Showing papers in "Biomedical Chromatography in 2013"

Rapid screening and identification of α-glucosidase inhibitors from mulberry leaves using enzyme-immobilized magnetic beads coupled with HPLC/MS and NMR

Abstract: α-Glucosidase plays important roles in the digestion and absorption of carbohydrates in the small intestine. The inhibition of α-glucosidase is regarded as a potential way to treat diabetes. We established an approach to screening α-glucosidase inhibitors from medicinal plants using enzyme-coated magnetic bead. Using 1-(3-dimethyl-aminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide as reaction reagents, α-glucosidase was immobilized on the magnetic beads by covalent linkage. The conjugation of α-glucosidase to the magnetic beads was characterized using scanning electron microscope and X-ray diffractometer. The proposed approach was applied in fishing potential α-glucosidase inhibitors from extract of Morus alba, a Chinese medicinal plant. The structures of potential active compounds were identified via liquid chromatography–mass spectrometry and nuclear magnetic resonance. The results demonstrated that two flavonoids (isoquercitrin and astragalin) could bind to α-glucosidase, which was confirmed via conventional α-glucosidase inhibitory assay. Our findings suggested that enzyme-coated magnetic beads may be suitable for discovering active compounds from medicinal plants. Copyright © 2012 John Wiley & Sons, Ltd.

Method development and validation for the quantification of dasatinib, erlotinib, gefitinib, imatinib, lapatinib, nilotinib, sorafenib and sunitinib in human plasma by liquid chromatography coupled with tandem mass spectrometry.

Abstract: To support pharmacokinetic-guided dosing in individual patients, a fast and accurate method for simultaneous determination of anticancer tyrosine kinase inhibitors (TKIs) dasatinib, erlotinib, gefitinib, imatinib, lapatinib, nilotinib, sorafenib and sunitinib in human plasma was developed using high-performance liquid chromatography and detection with tandem mass spectrometry (HPLC-MS/MS). Stable isotopically labeled compounds of the eight different TKIs were used as internal standards. Plasma proteins were precipitated and an aliquot of supernatant was directly injected onto a reversed phase chromatography system consisting of a Gemini C18 column (50 x 2.0 mm i.d., 5.0 microm particle size) and then compounds were eluted with a gradient. The outlet of the column was connected to a triple quadrupole mass spectrometer with electrospray interface. Ions were detected in the positive multiple reaction monitoring mode. This method was validated over a linear range from 20.0 to 10,000 ng/mL for erlotinib, gefitinib, imatinib, lapatinib, nilotinib and sorafenib, and from 5.00 to 2500 ng/mL for dasatinib and sunitinib. Results from the validation study demonstrated good intra- and inter-assay accuracy (<13.1%) and precision (10.0%) for all analytes. This method was successfully applied for routine therapeutic drug monitoring purposes in patients treated with the investigated TKIs. Copyright (c) 2012 John Wiley & Sons, Ltd.

LC-MS/MS method for simultaneous analysis of uracil, 5,6-dihydrouracil, 5-fluorouracil and 5-fluoro-5,6-dihydrouracil in human plasma for therapeutic drug monitoring and toxicity prediction in cancer patients

Abstract: The chemotherapeutic drug 5-fluorouracil (5-FU) is widely used for treating solid tumors. Response to 5-FU treatment is variable with 10-30% of patients experiencing serious toxicity partly explained by reduced activity of dihydropyrimidine dehydrogenase (DPD). DPD converts endogenous uracil (U) into 5,6-dihydrouracil (UH(2) ), and analogously, 5-FU into 5-fluoro-5,6-dihydrouracil (5-FUH(2) ). Combined quantification of U and UH(2) with 5-FU and 5-FUH(2) may provide a pre-therapeutic assessment of DPD activity and further guide drug dosing during therapy. Here, we report the development of a liquid chromatography-tandem mass spectrometry assay for simultaneous quantification of U, UH(2) , 5-FU and 5-FUH(2) in human plasma. Samples were prepared by liquid-liquid extraction with 10:1 ethyl acetate-2-propanol (v/v). The evaporated samples were reconstituted in 0.1% formic acid and 10 μL aliquots were injected into the HPLC system. Analyte separation was achieved on an Atlantis dC(18) column with a mobile phase consisting of 1.0 mm ammonium acetate, 0.5 mm formic acid and 3.3% methanol. Positively ionized analytes were detected by multiple reaction monitoring. The analytical response was linear in the range 0.01-10 μm for U, 0.1-10 μm for UH(2) , 0.1-75 μm for 5-FU and 0.75-75 μm for 5-FUH(2) , covering the expected concentration ranges in plasma. The method was validated following the FDA guidelines and applied to clinical samples obtained from ten 5-FU-treated colorectal cancer patients. The present method merges the analysis of 5-FU pharmacokinetics and DPD activity into a single assay representing a valuable tool to improve the efficacy and safety of 5-FU-based chemotherapy.

Molecularly imprinted polymer in microextraction by packed sorbent for the simultaneous determination of local anesthetics : lidocaine, ropivacaine, mepivacaine and bupivacaine in plasma and urine samples

Abstract: This study presents the use of molecularly imprinted polymer (MIP) as packing material for microextraction by packed syringe (MEPS) to achieve higher extraction selectivity. Pentycaine was used as template for MIP. Development and validation of the determination of lidocaine, ropivacaine, mepivacaine and bupivacaine in human plasma and urine samples utilizing MIP-MEPS and liquid chromatography–tandem mass spectrometry (LC-MS/MS) were carried out. The MEPS MIP-cartridge could be used for 100 extractions before it was discarded. The extraction recovery ranged from 60 to 80%. The correlation coefficients values were >0.999 for all assays using lidocaine, ropivacaine, mepivacaine and bupivacaine in the calibration range 5–2000 nmol/L. The accuracy of the studied compounds, given as a percentage variation from the nominal concentration values, ranged from -4.9 to 8.4% using plasma and urine samples. The between-batch precision, given as the relative standard deviation, at three different concentrations (quality control samples) was ranged from −4.7 to 14.0% and from 1.8 to 12.7% in plasma and urine, respectively. The lower limit of quantification and limit of detection of the studied substances were 5.0 and 1.0 nm, respectively

Profiling and identification of the absorbed constituents and metabolites of schisandra lignans by ultra-performance liquid chromatography coupled to mass spectrometry.

Abstract: Schisandra chinensis Baill grows wild in Russia, China, Korea and Japan, and its fruit has been found to be effective in amnesia and insomnia. It is enriched in schisandra lignans (SL) that are major components responsible for therapeutic action. However, there are no reports on the biotransformation analysis of SL. An ultra-performance liquid chromatography/electrospray-ionization high-definition mass spectrometry (UPLC-Q-TOF-HDMS) method was developed to investigate the metabolism of SL in vivo. MS was performed on a Waters Micromass high-definition system with an electrospray ionization source in positive ion mode and automated MetaboLynx software analysis with excellent MS accuracy and enhanced MS data acquisition. An improved mass defect filter (MDF) method employing both drug and core structure filter templates was applied to the processing of UPLC-Q-TOF-HDMS data for the detection and structural characterization of metabolites. In this study, 30 metabolites were detected and identified in vivo, and demethylation and hydroxylation were confirmed as the primacy metabolic pathway for SL in rat plasma. In conclusion, the presently developed methodology was suitable for biotransformation research of SL and will find wide use in metabolic studies for other herbal medicines. Copyright © 2013 John Wiley & Sons, Ltd.

Characterization of in vivo antioxidant constituents and dual-standard quality assessment of Danhong injection.

Abstract: Antioxidants and oxidative stress play a critical role in cardiovascular diseases. Danhong injection (DHI) is a well prescribed cardiovascular medication in China, but its detailed chemical basis and mechanisms of action remain unknown. To prove the antioxidant activity of DHI, its free radical scavenging capacity (RSC) was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) spectrophotometric assay. The 50% radical scavenging activity value was 1:129.2 mL/mL, against 0.95 mM DPPH. To further identify the antioxidant compounds, modified thin-layer chromatography combined with DPPH bioautography assay was used. Compared with vitamin C, 11 of 16 available compounds displayed strong antioxidant activity, which were also detected in rat serum after intravenous administration of DHI by ultra-performance liquid chromatography-tandem mass spectrometry, except for hydroxysafflor yellow A. Therefore, 10 antioxidants remaining in the blood as key markers, and six other compounds as general markers, were employed to perform the quality control of DHI by ultra-performance liquid chromatography-ultraviolet detection after systematic methodological validation. The analytical results indicate a high correlation (r = 0.9) between the total content of those antioxidants remaining in blood and RSC of DHI among 10 batches. Further, the antioxidant profiling and chemical marker quantification as dual-standard quality assessment was successfully applied to evaluate Danshen and safflower injections.

LC/MS/MS analysis of the endogenous dimethyltryptamine hallucinogens, their precursors, and major metabolites in rat pineal gland microdialysate

Abstract: We report a qualitative liquid chromatography–tandem mass spectrometry (LC/MS/MS) method for the simultaneous analysis of the three known N,N-dimethyltryptamine endogenous hallucinogens, their precursors and metabolites, as well as melatonin and its metabolic precursors. The method was characterized using artificial cerebrospinal fluid (aCSF) as the matrix and was subsequently applied to the analysis of rat brain pineal gland-aCSF microdialysate. The method describes the simultaneous analysis of 23 chemically diverse compounds plus a deuterated internal standard by direct injection, requiring no dilution or extraction of the samples. The results demonstrate that this is a simple, sensitive, specific and direct approach to the qualitative analysis of these compounds in this matrix. The protocol also employs stringent MS confirmatory criteria for the detection and confirmation of the compounds examined, including exact mass measurements. The excellent limits of detection and broad scope make it a valuable research tool for examining the endogenous hallucinogen pathways in the central nervous system. We report here, for the first time, the presence of N,N-dimethyltryptamine in pineal gland microdialysate obtained from the rat. Copyright © 2013 John Wiley & Sons, Ltd.

High-performance liquid chromatography tandem mass spectrometry method for the determination of 2CC-NBOMe and 25I-NBOMe in human serum.

Abstract: 2CC-NBOMe {4-chloro-2,5-dimethoxyphenethyl-N-[(2-methoxyphenyl) methyl] ethanamine} and 25I-NBOMe {2-(4-iodo-2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl) methyl] ethanamine} are of a class of N-benzyl phenethylamine derivatives whose synthesis was first reported in the scientific literature in 2011 Recent reports from 'personal drug experience websites' and in the popular press indicate these drugs are the latest in a series of designer 'Bath Salt' drugs of abuse The presented high-performance liquid chromatography triple quadrupole mass spectrometry (HPLC/MS/MS) method was developed for the detection and quantification of 2CC-NBOMe and 25I-NBOMe in serum of intoxicated emergency department patients The assay applies 2-​(2,​5-​dimethoxyphenyl)-​N-​(2-​methoxybenzyl) ethanamine (25H-NBOMe) as the internal standard Samples were extracted using solid-phase extraction columns The chromatographic separation was performed on a Luna 3 µ C8(2) 100 A, 100 × 20 mm, column Detection was accomplished by multiple-reaction monitoring via an electrospray ionization source operating in the positive ionization mode The calibration curves were linear over the investigated concentration range, 30-2000 pg/mL, with a lower limit of detection of 10 pg/mL for both 2CC-NBOMe and 25I-NBOMe The method proved suitable for serum clinical toxicology testing Two severely intoxicated emergency department patients were determined to have serum concentrations of 250 and 2780 pg/mL of 25I-NBOMe using the presented method

Simultaneous quantitative analyses of indole and oxindole alkaloids of Uncaria Hook in rat plasma and brain after oral administration of the traditional Japanese medicine Yokukansan using high-performance liquid chromatography with tandem mass spectrometry

Abstract: Uncaria Hook (UH) alkaloids are involved in the beneficial effects of Yokukansan. However, the pharmacokinetics of UH alkaloids after oral administration of Yokukansan has not yet been sufficiently investigated. Therefore, we developed and validated a sensitive and specific high-performance liquid chromatography with tandem mass spectrometry (LC/MS/MS) method for the simultaneous quantitation of seven UH alkaloids (corynoxeine, isocorynoxeine, rhynchophylline, isorhynchophylline, hirsutine, hirsuteine and geissoschizine methyl ether) in rat plasma and brain. After protein precipitation with acetonitrile, chromatographic separation was performed using an Ascentis Express RP-amide column, with gradient elution with 0.2% formic acid and acetonitrile at 0.3 mL/min. All analytes in the plasma and brain showed good linearity over a wide concentration range (r > 0.995). Intra-day and inter-day variations of each constituent were 8.6 and 8.0% or less in the plasma, and 14.9 and 15.0% or less in the brain, respectively. The validated LC/MS/MS method was applied in the pharmacokinetic studies of UH alkaloids after oral administration of Yokukansan to rats. In the plasma, rhynchophylline, hirsutine, hirsuteine and geissoschizine methyl ether were detected, but only geissoschizine methyl ether was detected in the brain. These results suggest that geissoschizine methyl ether is an important constituent of the pharmacological effects of Yokukansan.

Analyses of anticancer drugs by capillary electrophoresis: a review

Abstract: Capillary electrophoresis is a fast, inexpensive and low detection limit technique for the analysis of anticancer drugs. It has been used to analyze various anticancer drugs in biological samples, pharmaceutical preparations and environmental matrices. It has also been used to detect various cancer biomarkers in cancer patients. The present article describes the state-of-the art of capillary electrophoresis for the analyses of anticancer drugs. Various drugs discussed belong to several groups such as antimitotic agents, nucleoside analogs, antibiotics, topoisomerase inhibitors and DNA intercalating agents. In addition, efforts have also been made to discuss sample preparation, applications of capillary electrophoresis in genomic research, optimization and future perspectives.

Synthesis and application of a chiral ionic liquid functionalized β-cyclodextrin as a chiral selector in capillary electrophoresis

Abstract: A novel chiral ionic liquid functionalized β-cyclodextrin, 6-O-2-hydroxpropyltrimethylammonium-β-cyclodextrin tetrafluoroborate ([HPTMA-β-CD][BF4]), was synthesized and used as a chiral selector in capillary electrophoresis. [HPTMA-β-CD][BF4] not only increased the solubility in aqueous buffer in comparison with the parent compound, but also provided a stable reversal electroosmotic flow, and the enantioseparation of eight chiral drugs was examined in phosphate buffer containing [HPTMA-β-CD][BF4] as the chiral selector. The effects of the [HPTMA-β-CD][BF4] concentration and the background electrolyte pH were studied. Moreover, the chiral separation abilities of β-CD and [HPTMA-β-CD][BF4] were compared and possible mechanisms for the chiral recognition of [HPTMA-β-CD][BF4] are discussed. Copyright © 2013 John Wiley & Sons, Ltd.

Utility of noninvasive biomatrices in pharmacokinetic studies

Abstract: Blood and plasma are the biomatrices traditionally used for drug monitoring and their pharmacokinetic profiling. Blood is the circulating fluid in contact with all organs and tissues of body and thus is the most representative fluid for measuring systemic drug levels. However, venipuncture suffers from the caveat of being an invasive technique which often makes people reluctant to participate in clinical studies. Thus, there is a need for noninvasive bio-fluids that are ethically appropriate, cost-efficient and toxicologically relevant. These alternate bio-fluids may prove clinically useful as alternatives to plasma/serum in therapeutic drug monitoring, pharmacokinetic and toxicokinetic studies, doping control in sports medicine and to monitor local adverse effects. These may be of particular interest in the case of special population groups such as neonates, children, the elderly, terminally ill patients and pregnant or lactating women, and offer the advantage of circumvention of the demand for specialized personnel for sample collection. This review describes such noninvasive bio-fluids (saliva, sweat, tears and milk) that have been considered for pharmacokinetic drug analysis, emphasizing their sample preparation, its associated difficulties and their correlation with plasma.

Combined solid-phase microextraction and high-performance liquid chromatography with ultroviolet detection for simultaneous analysis of clenbuterol, salbutamol and ractopamine in pig samples.

Abstract: A simple and sensitive method based on the combination of solid-phase microextraction (SPME) and high-performance liquid chromatography with ultroviolet detection was developed for the simultaneous determination of clenbuterol, salbutamol and ractopamine in pig samples. Parameters of the SPME procedure affecting extraction efficiency, such as the type of fiber, extraction time, extraction temperature, ion strength, pH of sample and stirring rate, were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.5-50 µg/L for clenbuterol and ractopamine, and 0.2-20 µg/L for salbutamol. The limits of detection were 0.1 µg/L for clenbuterol, 0.05 µg/L for salbutamol and 0.1 μg/L for ractopamine, respectively. The averages of intra- and inter-day accuracy ranged from 79.8 to 92.4%. The intra-day and inter-day precision were below 9.6% for the three analytes. This method exhibited the advantages of simplicity, rapidity and low solvent consumption, and was suitable for the monitoring of β2 -agonists residue in pig samples.

Identification of isoquercitrin metabolites produced by human intestinal bacteria using UPLC‐Q‐TOF/MS

Abstract: Astilbin, mainly isolated from a commonly used herbal medicine, Smilax glabra Roxb (SGR), exhibits a variety of pharmacological activities and biological effects. It is metabolized by intestinal bacteria after oral administration which leads to the variation of ethnopharmacological profile of this traditional medicine. However, little is known on the interactions of this active compound with intestinal bacteria, which would be very helpful in unravelling how SGR works. In this study, different pure bacteria from human feces were isolated and were used to investigate their conversion capability of astilbin. Ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS) technique combined with Metabolynx(TM) software was used to analyze astilbin and its metabolites. The parent compound and two metabolites (quercetin and eriodictyol) were detected in the isolated bacterial samples compared with blank samples. Quercetin was present in Enterococcus sp. 8B, 8-2 and 9-2 samples. Eriodictyol was only identified in Enterococcus sp. 8B sample. The metabolic routes and metabolites of astilbin produced by the different intestinal bacteria are reported for the first time. This will be useful for the investigation of the pharmacokinetic study of astilbin in vivo and the role of different intestinal bacteria in the metabolism of natural compounds.

Screening and determination of drugs in human saliva utilizing microextraction by packed sorbent and liquid chromatography–tandem mass spectrometry

Abstract: This study presents a new method for collecting and handling saliva samples using an automated analytical microsyringe and microextraction by packed syringe (MEPS). The screening and determination ...

Oriented immobilized anti-hIgG via F(c) fragment-imprinted PHEMA cryogel for IgG purification.

Abstract: Antibodies are used in many applications, especially as diagnostic and therapeutic agents. Among the various techniques used for the purification of antibodies, immunoaffinity chromatography is by far the most common. For this purpose, oriented immobilization of antibodies is an important step for the efficiency of purification step. In this study, F(c) fragment-imprinted poly(hydroxyethyl methacrylate) cryogel (MIP) was prepared for the oriented immobilization of anti-hIgG for IgG purification from human plasma. Non-imprinted poly(hydroxyethyl methacrylate) cryogel (NIP) was also prepared for random immobilization of anti-hIgG to compare the adsorption capacities of oriented (MIP/anti-hIgG) and random (NIP/anti-hIgG) cryogel columns. The amount of immobilized anti-hIgG was 19.8 mg/g for the NIP column and 23.7 mg/g for the MIP column. Although the amount of immobilized anti-hIgG was almost the same for the NIP and MIP columns, IgG adsorption capacity was found to be three times higher than the NIP/anti-hIgG column (29.7 mg/g) for the MIP/anti-hIgG column (86.9 mg/g). Higher IgG adsorption capacity was observed from human plasma (up to 106.4 mg/g) with the MIP/anti-hIgG cryogel column. Adsorbed IgG was eluted using 1.0 M NaCl with a purity of 96.7%. The results obtained here are very encouraging and showed the usability of MIP/anti-hIgG cryogel prepared via imprinting of Fc fragments as an alternative to conventional immunoaffinity techniques for IgG purification.

Identification and profiling of targeted oxidized linoleic acid metabolites in rat plasma by quadrupole time-of-flight mass spectrometry.

Abstract: Linoleic acid (LA) and LA-esters are the precursors of LA hydroperoxides, which are readily converted to 9- and 13-hydroxy-​octadecadienoic acid (HODE) and 9- and 13-oxo-​octadecadienoic acid (oxo ODE) metabolites in vivo. These four oxidized LA metabolites (OXLAMs) have been implicated in a variety of pathological conditions. Therefore, their accurate measurement may provide mechanistic insights into disease pathogenesis. Here we present a novel quadrupole time-of-flight mass spectrometry (Q-TOFMS) method for quantitation and identification of target OXLAMs in rat plasma. In this method, the esterified OXLAMs were base-hydrolyzed and followed by liquid-liquid extraction. Quantitative analyses were based on one-point standard addition with isotope dilution. The Q-TOFMS data of target metabolites were acquired and multiple reaction monitoring extracted-ion chromatograms were generated post-acquisition with a 10 ppm extraction window. The limit of quantitation was 9.7-35.9 nmol/L depending on the metabolite. The method was reproducible with a coefficient of variation of 0.991. Concentrations of 9-HODE, 13-HODE, 9-oxoODE and 13-oxoODE were 84.0, 138.6, 263.0 and 69.5 nmol/L, respectively, which were consistent with the results obtained from one-point standard addition. Target metabolites were simultaneously characterized based on the accurate Q-TOFMS data. This is the first study of secondary LA metabolites using Q-TOFMS. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

The biotransformation of oleuropein in rats

Abstract: A highly sensitive and specific LC-MS/MS method was developed to investigate the in vivo bio-transformation of oleuropein in rat. Rat feces and urine samples collected after oral administration were determined by liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the negative-ion mode. The assay procedure involves a simple liquid-liquid extraction of parent oleuropein and the metabolite from rat feces and urine with ethyl acetate. Chromatographic separation was operated with 0.1% formic acid aqueous and methanol in gradient program at a flow rate of 0.50 mL/min on an RP-C18 column with a total run time of 31 min. This method was successfully applied to simultaneous determination of oleuropein and its metabolites in rat feces and urine. De-glucosylation, hydrolysis, oxygenation and methylation were found to comprise the major metabolic pathway of oleuropein in rat gastrointestinal tract and three metabolites were absorbed into the blood circulatory system within 24 h after oral administration.

Simultaneous quantification of tramadol and O-desmethyltramadol in hair samples by gas chromatography-electron impact/mass spectrometry.

Abstract: Over recent years, hair has become the ideal matrix for retrospective investigation of chronic abuse, including for tramadol. However, in order to exclude the possibility of external contamination, it is also important to quantify simultaneously its main metabolite, O-desmethyltramadol (M1), which presence in hair reflects systemic exposure. In the present study a methodology aimed at the simultaneous quantification of tramadol and M1 in human hair was developed and validated for the first time. After decontamination of hair samples (60 mg), tramadol and M1 were extracted with methanol in an ultrasonic bath (~5 h). Purification was performed by solid-phase extraction using mixed-mode extraction cartridges. Subsequently to derivatization, analysis was performed by gas chromatography-electron impact/mass spectrometry (GC-EI/MS). The method proved to be selective. The regression analysis for both analytes was shown to be linear in the range of 0.1-20.0 ng/mg with correlation coefficients of 0.9995 and 0.9997 for tramadol and M1, respectively. The coefficients of variation oscillated between 3.85 and 13.24%. The limits of detection were 0.03 and 0.02 ng/mg, and the lower limits of quantification were 0.08 and 0.06 ng/mg for tramadol and M1, respectively. The proof of applicability was performed in hair samples from six patients undergoing tramadol therapy. All samples were positive for tramadol and M1.

Rapid and simultaneous determination of multiple classes of abused drugs and metabolites in human urine by a robust LC-MS/MS method – application to urine drug testing in pain clinics

Abstract: A simple LC-MS/MS method was developed and validated for quantitatively analyzing six classes of 26 abused drugs and metabolites in human urine: (1) illicit drugs; (2) opiates; (3) synthetic opioids; (4) sedative; (5) stimulants; and (6) γ-aminobutyric acid analogs. All urine samples were diluted with a mixture of isotope-labeled internal standards, hydrolyzed with β-glucuronidase and directly injected in a gradient chromatographic run. The mobile phase was composed of 0.1% formic acid in water and 0.1% of formic acid in methanol. A 4.9 min run time using the multiplexing driver and ultra-biphenyl column (50 × 2.1 mm, 5 µm, RESTEK) allowed all drugs to have sufficient resolution in a short elute time. The overlapping liquid chromatography runs and scheduled multiple reaction monitoring acquisition method resulted in a higher overall throughput for the system. The result was linear over the studied range (2–16,000 ng/mL) for all compounds with correlation coefficients r2 ≥ 0.995. The intra-day and inter-day precisions and accuracies were within 15% and recovery was between 83 and 115% for all analytes. Freeze–thaw stability for three cycles and long-term stability (57 days, −20°C) were established for all analytes. The cross-validation between College of American Pathologists and in-house was validated (0.06% ≤ bias ≤ 12.3%). The applicability of the method was examined by analyzing urine samples from chronic pain patients (n = 610). Copyright © 2013 John Wiley & Sons, Ltd.

Improved RP‐HPLC method for determination of bovine lactoferrin and its proteolytic degradation in simulated gastrointestinal fluids

Abstract: The objective of this study was to qualitatively and quantitatively evaluate bovine lactoferrin (bLf) and its stability using a rapid RP-HPLC method. bLf could be rapidly detected within 20 min and quantitated at levels down to 5 µg/mL, and the equation of linearity was y = 86.10x + 178.31 with the correlation coefficient (r(2)) 0.9997. Quantitative data obtained in the present study proved the improved RP-HPLC method to be a sensitive and accurate analytical tool for bLf determination. The proteolytic cleavage of bLf in simulated human gastrointestinal fluids was further analyzed by RP-HPLC, and found to follow pseudo-first-order kinetics. The typical equation obtained by pepsin was log(10) [A(t)]/[A(0)] = -0.03x (r(2) = 0.85), and log(10) [A(t)]/[A(0)] = -0.01x (r(2) = 0.81) for trypsin and chymotrypsin combination. Pepsinolysis of bLf in simulated gastric fluid was relatively fast with the half-life t(1/2) 23.1 min. The digestion of bLf in simulated intestinal fluid was slower with about a 3-fold increase in half-life (69.3 min). After the complete proteolysis of bLf, small cleaved peptide fragments were fully separated and identified by RP-HPLC. The proteolytic study indicated that this validated RP-HPLC was able to evaluate bLf stability though monitoring the derivatization products.

Analytical approach to determine biogenic amines in urine using microextraction in packed syringe and liquid chromatography coupled to electrochemical detection

Abstract: The goal of this work was to develop and validate an analytical method for the detection and quantification of thebiogenicaminesserotonin(5-HT),dopamine(DA)andnorepinephrine(NE),usingmicroextractioninpacked syringe (MEPS) andliquid chromatography coupled to electrochemical detection (HPLC-ED) in urine. The method was validated according to inter-nationally accepted guidelines from the Food and Drug Administration. Linearity was established between 50 and 1000 ng/mLfor5-HTand between5and 1000ng/mLforDAand NE, withdeterminationcoefficients(R 2 )>0.99forall compounds.Thelimitsof quantification and detection were respectively 50 and 20 ng/mL for 5-HT, and 5 and 2 ng/mL for DA and NE. Within- andbetween-runprecision ranged from0.84 to 9.41%, while accuracy ranged from0.79 to 12.76%for all compounds. The interme-diate precision and accuracy were 1.50–8.36 and 0.54–13.51%, respectively. The method was found suitable for clinicalroutine analysis of the studied compounds, using a sample volume of 0.5 mL. This is thefirst study employing a commer-cially available MEPS column for the simultaneous detection and quantification of 5-HT, DA and NE in urine by coulometricdetection. Copyright © 2012 John Wiley & Sons, Ltd.Keywords: biogenic amines; urine; MEPS; HPLC-ED

Bacteriocin activity against various pathogens produced by Pediococcus pentosaceus VJ13 isolated from Idly batter

Abstract: Bacteriocins, an antimicrobial peptide, is known to have wide spectrum antimicrobial activity against various pathogens. Because they are easily digested in the intestine, they are considered as safe and are widely used as food preservatives. Hence their purification and characterization have attracted considerable attraction, especially for those having activity against human pathogens. In this study, the bacteriocin produced by Pediococcus pentosaceus VJ13 was precipitated with cold acetone and purified by gel permeation chromatography and hydrophobic interaction chromatography. The bacteriocin exhibited antimicrobial activity against various pathogens, like Mycobacterium smegmatis, Klebsiella pneumonia, Clostridium perfringens and Staphylococcus epidermidis. The activity of bacteriocin was lost completely after treatment with protease, which revealed its proteinaceous nature. The bacteriocin was stable up to 100°C and exhibited antilisterial property which is a characteristic feature of class IIa bacteriocins. It was active within the pH range of 2-8 and stable against various chemicals and denaturants. Tricine SDS-PAGE revealed its molecular weight to be 4.0 kDa, where the corresponding activity against Listeria monocytogenes was also noted. Treatment of L. monocytogenes with bacteriocin decreased the viable cell count, and scanning electron microscope analysis revealed membrane pore formation that resulted in the release of intracellular content, suggesting its bactericidal effect.

Comprehensive fluorogenic derivatization-liquid chromatography/tandem mass spectrometry proteomic analysis of colorectal cancer cell to identify biomarker candidate.

Abstract: Existing colorectal cancer biomarkers are insufficient for providing a quick and accurate diagnosis, which is critical for a good prognosis. More appropriate biomarkers are thus needed. To identify new colorectal cancer biomarker candidates, we conducted a comprehensive differential proteomic analysis of six cancer cell lines and a normal cell line, utilizing a fluorogenic derivatization-liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS) approach. Two sets of intracellular biomarker candidates were identified: one for colorectal cancer, and the other for metastatic colorectal cancer. Our results suggest that cooperative expression of FABP5 and cyclophilin A might be linked to Her2 signaling. Upregulation of LDHB and downregulation of GAPDH suggest the existence of a specific nonglycolytic energy production pathway in metastatic colorectal cancer cells. Downregulation of 14-3-3ζ/δ, cystatin-B, Ran and thioredoxin could be a result of their secretion, which then stimulates metastasis via activity in the sera and ascitic fluids. We propose a possible flow scheme to describe the dynamics of protein expression in colorectal cancer cells leading to tumor progression and metastasis via cell proliferation, angiogenesis, disorganization of actin filaments and epithelial-mesenchymal transition. Our results suggest that colorectal tumor progression may be regulated by signaling mediated by Her2, hypoxia, and TGFβ.

A sensitive LC-MS/MS method for the simultaneous determination of amoxicillin and ambroxol in human plasma with segmental monitoring.

Abstract: Amoxicillin (AMO) degrades in plasma at room temperature and readily undergoes hydrolysis by the plasma amidase. In this paper, a novel, rapid and sensitive LC-MS/MS method operated in segmental and multiple reaction monitoring has been developed for the simultaneous determination of amoxicillin and ambroxol in human plasma. The degradation of amoxicillin in plasma was well prevented by immediate addition of 20 μL glacial acetic acid to 200 μL aliquot of freshly collected plasma samples before storage at −80°C. The sensitivity of the method was improved with segmental monitoring of the analytes, and lower limits of quantitation of 0.5 ng/mL for ambroxol and 5 ng/mL for amoxicillin were obtained. The sensitivity of our method was five times better than those of the existing methods. Furthermore, the mass response saturation problem with amoxicillin was avoided by diluting the deproteinized plasma samples with water before injection into the LC-MS/MS system. The method was successfully employed in a pharmacokinetic study of the compound amoxicillin and ambroxol hydrochloride tablets. Copyright © 2012 John Wiley & Sons, Ltd.

Identification of bio-active metabolites of gentiopicroside by UPLC/Q-TOF MS and NMR

Abstract: Gentiopicroside (GPS), the main bioactive component in Gentiana scabra Bge., has attracted our attention owing to its high bioactivity, especially the treatment of hepatobiliary disorders. The aglycone form of GPS, a typical secoiridoid glycoside, is considered to be more readily absorbed than its parent drug. This study aimed to identify and characterize the metabolites after GPS incubated with β-glucosidase in buffer solution at 37°C. Samples of biotransformed solution were collected and analyzed by ultraperformance liquid chromatography (UPLC)/quadrupole-time-of-flight mass spectrometry (Q-TOF MS). A total of four metabolites were detected: two were isolated and elucidated by preparative-HPLC and NMR techniques, and one of those four is reported for the first time. The mass spectral fragmentation pattern and accurate masses of metabolites were established on the basis of UPLC/Q-TOF MS analysis. Structure elucidation of metabolites was achieved by comparing their fragmentation pattern with that of the parent drug. A fairly possible metabolic pathway of GPS by β-glucosidase was proposed. The hepatoprotective activities of metabolites M1 and M2 were investigated and the results showed that their hepatoprotective activities were higher than that of parent drug. Our results provided a meaningful basis for discovering lead compounds from biotransformation related to G. scabra Bge. in traditional Chinese medicine.

Ionic liquids dispersive liquid–liquid microextraction and high-performance liquid chromatographic determination of irbesartan and valsartan in human urine

Abstract: An environmentally friendly ionic liquids dispersive liquid–liquid microextraction (IL-DLLME) method coupled with high-performance liquid chromatography (HPLC) for the determination of antihypertensive drugs irbesartan and valsartan in human urine samples was developed. The HPLC separations were accomplished in less than 10 min using a reversed-phase C18 column (250 × 4.60 mm i.d., 5 µm) with a mobile phase containing 0.3 % formic acid solution and methanol (v/v, 3:7; flow rate, 1.0 mL/min). UV absorption responses at 236 nm were linear over a wide concentration range from 50 µg/mL to the detection limits of 3.3 µg/L for valsartan and 1.5 µg/L for irbesartan. The effective parameters on IL-DLLME, such as ionic liquid types and their amounts, disperser solvent types and their volume, pH of the sample and extraction time were studied and optimized. The developed IL-DLLME-HPLC was successfully applied for evaluation of the urine irbesartan and valsartan profile following oral capsules administration. Copyright © 2012 John Wiley & Sons, Ltd.

Isolation of volatiles from Nigella sativa seeds using microwave‐assisted extraction: effect of whole extracts on canine and murine CYP1A

Abstract: The volatile components of Nigella sativa seeds were isolated using microwave-assisted extraction (MAE) and identified using gas chromatography. Further investigations were carried out to demonstrate the effects of whole extracts on canine (dog) and murine (rat) cytochrome P450 1A (CYP1A). The optimal extraction conditions of MAE were as follows: 25 mL of water, medium level of microwave oven power and 10 min of extraction time. A total of 32 compounds were identified under the conditions using GC-FID and GC-MS. Thymoquinone (38.23%), p-cymene (28.61%), 4-isopropyl-9-methoxy-1-methyl-1-cyclohexene (5.74%), longifolene (5.33%), α-thujene (3.88) and carvacol (2.31%) were the main compounds emitted from N. sativa seeds. Various extracts including pure compounds, essential oil, nonpolar partition, relatively high-polar/nonpolar partition, and polar partition extracts effectively inhibited the reaction of ethoxyresorufin O-de-ethylation, which is specified for CYP1A activity both in dog and rat. This in vitro data should be heeded as a signal of possible in vivo interactions. The use of human liver preparations would considerably strengthen the practical impact of the data generated from this study.

Sensitive profiling of biogenic amines in human urine by capillary electrophoresis with field amplified sample injection

Abstract: In order to monitor biogenic amines in human urine, a method based on field-amplified sample injection combined with capillary electrophoresis and direct UV absorption detection was developed. Dopamine, tyramine, tryptamine, serotonin and epinephrine were effectively separated and identified in human urine samples, and detection limits were 0.072, 0.010, 0.027, 0.010 and 0.120 µmol/L, respectively. Detection limits comparable to laser-induced fluorescence detection or solid phase extraction combined with capillary electrophoresis were achieved. Parameters affecting electrophoretic system detection sensitivity were investigated. Optimal separation conditions were obtained using as background electrolyte a pH 6.5 mixture of 2-(morpholino)ethanesulfonic acid 20 mmol/L and 30 mmol/L phosphate buffer, containing 0.05% hydroxypropylcellulose and 10% v/v methanol. Injections of the sample solution were performed by applying a voltage of 12 kV for 50 s. Recovery and accuracy ranged between 89.4 and 94.9%, and 89 and 112%, respectively. The method was successfully applied on actual urine samples (from a healthy volunteer): target bioamine content was consistent with endogenous levels reported in the literature. The proposed method is simple, fast and inexpensive and can be conveniently employed in work-related stress studies. The affordability and noninvasive sampling of the method allow epidemiological studies on large number of exposed persons to be performed. Copyright © 2013 John Wiley & Sons, Ltd.

Comparative pharmacokinetic studies of andrographolide and its metabolite of 14-deoxy-12-hydroxy-andrographolide in rat by ultra-performance liquid chromatography-mass spectrometry.

Abstract: Andrographolide (AND), one of the major diterpenoids from Andrographis paniculata (Burm. f.) Nees, can be metabolized as a phase two metabolite of 14-deoxy-12-hydroxy-andrographolide-19-O-β-d-glucuronide in human. The aim of this study is to characterize and synthesize the phase one metabolite of 14-deoxy-12-hydroxy-andrographolide (DEO-AND) after gavage feeding of AND in rats, and to compare the pharmacokinetics of AND and DEO-AND after intravenous administration. DEO-AND was first discovered existing in rat serum by HPLC-MS(n) after administration of AND. Furthermore, the target metabolite was synthesized and elucidated by NMR. In addition, a rapid, selective and sensitive UPLC-ESI/MS method was developed for the first time to determine the content of AND and DEO-AND in rats serum. The method was successfully applied to a pharmacokinetic study in rats after a single intravenous dose of 5 mg/kg AND and DEO-AND, respectively. In comparison, the pharmacokinetic parameters of metabolite DEO-AND, including distribution rate constant, elimination rate constant, half-life and mean residence time, were significantly less than those of AND (p < 0.05). However, the AUC0→720 min value after intravenous administration of DEO-AND was 781.59 ± 81.46 µg min/mL, which was 17.71 times higher than that of AND (44.13 ± 10.45 µg min/mL; p < 0.05). These results show the pharmacokinetic profile of AND to be significantly different from that of DEO-AND by intravenous administration.