Search results for " High pressure liquid"
showing 10 items of 705 documents
Effects of the benzodiazepine receptor agonist midazolam and antagonist flumazenil on 5-hydroxytryptamine release from guinea-pig intestine in vitro
1990
Isolated segments of the guinea-pig small intestine and the guinea-pig stomach were vascularly perfused and the release of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid into the portal venous effluent determined by high pressure liquid chromatography with electrochemical detection. Test substances were applied intraarterially. The benzodiazepine receptor agonist, midazolam, concentration-dependently increased (by 58%, at 1 nmol/l) and decreased (by 32%, at 100 nmol/l) the release of 5-HT from small intestine preparations. Both effects were blocked by the benzodiazepine receptor antagonist flumazenil (10 nmol/l) The stimulatory effect of midazolam was also abolished in the presen…
An evaluation of solid phase microextraction for aliphatic amines using derivatization with 9-fluorenylmethyl chloroformate and liquid chromatography
2005
The reliability of SPME combined with a chemical reaction for the analysis of short-chain aliphatic amines by liquid chromatography has been investigated. Different options to couple SPME and derivatization have been tested and compared: (i) derivatization of the analytes in solution followed by the extraction of the derivatives, (ii) extraction of the analytes and subsequent derivatization by immersing the SPME fibre onto a solution of the reagent, and (iii) extraction/derivatization of the analytes using fibres previously coated with the reagent. Methylamine (MA), dimethylamine (DMA) and trimethylamine (TMA) have been selected as a model of primary, secondary and tertiary amines, respecti…
Improved automated synthesis of [18F]fluoroethylcholine as a radiotracer for cancer imaging.
2007
[(18)F]Fluoroethylcholine has been recently introduced as a promising (18)F-labelled analogue of [(11)C]choline which had been previously described as a tracer for metabolic cancer imaging with positron emission tomography (PET). Due to the practical advantages of using the longer-lived radioisotope (18)F (t(1/2)=110 min), offering the opportunity of a more widespread clinical application, we established a reliable, fully automated synthesis for its production using a modified, commercially available module. [(18)F]Fluoroethylcholine was prepared from N,N-dimethylaminoethanol by iodide catalyzed alkylation with 1-[(18)F]fluoro-2-tosylethane as alkylating agent, resulting in a total radioche…
Study of chemical changes produced in virgin olive oils with different phenolic contents during an accelerated storage treatment.
2009
Chemical changes produced in an extra virgin olive oil sample in the presence (EVOO) and absence (EVOOP) of its phenolic fraction during an accelerated storage treatment at 60 degrees C up to 7 weeks were studied. Modifications in phenol content, as well as changes in several quality parameters (free acidity, peroxide value, UV absorbance, fatty acid composition, oxidative stability index, and tocopherol content) were also evaluated under the same storage conditions and compared to those of the same sample deprived of phenolic compounds. When the phenolic extract of the EVOO was studied, a decrease of the antioxidants first present in the sample and an increase of the oxidized products were…
Studies on pathways of ring opening of benzene in a Fenton system
1995
Ring-opened products of benzene metabolism have been postulated to play a role in hematotoxicity and leukemogenesis. The reaction of benzene in the Fenton system was reexamined to determine the presence of compounds which might serve as intermediates in the formation of trans, trans-muconaldehyde (MUC), a microsomal hematotoxic metabolite of benzene. Benzene dihydrodiol (DHD) was found in this system based on coelution with authentic standard, ultraviolet (UV) absorption characteristics, and molecular weight. Incubation of DHD in the Fenton system resulted in the formation of phenol (PH), catechol (CAT), and products which reacted with thiobarbituric acid to form chromogens absorbing at 495…
Biomonitoring of Enniatin B1 and Its Phase I Metabolites in Human Urine: First Large-Scale Study
2020
Enniatins (Enns) are mycotoxins produced by Fusarium spp. which are a fungus widely spread throughout cereals and cereal-based products. Among all the identified enniatins, Enn B1 stands as one of the most prevalent analogues in cereals in Europe. Hence, the aim of this study was to evaluate for the first time the presence of Enn B1 and its phase I metabolites in 300 human urine samples using an ultrahigh-performance liquid chromatography high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) methodology. Enn B1 was detected in 94.3% of samples ranging from 0.007 to 0.429 ng/mL (mean value: 0.065 ng/mL). In accordance with previous in vitro and in vivo analysis, hydroxylated metabolites …
Target Analysis and Retrospective Screening of Multiple Mycotoxins in Pet Food Using UHPLC-Q-Orbitrap HRMS
2019
A comprehensive strategy combining a quantitative method for 28 mycotoxins and a post-target screening for other 245 fungal and bacterial metabolites in dry pet food samples were developed using an acetonitrile-based extraction and an ultrahigh-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) method. The proposed method showed satisfactory validation results according to Commission Decision 2002/657/EC. Average recoveries from 72 to 108% were obtained for all studied mycotoxins, and the intra-/inter-day precision were below 9 and 14%, respectively. Results showed mycotoxin contamination in 99% of pet food samples (n = 89) at concentratio…
Antifungal effects of the bioactive compounds enniatins A, A1, B, B1
2010
To produce enniatin (ENs), Fusarium tricinctum CECT 20150 was grown in a liquid medium of potato (PDB), being mycotoxin purified by high performance liquid chromatography (HPLC) with a reverse phase semipreparative column using a mobile phase of acetonitrile/water using gradient condition. The purity of the ENs fractions was verified by analytical HPLC and LC/MS-MS. The pure fractions of ENs were utilized to study the biological activity on several mycotoxigenic moulds as Fusarium verticilloides, Fusarium sporotrichioides, Fusarium tricinctum, Fusarium poae, Fusarium oxysporum, Fusarium proliferatum, Beauveria bassiana, Trichoderma harzianum, Aspergillus flavus, Aspergillus parasiticus, Asp…
Toxigenic potential of Fusarium culmorum strains isolated from French wheat
2001
Sixty F. culmorum strains were isolated from wheat grains collected from different wheat-growing areas in France and from different cultivars. The isolates were grown on autoclaved wheat grain to assess their ability to produce trichothecenes and zearalenone. Fungal biomass was evaluated through the ergosterol grain content. All the isolates produced zearalenone (0.39-1660 mg kg(-1)). Thirty-five of the 60 F. culmorum produced nivalenol (0.11-11.7 mg kg(-1)), 12 of 60 produced fusarenone X (0.05-8.42 mg kg(-1)), five of 60 produced 15-acetyldeoxynivalenol (0.48-27.7 mg kg(-1)), 13 of 60 produced 3-acetyldeoxynivalenol (0.07-21.0 mg kg(-1) and 24 of 60 produced deoxynivalenol (0.92-51.9 mg k…
Isolation, purification, LC–MS/MS characterization and reactive oxygen species induced by fumonisin B1 in VERO cells
2010
Fumonisins are mycotoxins produced by Fusarium verticillioides that commonly contaminate maize and maize products. The present work shows the results of a comparative study of three different fermentation's techniques (solid and liquid medium of corn and a solid agarized medium) for the production of fumonisins B-1, B-2 and B-3 with strains of F. verticillioides. The solid medium of corn was the most effective in the production of fumonisins, being Fumonisin B-1 the one produced with higher concentration, so the extract obtained by solid fermentation process was used for FB1 purification. Fumonisins characterization and quantification were performed with reversed-phase high-performance liqu…