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Main Metabolites (main + metabolite)
Selected AbstractsP71 Metabolism of delta-3-Carene by human cytochrom 450 enzymesCONTACT DERMATITIS, Issue 3 2004Mike Duisken Occupational exposure to monoterpenes occurs in saw mills, particle-board plants, carpentry shops and other types of wood-treating industries. The bicyclic monoterpene delta-3-Carene, one of the components of turpentine, may irritate the skin and muceous membranes and prolonged exposure may result in allergic contact dermatitis or chronic lung function impairment. The effects of low concentrations of delta-3-Carene on alveolar macrophages in vitro were examined and a dose-dependent relationship between the cell viability and the delta-3-Carene concentration was found. Little is known about the metabolism of delta-3-Carene in mammalians. In order to determine the toxic potential of this monoterpene we studied the human metabolism of delta-3-Carene in vitro. Therefore we used pooled human liver S9 and human liver microsomal cytochrome P450 enzymes. By using GC-MS analysis we found one main metabolite produced at high rates. The structure was identified by its mass spectra. The mass fragmentation indicated hydroxylation in allyl position. After synthesis of the assumed product in a four step reaction, it was characterized as delta-3-Carene-10-ol. There was a clear correlation between the concentration of the metabolite production, incubation time and enzyme concentration, respectively. Kinetic analysis showed that Km and Vmax values for the oxidation of delta-3-Carene by human liver microsomes were 0.39 ,M and 0.2 nmol/min/nmol P450. It is the first time that delta-3-Carene-10-ol is described as human metabolite of delta-3-Carene. [source] Pharmacokinetics of dipeptidylpeptidase-4 inhibitorsDIABETES OBESITY & METABOLISM, Issue 8 2010A. J. Scheen Type 2 diabetes (T2DM) is a complex disease combining defects in insulin secretion and insulin action. New compounds have been developed for improving glucose-induced insulin secretion and glucose control, without inducing hypoglycaemia or weight gain. Dipeptidylpeptidase-4 (DPP-4) inhibitors are new oral glucose-lowering agents, so-called incretin enhancers, which may be used as monotherapy or in combination with other antidiabetic compounds. Sitagliptin, vildaglipin and saxagliptin are already on the market in many countries, either as single agents or in fixed-dose combined formulations with metformin. Other DPP-4 inhibitors, such as alogliptin and linagliptin, are currently in late phase of development. The present paper summarizes and compares the main pharmacokinetics (PK) properties, that is, absorption, distribution, metabolism and elimination, of these five DPP-4 inhibitors. Available data were obtained in clinical trials performed in healthy young male subjects, patients with T2DM, and patients with either renal insufficiency or hepatic impairment. PK characteristics were generally similar in young healthy subjects and in middle-aged overweight patients with diabetes. All together gliptins have a good oral bioavailability which is not significantly influenced by food intake. PK/pharmacodynamics characteristics, that is, sufficiently prolonged half-life and sustained DPP-4 enzyme inactivation, generally allow one single oral administration per day for the management of T2DM; the only exception is vildagliptin for which a twice-daily administration is recommended because of a shorter half-life. DPP-4 inhibitors are in general not substrates for cytochrome P450 (except saxagliptin that is metabolized via CYP 3A4/A5) and do not act as inducers or inhibitors of this system. Several metabolites have been documented but most of them are inactive; however, the main metabolite of saxagliptin also exerts a significant DPP-4 inhibition and is half as potent as the parent compound. Renal excretion is the most important elimination pathway, except for linagliptin whose metabolism in the liver appears to be predominant. PK properties of gliptins, combined with their good safety profile, explain why no dose adjustment is necessary in elderly patients or in patients with mild to moderate hepatic impairment. As far as patients with renal impairment are concerned, significant increases in drug exposure for sitagliptin and saxagliptin have been reported so that appropriate reductions in daily dosages are recommended according to estimated glomerular filtration rate. The PK characteristics of DPP-4 inhibitors suggest that these compounds are not exposed to a high risk of drug,drug interactions. However, the daily dose of saxagliptin should be reduced when coadministered with potent CYP 3A4 inhibitors. In conclusion, besides their pharmacodynamic properties leading to effective glucose-lowering effect without inducing hypoglycaemia or weight gain, DPP-4 inhibitors show favourable PK properties, which contribute to a good efficacy/safety ratio for the management of T2DM in clinical practice. [source] Determination of 13C/12C ratios of urinary excreted boldenone and its main metabolite 5,-androst-1-en-17,-ol-3-oneDRUG TESTING AND ANALYSIS, Issue 5 2010Thomas Piper Abstract Boldenone (androsta,1,4,dien,17,,ol,3,one, Bo) is an anabolic steroid known to have been used in cattle breeding or equine sport as a doping agent for many years. Although not clinically approved for human application, Bo or its main metabolite 5,-androst-1-en-17,-ol-3-one (BM1) were detected in several doping control samples. For more than 15 years the possibility of endogenous Bo production in human beings has been discussed. This is a challenging issue for doping control laboratories as Bo belongs to the list of prohibited substances of the World Anti-Doping Agency and therefore the chance for false positive testing is significant. By GC/C/IRMS (gas chromatography/combustion/isotope ratio mass spectrometry) it should be possible to analyze the 13C/12C ratio of either Bo or BM1 and to distinguish whether their source is endogenous or exogenous. Therefore a method was developed to determine the 13C/12C ratios of Bo, BM1, pregnanediol, androsterone, etiocholanolone, and testosterone from a single urine specimen. The validity of the method was ensured by repeated processing of urine fortified with 2,50 ng/mL Bo and BM1. The specificity of the method was ensured by gas chromatography/mass spectrometry determinations. Out of 23 samples investigated throughout the last four years, 11 showed 13C/12C ratios of Bo or BM1 inconsistent with an exogenous origin. Two of these samples were collected from the same athlete within a one-month interval, strongly indicating the chance of endogenous Bo production by this athlete. Copyright © 2010 John Wiley & Sons, Ltd. [source] Catalytic Voltammetric Determination of Cladribine in Biological SamplesELECTROANALYSIS, Issue 5-6 2003Noemí de-los-Santos-Álvarez Abstract An electrochemical method for the citotoxic prodrug cladribine determination is proposed. Graphite electrodes modified with cladribine showed a redox process with a formal potential of 0.173,V at pH 6, after the oxidation of the adenine moiety of the drug, whose current can be employed as analytical signal with a detection limit of 75,nM by square-wave voltammetry. As these oxidation products exhibit great electrocatalytic activity toward the electro-oxidation of NADH at low potentials, the analytical response can further be amplified. As a result, the detection limit was improved up to 1,nM using differential pulse voltammetry. The method was applied to the determination of cladribine in serum and urine samples after solid-phase extraction. No electroactive interferences were found in both fluids. The method allows the selective detection of the drug in the presence of the main metabolite, 2-chloroadenosine, which is not able to electrocatalize the NADH oxidation. [source] DNA damage in leukocytes of workers occupationally exposed to arsenic in copper smeltersENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2005Jadwiga Palus Abstract Inorganic arsenic (i-As) is a known human carcinogen; however, humans continue to be exposed to i-As in drinking water and in certain occupational settings. In this study, we used the Comet assay to evaluate DNA damage in the somatic cells of workers from three Polish copper smelters who were occupationally exposed to i-As. Blood samples were collected from 72 male workers and 83 unexposed male controls and used for the detection of DNA damage, oxidative DNA damage, and DNA damage after a 3-hr incubation in culture. Urine samples were collected to assess the level of exposure. The mean concentration of arsenic metabolites in urine [the sum of arsenite (AsIII), arsenate (AsV), monomethylarsenate (MMA) and dimethylarsenate (DMA)] and the concentrations of DMA (the main metabolite in urine) were higher in workers than in controls, but the differences were not statistically significant. By contrast, the level of DNA damage, expressed as the median tail moment, was significantly higher in the leukocytes of workers than in the controls. Comet assays conducted with formamidopyrimidine glycosylase (FPG) digestion to detect oxidative DNA damage indicated that oxidative lesions were present in leukocytes from both the exposed and control groups, but the levels of damage were significantly higher among the workers. Incubation of the cells in culture resulted in a significant reduction in the levels of DNA damage, especially among leukocytes from the workers, suggesting that the DNA damage was subject to repair. Our findings indicate that copper smelter workers have increased levels of DNA damage in somatic cells, suggesting a potential health risk for the workers. Although i-As was present in air samples from the smelters and in urine samples from workers, no clear association could be made between i-As exposure and the DNA damage. Environ. Mol. Mutagen., 2005. © 2005 Wiley-Liss, Inc. [source] Metabolism of fluoranthene in different plant cell cultures and intact plantsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2000Marit Kolb Abstract The metabolism of fluoranthene was investigated in 11 cell cultures of different plant species using a [14C]-labeled standard. Most species metabolized less than 5% of fluoranthene to soluble metabolites and formed less than 5% nonextractable residues during the standardized 48-h test procedure. Higher metabolic rates were observed in lettuce (Lactuca sativa, 6%), wheat (Tricitum aestivum, 9%), and tomato (Lycopersicon esculentum, 15%). A special high metabolic rate of nearly 50% was determined for the rose species Paul's Scarlet. Chromatographic analysis of metabolites extracted from aseptically grown tomato plants proved that the metabolites detected in the cell cultures were also formed in the intact plants. Metabolites produced in tomato and rose cells from [14C]-fluoranthene were conjugated with glucose, glucuronic acid, and other cell components. After acid hydrolyses, the main metabolite of both species was 1-hydroxyfluoranthene as identified by gas chromatography,mass spectrometry and high-performance liquid chromatography with diode array detection. The second metabolite formed by both species was 8-hydroxy-fluoranthene. A third metabolite in tomatoes was 3-hydroxyfluoranthene. [source] COX-2, but not COX-1, activity is necessary for the induction of perforant path long-term potentiation and spatial learning in vivoEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008T. R. Cowley Abstract The objectives of this research were to investigate the role played by the enzyme cyclooxygenase (COX) in learning and memory, synaptic plasticity and synaptic transmission in the rat brain in vivo. Male Wistar rats were treated with isoform-selective inhibitors for COX-1 and COX-2, either chronically and tested in the watermaze or acutely before electrophysiological recordings were made. We found a significant impairment in acquisition of the watermaze with inhibition of COX-2. Furthermore, we found COX-2 but not COX-1 inhibition significantly blocked long-term potentiation (LTP) induction but had no effect on already established LTP. Moreover, exogenous replacement of the main metabolite of COX-2 activity, PGE2, was sufficient to restore LTP induction and for normal downstream signalling to ensue, namely extracellular signalling-regulated kinase (ERK)-phosphorylation and c-FOS expression. We conclude that endogenous basal levels of PGE2 resulting from COX-2 but not COX-1 activity are necessary for synaptic plasticity and memory acquisition. [source] Withanoside IV and its active metabolite, sominone, attenuate A,(25,35)-induced neurodegenerationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2006Tomoharu Kuboyama Abstract At the present, medication of dementia is limited to symptomatic treatments such as the use of cholinesterase inhibitors. To cure dementia completely, that is regaining neuronal function, reconstruction of neuronal networks is necessary. Therefore, we have been exploring antidementia drugs based on reconstructing neuronal networks in the damaged brain and found that withanoside IV (a constituent of Ashwagandha; the root of Withania somnifera) induced neurite outgrowth in cultured rat cortical neurons. Oral administration of withanoside IV (10 µmol/kg/day) significantly improved memory deficits in A,(25,35)-injected (25 nmol, i.c.v.) mice and prevented loss of axons, dendrites, and synapses. Sominone, an aglycone of withanoside IV, was identified as the main metabolite after oral administration of withanoside IV. Sominone (1 µm) induced axonal and dendritic regeneration and synaptic reconstruction significantly in cultured rat cortical neurons damaged by 10 µm A,(25,35). These data suggest that orally administrated withanoside IV may ameliorate neuronal dysfunction in Alzheimer's disease and that the active principle after metabolism is sominone. [source] Itraconazole oral solution and intravenous formulations: a review of pharmacokinetics and pharmacodynamicsJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 3 2001L. Willems Itraconazole is a triazole antifungal agent with a broad spectrum of activity. It is well tolerated and highly efficacious, particularly because its main metabolite, hydroxy-itraconazole, also has considerable antifungal activity. Two new formulations of itraconazole, an oral solution and an intravenous formulation, have recently been developed, which combine lipophilic itraconazole with cyclodextrin. These formulations have improved the solubility of itraconazole, leading to enhanced absorption and bioavailability compared with the original capsule formulation, without having an impact on the tolerability profile of itraconazole. The oral solution and intravenous formulations of itraconazole produce consistent plasma concentrations and are ideal for the treatment of systemic fungal infections in a wide range of patient populations. The additional flexibility offered by the different routes of administration means that itraconazole treatment can be specifically tailored for use in all patients, including children and those requiring intensive care. [source] Characterization of metabolites of tanshinone IIA in rats by liquid chromatography/tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2006Peng Li Abstract The metabolism of tanshinone IIA was studied in rats after a single-dose intravenous administration. In the present study, 12 metabolites of tanshinone IIA were identified in rat bile, urine and feces with two LC gradients using LC-MS/MS. Seven phase I metabolites and five phase II metabolites of tanshinone IIA were characterized and their molecular structures proposed on the basis of the characteristics of their precursor ions, product ions and chromatographic retention time. The seven phase I metabolites were formed, through two main metabolic routes, which were hydroxylation and dehydrogenation metabolism. M1, M4, M5 and M6 were supposedly tanshinone IIB, hydroxytanshinone IIA, przewaquinone A and dehydrotanshinone IIA, respectively, by comparing their HPLC retention times and mass spectral patterns with those of the standard compounds. The five phase II metabolites identified in this research were all glucuronide conjugates, all of which showed a neutral loss of 176 Da. M9 and M12 were more abundant than other identified metabolites in the bile, which was the main excretion path of tanshinone IIA and the metabolites. M12 was the main metabolite of tanshinone IIA. M9 and M12 were proposed to be the glucuronide conjugates of two different semiquinones and these semiquinones were the hydrogenation products of dehydrotanshinone IIA and tanshinone IIA, respectively. This hydrogenized reaction may be catalyzed by the NAD(P)H: quinone acceptor oxidoreductase (NQO). The biotransformation pathways of tanshinone IIA were proposed on the basis of this research. Copyright © 2006 John Wiley & Sons, Ltd. [source] Pharmacokinetics of flubendazole and its metabolites in lambs and adult sheep (Ovis aries)JOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2009Flubendazole (FLU) is indicated for control of helminthoses in pig and avian species (monogastric animals) and its corresponding pharmacokinetics are well known. The information on FLU's pharmacokinetic behavior in animal species with forestomach (ruminants) has been limited although the use of FLU in these species could be beneficial. The aim of this study was to investigate the pharmacokinetics of FLU and its main metabolites in sheep. The effects of animal age (sexually immature and mature ones) and gender were also studied. FLU was orally administered in a single experimental dose (30 mg/kg of body weight) in the form of oral suspension. Treated immature animals (aged 3 months) and 5 months later the same mature individuals (aged 8 months) were kept under the same conditions (food, water and management) and treated with FLU. Within 72 h after FLU administration, plasmatic samples were collected and FLU and its Phase I metabolites were quantified using high-performance liquid chromatography. FLU was detected in very low concentrations only, reduced FLU (FLU-R) was identified as the main metabolite, and hydrolyzed FLU (FLU-H) as the minor one. Formation of FLU-R was stereospecific with (+)-FLU-R domination. The plasmatic concentrations of (+)-FLU-R reached 10,15 times higher values than those of FLU, (,)-FLU-R and FLU-H. A significant gender effect on pharmacokinetics of FLU or (+)-FLU-R metabolite in the mature animals was found and a wide significant difference between lambs and adult sheep in FLU including both metabolites has been proved. [source] In vitro and in vivo pharmacodynamic properties of the fluoroquinolone ibafloxacinJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2002M. Coulet The pharmacodynamic properties of a new veterinary fluoroquinolone antimicrobial agent, ibafloxacin, were evaluated. Minimal inhibitory concentrations (MIC), time-kill kinetics, postantibiotic effect (PAE) and postantibiotic subminimal inhibitory concentration effects (PA-SME) were determined against pathogenic canine Gram-negative and Gram-positive bacterial isolates from dermal, respiratory and urinary tract infections. The synergistic interactions between ibafloxacin and its main metabolite, 8-hydroxy-ibafloxacin were investigated. Finally, the efficacy of ibafloxacin was tested in in vivo canine infection models. Ibafloxacin had good activity against Pasteurella spp., Escherichia coli, Klebsiella spp., Proteus spp. and Staphylococcus spp. (MIC90=0.5 µg/mL), moderate activity against Bordetella bronchiseptica, Enterobacter spp. and Enterococcus spp. (MIC50=4 µg/mL) and low activity against Pseudomonas spp. and Streptococcus spp. The time-killing analysis confirmed that ibafloxacin was bactericidal with a broad spectrum of activity. The PAE and PA-SME were between 0.7,2.13 and 1,11.5 h, respectively. Finally, studies in dog models of wound infection and cystitis confirmed the efficacy of once daily oral ibafloxacin at a dosage of 15 mg/kg. Additional studies are needed to better define the importance of AUC/MIC (AUIC) and Cmax/MIC ratios on the outcome of fluoroquinolone therapy in dogs. [source] Sensitive high-performance liquid chromatography/mass spectrometry method for determination of steviol in rat plasmaRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2004L. Z. Wang The main toxicological concern of stevioside, a highly potent sweetener from S. rebaudiana, is its main metabolite, steviol. To determine very low levels of steviol in in vivo experiments, a sensitive liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) method was developed for quantifying steviol in rat plasma after oral administration of a single dose of stevioside (0.5,g/kg). The sample preparation uses liquid-liquid extraction with tert -butyl methyl ether in an acidic environment. The retention time of steviol was 10.5 min. The assay was linear over the range 2,1000,ng/mL with a lower limit of detection of 1,ng/mL. The intra- and inter-day precision were <5 and <7%, respectively, and the accuracy was in the range 95,108%. The steviol concentration profile in rat plasma was determined. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effects of Ethanol on Synthesis of Prostaglandin F2, in Bovine FemalesREPRODUCTION IN DOMESTIC ANIMALS, Issue 5 2010FRO De Barros Contents Ethanol stimulates the production of prostaglandins in many species. The purpose of this study was to verify the effect of ethanol on the production of prostaglandin F2, (PGF2,) and luteolysis in bovine females. In the first experiment, Holstein cows at day 17 of the oestrous cycle were treated with 100% ethanol (0.05 ml/kg of body weight, IV; n = 5), saline (0.05 ml/kg of body weight, IV; n = 4) or synthetic prostaglandin (150 ,g of D-cloprostenol/cow, IM; n = 4). The plasma concentrations of 13, 14-dihydro-15-keto PGF2, (PGFM; the main metabolite of PGF2, measured in the peripheral blood) were assessed by radioimmunoassay (RIA). There was an acute release of PGFM in response to ethanol comparing to other treatments (p , 0.05). However, only cows treated with PGF2, underwent luteolysis. In the second experiment, endometrial explants of cross-bred beef cows (n = 4) slaughtered at day 17 of the oestrous cycle were cultured for 4 h. During the last 3 h, the explants were cultured with medium supplemented with 0, 0.1, 1, 10 or 100 ,l of 100% ethanol/ml. Medium samples were collected at hours 1 and 4 and concentrations of PGF2, were measured by RIA. Ethanol did not induce PGF2, production by the endometrium. In conclusion, ethanol does not cause luteolysis in cows because it stimulates production of PGF2, in extra-endometrial tissues. [source] Metabolism of dimethylarsinic acid in rats: production of unidentified metabolites in vivoAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2001Kaoru Yoshida Abstract Our previous study revealed that two unidentified metabolites, M-1 and M-2, were excreted in urine after long-term oral administration of dimethylarsinic acid (DMA), the main metabolite of inorganic arsenic. In the present study, we attempted to clarify the mechanism of production of these unknown metabolites. Male F344/DuCrj rats were administered a single dose of DMA (50,mg kg,1) orally or intraperitoneally with or without pretreatment with L -buthionine-SR-sulfoximine (BSO), which inhibits glutathione (GSH) synthesis. Urine was collected by forced urination at various time points after administration of DMA. Arsenic metabolites in urine were analyzed by ion chromatography with inductively coupled plasma mass spectrometry (IC,ICP-MS). The unidentified metabolites M-1 and M-2 were excreted later than elimination of DMA and trimethylarsine oxide (TMAO). GSH depletion decreased in TMAO elimination, suggesting that GSH plays important roles in the methylation of DMA to TMAO in rats. There was no difference in the amount of production of either M-1 or M-2 between BSO-pretreated rats and controls, suggesting that M-1 and M-2 cannot be formed during methylation in the liver. The amounts of elimination of M-1 and M-2 were less after intraperitoneal administration than after oral administration. Male F344/DuCrj rats were given 100,mg As l,1 DMA via drinking water for 20 weeks. Urine and feces were collected forcibly and were analyzed by IC,ICP-MS. A new unidentified metabolite, M-3, was detected only in feces as a metabolite of DMA after 20 weeks exposure to DMA, although M-1 and M-2 were found in both urine and feces. The unidentified metabolites M-1, M-2, and M-3 were excreted mainly as fecal metabolites along with unmetabolized DMA. This finding also suggests that M-1, M-2, and M-3 might be produced in the intestinal tract. Copyright © 2001 John Wiley & Sons, Ltd. [source] Potential antioxidant activity of celecoxib and amtolmetin guacyl: in vitro studiesAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 1 2007M. Kirkova Summary 1,In vitro studies of the potential antioxidant activity of the selective cyclo-oxygenase-2 inhibitor celecoxib and the non-steroid anti-inflammatory drug amtolmetin guacyl (AMG) were carried out. The study included experiments on the ability of these drugs to affect some indices of the oxidative stress [lipid peroxidation (LP), activity of antioxidant enzymes, glutathione (GSH) level] in rat stomach and colon mucosa and in liver. 2,Celecoxib and AMG did not change the activity of the enzymes GSH-peroxidase, oxidased glutathione (GSSG)-reductase and glucose-6-phosphate-dehydrogenase, as well as the GSH level in all tissue preparations. An increased superoxide dismutase (SOD) activity and a tendency to a decreased Fe/ascorbic acid-induced LP in stomach and colon mucosa were found, but only in the presence of AMG. 3,In the liver, both celecoxib and AMG decreased spontaneous and Fe/ascorbic acid-induced LP. SOD activity was enhanced only in the presence of AMG. 4,Experiments aimed at studying celecoxib and AMG in free oxygen radical-generating systems were also carried out. AMG and tolmetin (the main metabolite of AMG) inhibited OH, -provoked deoxyribose degradation in a Fenton system. Celecoxib had no effect on free radicals when tested in the same system. 5,In conclusion, the results of the present in vitro studies suggest that AMG and celecoxib possess antioxidant and metal-chelating abilities, which might contribute to their beneficial effects. [source] Determination of imatinib mesylate and its main metabolite (CGP74588) in human plasma and murine specimens by ion-pairing reversed-phase high-performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 7 2007Roos L. Oostendorp Abstract A sensitive reversed-phase high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of imatinib, a tyrosine kinase inhibitor, and its main metabolite N -desmethyl-imatinib (CGP74588) in human plasma and relevant murine biological matrices. A simple HPLC assay for the individual quantification of imatinib and CGP74588 in murine specimens has not been reported to date. Sample pre-treatment involved liquid,liquid extraction with tert -butyl-methyl ether. Imatinib, CGP74588 (metabolite) and the internal standard 4-hydroxybenzophenone were separated using a narrow bore (2.1 × 150 mm) stainless steel Symmetry C18 column and detected by UV at 265 nm. The mobile phase consisted of 28% (v/v) acetonitrile in 50 mm ammonium acetate buffer pH 6.8 containing 0.005 m 1-octane sulfonic acid and was delivered at 0.2 mL/min. The calibration curve was prepared in blank human plasma and was linear over the dynamic range 10 ng/mL to 10 µg/mL). The accuracy was close to 100% and the within-day and between-day precisions were within the generally accepted 15% range. The validation results showed that the assay was selective and reproducible. This method was applied to study the pharmacokinetics of imatinib and its main metabolite in human and mice. Copyright © 2007 John Wiley & Sons, Ltd. [source] Pharmacokinetic interaction study between eslicarbazepine acetate and lamotrigine in healthy subjectsACTA NEUROLOGICA SCANDINAVICA, Issue 4 2010L. Almeida Almeida L, Nunes T, Sicard E, Rocha J-F, Falcăo A, Brunet J-S, Lefebvre M, Soares-da-Silva P. Pharmacokinetic interaction study between eslicarbazepine acetate and lamotrigine in healthy subjects. Acta Neurol Scand: 2010: 121: 257,264. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objective,,, Anti-epileptic drugs are often used in combination. Both eslicarbazepine (main metabolite of eslicarbazepine acetate, ESL) and lamotrigine undergo conjugation with glucuronic acid, and both eslicarbazepine and its glucuronide and lamotrigine glucuronide undergo extensive renal elimination; therefore, there is a potential for interaction. This study investigated the interaction between ESL and lamotrigine in healthy subjects. Methods,,, Open-label study in two parallel groups of 16 healthy volunteers each. After an 8-day treatment with ESL or lamotrigine, ESL (1200 mg once-daily) and lamotrigine (150 mg once-daily) were co-administered for 19 days. Geometric mean ratios (GMR) and 90% confidence intervals (90% CI) for maximum plasma concentration (Cmax) and area under the plasma concentration,time curve in the dosing interval (AUC0,24) were calculated for eslicarbazepine (ESL active metabolite) and lamotrigine. Results,,, The Cmax and AUC0,24 GMR (90% CI) were, respectively, 95% (87,102%) and 96% (91,102%) for eslicarbazepine, and 88% (82,94%) and 86% (81,92%) for lamotrigine. The 90% CI of the Cmax and AUC0,24 GMR fell within the prespecified acceptance interval (80,125%) both for eslicarbazepine and lamotrigine. Conclusion,,, There was no significant pharmacokinetic interaction between ESL and lamotrigine in healthy subjects. Therefore, no dosage adjustment appears to be usually required in either lamotrigine or ESL when the drugs are co-administered. [source] Simple method for determination of cocaine and main metabolites in urine by CE coupled to MSELECTROPHORESIS, Issue 12 2009José Luiz da Costa Abstract In this work, a simple method for the simultaneous determination of cocaine (COC) and five COC metabolites (benzoylecgonine, cocaethylene (CET), anhydroecgonine, anhydroecgonine methyl ester and ecgonine methyl ester) in human urine using CE coupled to MS via electrospray ionization (CE-ESI-MS) was developed and validated. Formic acid at 1,mol/L concentration was used as electrolyte whereas formic acid at 0.05,mol/L concentration in 1:1 methanol:water composed the coaxial sheath liquid at the ESI nozzle. The developed method presented good linearity in the dynamic range from 250,ng/mL to 5000,ng/mL (coefficient of determination greater than 0.98 for all compounds). LODs (signal-to-noise ratio of 3) were 100,ng/mL for COC and CET and 250,ng/mL for the other studied metabolites whereas LOQ's (signal-to-noise ratio of 10) were 250,ng/mL for COC and CET and 500,ng/mL for all other compounds. Intra-day precision and recovery tests estimated at three different concentration levels (500, 1500 and 5000,ng/mL) provided RSD lower than 10% (except anhydroecgonine, 18% RSD) and recoveries from 83,109% for all analytes. The method was successfully applied to real cases. For the positive urine samples, the presence of COC and its metabolites was further confirmed by MS/MS experiments. [source] Enantioseparation of warfarin and its metabolites by capillary zone electrophoresisELECTROPHORESIS, Issue 15 2003Qingyu Zhou Abstract A capillary zone electrophoresis (CZE) method with direct ultraviolet (UV)-absorbance detection is presented for the simultaneous enantiomeric separation of warfarin and its main metabolites, including warfarin alcohols, 4'-, 6-, and 7-hydroxywarfarin, using highly sulfated ,-cyclodextrin (HS-,-CD) as the chiral selector. This chiral separation method was optimized in terms of the electrophoretic parameters, which included the concentration of HS-,-CD used, the type and composition of organic modifier added to the background electrolyte (BGE) buffer, and the BGE buffer pH. Chiral separation of warfarin and its major metabolites was achieved with high resolution, selectivity, efficiency, repeatability, and reproducibility. This optimized chiral analysis of warfarin along with its metabolites was completed within a satisfactory electrophoresis time of 20 min. [source] Discrepancy between acute and chronic toxicity induced by imidacloprid and its metabolites in Apis melliferaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2001Séverine Suchail Abstract Imidaclopridi a systemic nitroguanidine insecticide that belongs to theneonicotinoid family. As an agonist of the acetylcholine receptor, it attacks the insect nervous system and is extremely effective against various sucking and mining pests. Oral acute and chronic toxicity of imidacloprid and its main metabolites (5-hydroxyimidacloprid, 4,5-dihydroxyimidacloprid, desnitroimidacloprid, 6-chloronicotinic acid, olefin, and urea derivative) were investigated in Apis mellifera. Acute intoxication by imidacloprid or its metabolites resulted in the rapid appearance of neurotoxicity symptoms, such as hyperresponsiveness, hyperactivity, and trembling and led to hyporesponsiveness and hypoactivity. For acute toxicity tests, bees were treated with doses of toxic compounds ranging from 1 to 1,000 ng/bee (10,10,000 ,g/kg). Acute toxicity (LD50) values of imidacloprid were about 60 ng/bee (600 ,g/kg) at 48 h and about 40 ng/bee (400 ,g/kg) at 72 and 96 h. Out of the six imidacloprid metabolites tested, only two (5-hydroxyimidacloprid and olefin) exhibited a toxicity close to that of imidacloprid. Olefin LD50 values were lower than those of imidacloprid. The 5-hydroxyimidacloprid showed a lower toxicity than imidacloprid with a LD50 four to six times higher than that of imidacloprid. Urea also appeared as a compound of nonnegligible toxicity by eliciting close to 40% mortality at 1,000 ng/bee (10,000 ,g/kg). However, no significant toxicity was observed with 4,5-dihydroxyimidacloprid, 6-chloronicotinic acid, and desnitroimidacloprid in the range of doses tested. To test chronic toxicity, worker bees were fed sucrose solutions containing 0.1, 1, and 10 ,g/L of imidacloprid and its metabolites for 10 d. Fifty percent mortality was reached at approximately 8 d. Hence, considering that sucrose syrup was consumed at the mean rate of 12 ,l/d and per bee, after an 8-d period the cumulated doses were approximately 0.01, 0.1, and 1 ng/bee (0.1, 1, and 10 ,g/kg). Thus, all tested compounds were toxic at doses 30 to 3,000 (olefin), 60 to 6,000 (imidacloprid), 200 to 20,000 (5-OH-imidacloprid), and >1,000 to 100,000 (remaining metabolites) times lower than those required to produce the same effect in acute intoxication studies. For all products tested, bee mortality was induced only 72 h after the onset of intoxication. [source] Studies on the metabolism of the ,9-tetrahydrocannabinol precursor ,9-tetrahydrocannabinolic acid A (,9-THCA-A) in rat using LC-MS/MS, LC-QTOF MS and GC-MS techniquesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2009Julia Jung Abstract In Cannabis sativa, ,9-Tetrahydrocannabinolic acid-A (,9-THCA-A) is the non-psychoactive precursor of ,9-tetrahydrocannabinol (,9-THC). In fresh plant material, about 90% of the total ,9-THC is available as ,9-THCA-A. When heated (smoked or baked), ,9-THCA-A is only partially converted to ,9-THC and therefore, ,9-THCA-A can be detected in serum and urine of cannabis consumers. The aim of the presented study was to identify the metabolites of ,9-THCA-A and to examine particularly whether oral intake of ,9-THCA-A leads to in vivo formation of ,9-THC in a rat model. After oral application of pure ,9-THCA-A to rats (15 mg/kg body mass), urine samples were collected and metabolites were isolated and identified by liquid chromatography-mass spectrometry (LC-MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high resolution LC-MS using time of flight-mass spectrometry (TOF-MS) for accurate mass measurement. For detection of ,9-THC and its metabolites, urine extracts were analyzed by gas chromatography-mass spectrometry (GC-MS). The identified metabolites show that ,9-THCA-A undergoes a hydroxylation in position 11 to 11-hydroxy-,9-tetrahydrocannabinolic acid-A (11-OH-,9-THCA-A), which is further oxidized via the intermediate aldehyde 11-oxo-,9-THCA-A to 11-nor-9-carboxy-,9-tetrahydrocannabinolic acid-A (,9-THCA-A-COOH). Glucuronides of the parent compound and both main metabolites were identified in the rat urine as well. Furthermore, ,9-THCA-A undergoes hydroxylation in position 8 to 8-alpha- and 8-beta-hydroxy-,9-tetrahydrocannabinolic acid-A, respectively, (8,-Hydroxy-,9-THCA-A and 8,-Hydroxy-,9-THCA-A, respectively) followed by dehydration. Both monohydroxylated metabolites were further oxidized to their bishydroxylated forms. Several glucuronidation conjugates of these metabolites were identified. In vivo conversion of ,9-THCA-A to ,9-THC was not observed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Development and validation of a liquid chromatographic/electrospray ionization mass spectrometric method for the quantitation of prazepam and its main metabolites in human plasmaJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2005Paraskevi Valavani Abstract A method was developed and fully validated for the quantitation of prazepam and its major metabolites, oxazepam and nordiazepam, in human plasma. Sample pretreatment was achieved by solid-phase extraction using Oasis HLB cartridges. The extracts were analysed by high-performance liquid chromatography (HPLC) coupled with single-quadrupole mass spectrometry (MS) with an electrospray ionization interface. The MS system was operated in the selected ion monitoring mode. HPLC was performed isocratically on a reversed-phase XTerra MS C18 analytical column (150 × 3.0 mm i.d., particle size 5 µm). Diazepam was used as the internal standard for quantitation. The assay was linear over a concentration range of 5.0,1000 ng ml,1 for all compounds analyzed. The limit of quantitation was 5 ng ml,1 for all compounds. Quality control samples (5, 10, 300 and 1000 ng ml,1) in five replicates from three different runs of analysis demonstrated an intra-assay precision (CV) of ,9.1%, an inter-assay precision of ,6.0% and an overall accuracy (relative error) of <4.6%. The method can be used to quantify prazepam and its metabolites in human plasma covering a variety of pharmacokinetic or bioequivalence studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Cyamemazine metabolites: effects on human cardiac ion channels in-vitro and on the QTc interval in guinea pigsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 11 2008William Crumb Monodesmethyl cyamemazine and cyamemazine sulfoxide, the two main metabolites of the antipsychotic and anxiolytic phenothiazine cyamemazine, were investigated for their effects on the human ether-ŕ-go-go related gene (hERG) channel expressed in HEK 293 cells and on native INa, ICa, Ito, Isus or IK1 of human atrial myocytes. Additionally, cyamemazine metabolites were compared with terfenadine for their effects on the QT interval in anaesthetized guinea pigs. Monodesmethyl cyamemazine and cyamemazine sulfoxide reduced hERG current amplitude, with IC50 values of 0.70 and 1.53 ,M, respectively. By contrast, at a concentration of 1 ,M, cyamemazine metabolites failed to significantly affect INa, Ito, Isus or IK1 current amplitudes. Cyamemazine sulfoxide had no effect on ICa at 1 ,M, while at this concentration, monodesmethyl cyamemazine only slightly (17%), albeit significantly, inhibited ICa current. Finally, cyamemazine metabolites (5 mg kg,1 i.v.) were unable to significantly prolong QTc values in the guinea pig. Conversely, terfenadine (5 mg kg,1 i.v.) significantly increased QTc values. In conclusion, cyamemazine metabolite concentrations required to inhibit hERG current substantially exceed those necessary to achieve therapeutic activity of the parent compound in humans. Moreover, cyamemazine metabolites, in contrast to terfenadine, do not delay cardiac repolarization in the anaesthetized guinea pig. These non-clinical findings explain the excellent cardiac safety records of cyamemazine during its 30 years of extensive therapeutic use. [source] Enantiomeric separation of mirtazapine and its metabolites by nano-liquid chromatography with UV-absorption and mass spectrometric detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2005Salvatore Fanali Abstract Mirtazapine (MIR) and two of its main metabolites, namely, 8-hydroxymirtazapine and N -desmethylmirtazapine, were separated in totheir enantiomers by nanoLC in a laboratory-made fused-silica capillary column (75 ,m ID) packed with a vancomycin-modified silica stationary phase. The simultaneous separation of the three couples of the studied enantiomers was achieved in less than 33 min, using an experimentally optimized mobile phase delivered in the isocratic mode. Optimization of the mobile-phase composition was achieved by testing the influence of the buffer pH and concentration, the water concentration, the organic modifier type and concentration, and on the retention and resolution of the analytes. The optimum mobile-phase composition contained 500 mM ammonium acetate pH 4.5/water/MeOH/MeCN, 1 : 14 : 40 : 45 v/v/v/v. Using a UV detector at 205 nm, the method was validated studying several experimental parameters such as LOD and LOQ, intraday and interday repeatability, and linearity. Good results were achieved: LOD and LOQ were in the range 5,15 and 10,40 ,g/mL, respectively (the highest value was obtained for the DEMIR enantiomers); correlation coefficients, 0.9993,0.9999; the intraday and interday precision was acceptable (RSD < 2%) using an internal standard. The method was tested for the separation of the studied enantiomers in an extracted (solid-phase) serum sample spiked with standard racemic mixture of MIR and its two metabolites. Finally, the nanoLC system was connected to a mass spectrometer through a nanoelectrospray interface and the MS, MS2, and MS3 spectra were acquired showing the potential of the system used for characterization and identification of the separated analytes. [source] Pharmacokinetics of flubendazole and its metabolites in lambs and adult sheep (Ovis aries)JOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2009Flubendazole (FLU) is indicated for control of helminthoses in pig and avian species (monogastric animals) and its corresponding pharmacokinetics are well known. The information on FLU's pharmacokinetic behavior in animal species with forestomach (ruminants) has been limited although the use of FLU in these species could be beneficial. The aim of this study was to investigate the pharmacokinetics of FLU and its main metabolites in sheep. The effects of animal age (sexually immature and mature ones) and gender were also studied. FLU was orally administered in a single experimental dose (30 mg/kg of body weight) in the form of oral suspension. Treated immature animals (aged 3 months) and 5 months later the same mature individuals (aged 8 months) were kept under the same conditions (food, water and management) and treated with FLU. Within 72 h after FLU administration, plasmatic samples were collected and FLU and its Phase I metabolites were quantified using high-performance liquid chromatography. FLU was detected in very low concentrations only, reduced FLU (FLU-R) was identified as the main metabolite, and hydrolyzed FLU (FLU-H) as the minor one. Formation of FLU-R was stereospecific with (+)-FLU-R domination. The plasmatic concentrations of (+)-FLU-R reached 10,15 times higher values than those of FLU, (,)-FLU-R and FLU-H. A significant gender effect on pharmacokinetics of FLU or (+)-FLU-R metabolite in the mature animals was found and a wide significant difference between lambs and adult sheep in FLU including both metabolites has been proved. [source] Characterization of oligodendrogliomas using short echo time 1H MR spectroscopic imagingNMR IN BIOMEDICINE, Issue 1 2003M. Rijpkema Abstract Oligodendroglial tumors may not be distinguished easily from other brain tumors based on clinical presentation and magnetic resonance imaging (MRI) alone. Identification of these tumors however may have therapeutic consequences. The purpose of this study was to characterize and identify oligodendrogliomas by their metabolic profile as measured by 1H MR spectroscopic imaging (MRSI). Fifteen patients with oligodendroglial tumors (eight high-grade oligodendrogliomas, seven low-grade oligodendrogliomas) underwent MRI and short echo time 1H MRSI examinations. Five main metabolites found in brain MR spectra were quantified and expressed as ratios of tumor to contralateral white matter tissue. The level of lipids plus lactate was also assessed in the tumor. For comparison six patients with a low grade astrocytoma were also included in the study. The metabolic profile of oligodendrogliomas showed a decreased level of N -acetylaspartate and increased levels of choline-containing compounds and glutamine plus glutamate compared with white matter. The level of glutamine plus glutamate was significantly higher in low-grade oligodendrogliomas than in low-grade astrocytomas and may serve as a metabolic marker in diagnosis and treatment planning. In high-grade oligodendrogliomas large resonances of lipids plus lactate were observed in contrast to low-grade tumors. Copyright © 2003 John Wiley & Sons, Ltd. [source] Metabolism of fungicidal cyanooximes, cymoxanil and analogues in various strains of Botrytis cinereaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2009Frédérique Tellier Abstract BACKGROUND: The metabolism of cymoxanil [1-(2-cyano-2-methoxyiminoacetyl)-3-ethylurea] and fungicidal cyanooxime analogues was monitored on three phenotypes of Botrytis cinerea Pers. ex Fr. differing in their sensitivity towards cymoxanil. For this purpose, labelled [2- 14C]cymoxanil was added either to the culture medium of these strains or to its cell-free extract. RESULTS: In the culture medium of the most sensitive strain, four main metabolites were detected. Three were isolated and identified. Cymoxanil was quickly metabolised by at least three concurrent enzymatic pathways: (i) cyclisation leading, after hydrolysis, to ethylparabanic acid, (ii) reduction giving demethoxylated cymoxanil, (iii) hydrolysis followed by reduction and then acetylation leading to N -acetylcyanoglycine. In the cell-free extract of the same strain, only the first and the second of these enzymatic reactions occurred. By comparing the metabolic profile of the most sensitive strain with that of the less sensitive ones, it was shown that the decrease in sensitivity to cymoxanil correlates with a reduced acetylcyanoglycine formation. Among all metabolites, only N -acetylcyanoglycine is active against the most sensitive strain. Moreover, in a culture of this strain, two other fungicidal cyanooximes were also metabolised into this metabolite. CONCLUSION: The formation of N -acetylcyanoglycine may play an important role in the fungitoxicity of cymoxanil and cyanooxime derivatives. Copyright © 2008 Society of Chemical Industry [source] In vivo distribution and metabolisation of 14C-imidacloprid in different compartments of Apis mellifera LPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2004Séverine Suchail Abstract In vivo distribution of the neonicotinoid insecticide, imidacloprid, was followed during 72 h in six biological compartments of Apis mellifera L: head, thorax, abdomen, haemolymph, midgut and rectum. Honeybees were treated orally with 100 µg of 14C-imidacloprid per kg of bee, a dose close to the median lethal dose. Elimination half-life of total radioactivity in honeybee was 25 h. Haemolymph was the compartment with the lowest and rectum that with the highest level of total radioactivity during the whole study, with a maximum 24 h after treatment. Elimination half-life of imidacloprid in whole honeybee was 5 h. Imidacloprid was readily distributed and metabolised only by Phase I enzymes into five metabolites: 4/5-hydroxy-imidacloprid, 4,5-dihydroxy-imidacloprid, 6-chloronicotinic acid, and olefin and urea derivatives. The guanidine derivative was not detected. The urea derivative and 6-chloronicotinic acid were the main metabolites and appeared particularly in midgut and rectum. The olefin derivative and 4/5-hydroxy-imidacloprid preferentially occurred in head, thorax and abdomen, which are nicotinic acetylcholine receptor-rich tissues. Moreover, they presented a peak value around 4 h after imidacloprid ingestion. These results explain the prolongation of imidacloprid action in bees, and particularly the differences between rapid intoxication symptoms and late mortality. Copyright © 2004 Society of Chemical Industry [source] Toxicological determination and in vitro metabolism of the designer drug methylenedioxypyrovalerone (MPDV) by gas chromatography/mass spectrometry and liquid chromatography/quadrupole time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2010Sabina Strano-Rossi A method for the toxicological screening of the new designer drug methylenedioxypyrovalerone (MDPV) is described; with an emphasis on its application for anti-doping analysis. The metabolism of MDPV was evaluated in vitro using human liver microsomes and S9 cellular fractions for CYP450 phase I and uridine 5,-diphosphoglucuronosyltransferase (UGT) and sulfotransferase (SULT) phase II metabolism studies. The resulting metabolites were subsequently liquid/liquid extracted and analyzed using gas chromatography/mass spectrometry (GC/MS) as trimethylsilyl (TMS) derivatives. The structures of the metabolites were further confirmed by accurate mass measurement using a liquid chromatography/quadrupole time-of-flight (LC/QTOF) mass spectrometer. The studies demonstrated that the main metabolites of MDPV are catechol and methyl catechol pyrovalerone, which are in turn sulfated and glucuronated. The method for the determination of MDPV in urine has been fully validated by assessing the limits of detection and quantification, linearity, repeatability, and accuracy. This validation demonstrates the suitability for screening of this stimulant substance for anti-doping and forensic toxicology purposes. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||