged from 3.3% to 8.7%. The method and database were used to screen weight loss adulterants in 29 batches of dietary supplements; six batches of samples tested positive for adulterants with the identification of four compounds including sibutramine. This method enables the automatic high-precision screening and identification of adulterants, providing a novel and powerful tool for combating the increasingly rampant occurrence of adulteration in dietary supplements.

Application of quadrupole-Orbitrap high-resolution mass spectrometry in rapid screening and identification of synthetic dyes in herbal medicines.

In this work, a method combining ultra-high performance liquid chromatography and hybrid quadrupole-Orbitrap high-resolution mass spectrometry (HR-MS) was developed and validated for use in the simultaneous screening, identification, and quantification of 21 synthetic dyes in herbal medicines. To optimize the chromatographic conditions, we used a combined Full mass scan and data-dependent MS/MS (Full MS/dd-MS2) approach in positive and negative ion mode. Under this mode, selected ions with given fragmentation energy were subjected to a dd-MS2 scan following a Full MS scan. The selectivity of this method was effectively improved using 70,000 full width at half maximum mass resolution and narrow mass window (typically 5 ppm), and a single injection was sufficient for simultaneous identification and quantification of 21 synthetic dyes within 10 min. The combined method was fully validated and complies with all criteria for selectivity, sensitivity, calibration curve linearity, accuracy, precision, recovery, matrix effect, and stability. All analytes showed excellent linear relationships as all the coefficients of determination (r2) are greater than 0.9978 over wide ranges of concentrations (e.g. 1.0-500 ng/mL for sunset yellow). The validated method was employed to detect synthetic dyes in herbal medicines and was demonstrated to provide a reliable technical basis for drug regulation and public health protection.

[Determination of ambroxol hydrochloride in human plasma by ultra high performance liquid chromatography-tandem mass spectrometry and bioequivalence evaluation of its preparation].

A rapid, simple and sensitive ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for the determination of ambroxol hydrochloride in human plasma, and bioequivalence of its preparation was evaluated. The 50 µL-plasma sample was treated with methanol for protein precipitation, while ambroxol-d5 was used as an internal standard (IS). The separation was carried out on a Waters XBridge BEH C18 column (50 mm×2.1 mm, 2.5 µm) by gradient elution at a flow rate of 0.4 mL/min, with 0.1% (v/v) formic acid aqueous solution and methanol containing 0.1% (v/v) formic acid as the mobile phases. The analyte was detected using an electrospray ionization source in positive ion multiple reaction monitoring (MRM) mode. The calibration curves were linear in the range of 2-400 ng/mL (r=0.998). The intra- and inter-run accuracies were 97.1%-108.7%, the intra- and inter-run precisions were 1.0%-5.6%. The method was applied to the determination of the plasma concentration of the six healthy subjects after the oral administration of 30 mg of test and reference preparations. The bioavailability was (102.3±14.8)%. The 90% confidence intervals of the test preparation's pharmacokinetic parameters were 80.0%-125.0% of the reference preparation's corresponding parameters. Thus, it is proved that the test preparation and reference preparation are bioequivalent.

Application of an ultrahigh-performance liquid chromatography coupled to quadrupole-orbitrap high-resolution mass spectrometry for the rapid screening, identification and quantification of illegal adulterated glucocorticoids in herbal medicines.

In this work, the ultrahigh-performance liquid chromatography quadrupole orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) was applied to the rapid screening, identification and quantification of the illegal adulterated glucocorticoids in herbal medicines. The mass spectrometer was operated in positive ion mode and Full MS/dd-MS2 (data-dependent MS2) mode, where selected ions were subjected to a dd-MS2 scan with given fragmentation energy following a Full MS scan. The application of 70 000 FWHM mass resolution and narrow mass windows (5ppm) effectively improve the selectivity of the method, and a single injection was sufficient to perform the simultaneous screening and identification/quantification of 14 glucocorticoids in 15min. The method validation including selectivity, sensitivity, calibration curve, accuracy, precision, recovery, matrix effect and stability were evaluated. The results of all analytes showed excellent linear relationship while all coefficient of determination (r2) were>0.9990 over wide concentration ranges (e.g., 5-1000ng/mL for hydrocortisone butyrate, r2=1.0000). The recoveries were in the range of 86.1-102.7%, while the matrix effects ranged from 95.8%-105.8%. Accuracies and precisions were performed. The intra- and inter-day accuracies ranged from 90.6% to 108.9%, while the intra- and inter-day precisions were in the range of 0.5% to 8.5%. Finally, the established method was employed to detect illegal adulterated glucocorticoids in herbal medicines. It will provide more reliable technical basis for the drug quality supervision department and ensure public health.

[Determination of nine pesticide residues in vegetables by matrix solid-phase dispersion-ultra performance liquid chromatography-tandem mass spectrometry].

A matrix solid-phase dispersion-ultra performance liquid chromatography-tandem mass spectrometry (MSPD-UPLC-MS/MS) method was established for the simultaneous deter- mination of carbendiazin, omethoate, carbofuran, aldicarb, chlorpyrifos, methamidophos, phorate, parathion and parathion-methyl residues in vegetables. The samples were extracted by acetonitrile and separated with salting out method. And then the supernatants were purified by matrix solid-phase dispersion for the UPLC-MS/MS analysis. The separation was performed on a Waters Acquity UPLC system with a BEH C18 column with the gradient elution of acetonitrile and water containing 0. 1% (v/v) acetic acid. The nine pesticides were determined in the modes of electrospray positive ionization (ESI+) and multiple reaction monitoring (MRM). The ana- lytes were quantified by matrix matched standard solution curves. The limits of detection (S/N ≥ 3) were 0.8-4.0 µg/kg. The average recoveries were 72.8%-117.4%. The detection rates were 42.0% for chlorpyrifos, 14.0% for carbendiazin and 1.5% for dimethoate, and the exces- sive rate of chlorpyrifos was 8.0% in the determination of 50 real samples; the other pesticides were not detected. The method is simple, accurate and highly reproducible. This method is suit- able for the quality control of pesticide residues in risk monitoring of the safety of the foods.

Development of an ultra-high-performance liquid chromatography coupled to high-resolution quadrupole-Orbitrap mass spectrometry method for the rapid detection and confirmation of illegal adulterated sedative-hypnotics in dietary supplements.

A novel method using ultra-high performance liquid chromatography coupled to hybrid quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap) was developed and validated for the simultaneous screening, identification and quantification of sedative-hypnotics in dietary supplements. Chromatographic conditions were optimised and a full data-dependent MS(2) scan (MS/dd-MS(2)) in positive and negative ion mode was used. A single injection was sufficient to perform the simultaneous screening and identification/quantification of samples. The response showed a good linear relationship with analyte concentrations over wide ranges (e.g., 1.0-1000 ng g(-1) for diazepam) with all the determination coefficients (r(2)) > 0.9985. The method was validated, obtaining accuracy (intra- and inter-day) in the range of 94.5-105.3% and precision (intra- and inter-day) in the range of 0.4-8.9%, respectively. The detection limits (LODs) were in the range of 0.3-1.0 ng g(-1) for different analytes. Recoveries were performed and ranged from 74.1% to 90.2%, while all matrix effects were over the range of 85.4-93.6%. Finally, this method was used to detect sedative-hypnotics in commercial dietary supplements. Of a total of 45 batches of dietary supplements, only three batches were found to be positive samples with concentrations of diazepam, clonazepam and alprazolam at high levels (≥ 8.22 mg g(-1)).

Ultra-trace analysis of 12 ß2-agonists in pork, beef, mutton and chicken by ultrahigh-performance liquid-chromatography-quadrupole-orbitrap tandem mass spectrometry.

This paper presents an application of ultrahigh-performance liquid-chromatography - quadrupole - orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) for the ultra-trace analysis of 12 ß2-agonists in pork, beef, mutton and chicken meat. The mass spectrometer was operated in Full MS/dd-MS(2) (data-dependent MS(2)) mode, under which a Full MS scan was followed by a dd-MS(2) scan with a fragmentation energy. The quantification was achieved using matrix-matched standard calibration curves with salbutamol-d3 and clenbuterol-d9 as the internal standards. The method validation included assessment of selectivity, sensitivity, calibration curve, accuracy, precision, recovery, matrix effect and stability. The results show an exceptional linear relationship with the concentrations of the analytes over wide concentration ranges (e.g., 0.01-50 µg/kg for clenbuterol) as all the fitting coefficients of determination r(2) are >0.9986. The detection limits (LODs) were in the range of 0.0033-0.01 µg/kg, which was much lower than the current reported methods. The recoveries were able to reach 73.0-88.7%, while the matrix effects ranged from 83.7% to 92.8%. Analysis of 400 pork, beef, mutton and chicken samples reveal that only 4.25% samples were positive for ß2-agonists. The detected ß2-agonists involved salbutamol, clenbuterol, ractopamine and clorprenaline. Overall, the novel Q-Orbitrap technique was demonstrated to have great performance for the screening, identification and quantification of ultra-trace ß2-agonists used in food animal muscles, which helps to ensure food safety and public health.

Simultaneous identification, confirmation and quantitation of illegal adulterated antidiabetics in herbal medicines and dietary supplements using high-resolution benchtop quadrupole-Orbitrap mass spectrometry.

This paper presents an application of ultrahigh-performance liquid chromatography and quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HR MS) for the screening, confirmation and quantification of 11 antidiabetics in herbal medicines and dietary supplements. The mass spectrometer was operated in Full MS/dd-MS(2) (data-dependent MS(2)) mode. The full MS scan acquired data for identification and quantification, and dd-MS(2) scan obtained product ion spectra for confirmation. UHPLC-Q-Orbitrap MS quantification was achieved using matrix-matched standard calibration curves with phenacetin as internal standard. The method validation that included selectivity, sensitivity, calibration curve, accuracy and precision, recovery, matrix effect and stability was evaluated. The response showed good linear relationship with the concentrations of analytes over wide ranges (e.g., 0.0004-1 µg/g for metformin) with all the coefficients of correlation (r(2)) >0.9991. The detection limits (LODs) were in the range of 0.05-0.5 ng/g for different analytes. The recoveries yielded results higher than 74.3% for all compounds. The accuracy was in the range of -6.75 to 3.85%, while the intra- and inter-day precision ranged from 0.048 to 11.5%. Among 63 batches of herbal medicines and 34 batches of dietary supplements samples, 7 batches of dietary supplements were positive, while all the herbal medicines were negative. Overall, the novel UHPLC-Q-Orbitrap has demonstrated great performance for identification, confirmation and quantification of antidiabetics in herbal medicines and dietary supplements, ensuring food safety and public health.

Application of a high resolution benchtop quadrupole-Orbitrap mass spectrometry for the rapid screening, confirmation and quantification of illegal adulterated phosphodiesterase-5 inhibitors in herbal medicines and dietary supplements.

In this study, the applicability of high resolution quadrupole-Orbitrap (Q-Orbitrap) mass spectrometry for the simultaneous qualitative and quantitative analysis of illegal adulterated phosphodiesterase-5 inhibitors (PDE-5 inhibitors) in herbal medicines and dietary supplements was investigated. The mass spectrometer was operated in full MS scan/dd-MS(2) (data-dependent MS(2)) mode. The use of 70,000 FWHM mass resolution and narrow mass windows (5 ppm) could effectively improve the selectivity of the method, increasing the signal-to-noise ratio for the analytes. The response showed good linear relationship with the analytes' concentrations over wide ranges (e.g., 0.05-10 µg/g for sildenafil) with all the coefficient of determinations (r(2)) >0.9996. The detection limits (LODs) were in the range of 1.0-5.0 ng/g for different analytes. The recoveries ranged from 85.4% to 96.7%. The intra- and inter-day accuracies were in the range of -6.6 to 10.1%, while the intra- and inter-day precision ranged from 0.0039% to 13.2%. Among 68 batches of herbal medicines and 20 batches of dietary supplements (including 83 capsules, 3 pellets and 2 liquid) samples, sildenafil was detected in 8 dietary supplements, while noracetildenafil was detected in only one dietary supplement. The novel Q-Orbitrap mass spectrometry has been proved to be a very promising and powerful tool for routine screening of illegal adulterate in herbal medicines and dietary supplements, ensuring food safety and public health.

Application of a liquid chromatography-tandem mass spectrometry method to the pharmacokinetics, tissue distribution and excretion studies of Dactylicapnos scandens in rats.

The herbal ingredients of isocorydine and protopine were isolated from Dactylicapnos scandens. This study was aimed at developing a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method to quantify isocorydine and protopine in rat plasma and tissues for pharmacokinetic, tissue distribution and excretion studies. Biological samples were processed with ethyl acetate extraction, and corydaline was chosen as the internal standard (IS). The analytes were separated by a C(18) column and detected with a triple quadrupole mass spectrometer using positive ion ESI in the multiple reaction monitoring (MRM) mode. The MS/MS ion transitions monitored were m/z 342.0→278.9 for isocorydine, 354.1→188.0 for protopine and 370.0→192.0 for IS, respectively. Excellent linearity was observed over the concentration range between 10 and 3000 ng/mL for isocorydine and 10-300 ng/mL for protopine. The lower limit of quantification (LLOQ) was 10 ng/mL for both isocorydine and protopine. This novel method was rapid, accurate, high sensitive and high selective. It was successfully applied to the pharmacokinetic, tissue distribution and excretion studies of D. scandens. These preclinical data of D. scandens would be useful for the clinical reference.

Rapid determination of isocorydine in rat plasma and tissues using liquid chromatography--tandem mass spectrometry and its applications to pharmacokinetics and tissue distribution.

A rapid and sensitive method for the determination of isocorydine in rat plasma and tissues was developed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biological samples were processed by extracting with diethyl ether-dichloromethane (3:2, v/v) and tetrahydropulmatine was used as the internal standard (IS). Detection of the analytes was achieved using positive ion mode electrospray ionization in the multiple reaction monitoring mode. The MS/MS ion transitions monitored were m/z 342.0→279.0 and 356.0→191.9 for isocorydine and IS, respectively. The maximum plasma concentration (C(max) 2496.8 ± 374.4 µg/L) was achieved at 0.278 ± 0.113 h (T(max)) and the half-life (t(1/2)) of isocorydine was 0.906 ± 0.222 h after a 20 mg/kg oral administration. As for a 2 mg/kg intravenous (i.v.) administration, the C(max) and clearance (CL) were 1843.3 ± 338.3 µg/L and 2.381 ± 0.356 L/h/kg, respectively. Based on the AUC(0-∞) obtained from oral and i.v. administration, the absolute bioavailability (F) was estimated as 33.4%. Tissue distribution results indicated that isocorydine underwent a rapid and wide distribution into tissues and it could effectively cross the blood-brain barrier.

Fluorescence determination of DNA using the gatifloxacin-europium(III) complex.

A method for the determination of DNA based on the fluorescence intensity of the gatifloxacin-europium(III) (GFLX-Eu(3+)) complex that could be enhanced by DNA was developed. The GFLX-Eu(3+) complex showed an up to 6-fold enhancement of luminescence intensity after adding DNA. Under the optimized experimental conditions, the system exhibited a linear relationship between the enhanced fluorescence intensity and the concentration of calf thymus DNA (ctDNA) over the range from 1.0 × 10(-8) to 1.5 × 10(-6) g mL(-1), with a correlation coefficient (R) of 0.997, and the detection limit (3σ) of the method was determined as 6.0 × 10(-9) g mL(-1). The mechanism of the fluorescence enhancement effect was also discussed.

Analysis of chiral non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac binding with HSA.

The protein binding of non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac with human serum albumin (HSA) was investigated using indirect chiral high performance liquid chromatography (HPLC) and ultrafiltration techniques. S-(-)-1-(1-naphthyl)-ethylamine (S-NEA) was utilized as chiral derivatization reagent and pre-column derivatization RP-HPLC method was established for the separation and assay of the three pairs of enantiomer. The method had good linear relationship over the investigated concentration range without interference. The average extraction efficiency was higher than 85% in different systems, and the intra-day and inter-day precisions were less than 15%. In serum albumin, the protein binding of etodolac enantiomers showed significant stereoselectivity that the affinity of S-enantiomer was stronger than R-enantiomer, and the stereoselectivity ratio reached 6.06; Flurbiprofen had only weak stereoselectivity in HSA, and ketoprofen had no stereoselectivity at all. Scatchard curves showed that all the three chiral drugs had two types of binding sites in HSA.

Development of high performance liquid chromatography/electrospray ionization mass spectrometry for assay of ginkgolic acid (15:1) in rat plasma and its application to pharmacokinetics study.

A highly sensitive HPLC-ESI-MS method has been developed and validated for the quantification of ginkgolic acid (15:1) in a small quantity of rat plasma (50µL) using its homologous compound ginkgolic acid (17:1) as an internal standard. GA (15:1) and GA (17:1) were extracted from biological matrix by direct protein precipitation with 5-fold volume of methanol and separated on an Elite hypersil BDS C(18) column (2.1×100mm, 3µm), eluted with acetonitrile:water (92:8, v/v, containing 0.3% glacial acetic acid). Linear range was 8-1000ng/mL with the square regression coefficient (r(2)) of 0.996. The lowest concentration (8ng/mL) in the calibration curve was estimated as LLOQ with both deviation of accuracy and RSD of precision <20% (n=6). The intra- and inter-day precision ranged from 3.6% to 9.9%, and the intra- and inter-day accuracy was between 89.9% and 101.3%. This method was successfully applied to study pharmacokinetics of GA (15:1) in rats after oral administration at a dose of 10mg/kg. GA (15:1) pharmacokinetic parameters C(max), T(max), t(1/2), AUC(0-12h) are 1552.9±241.0ng/mL, 0.9±0.7h, 5.5±2.6h, 3356.0±795.3ngh/mL, respectively.