Search results for "Analytical"
showing 10 items of 9586 documents
Cytotoxicity of an unprecedented brominated oleanolide and a new furoceramide from the Cameroonian spice, Echinops giganteus
2016
A preliminary study on Echinops giganteus (Asteraceae) showed that the methanolic extract has interesting cytotoxicities against a panel of cancer cell lines. From this extract, a lignan, a flavonoid and a polyacetylenic thiophene identified were three times less cytotoxic than the extract. In the search of the metabolites responsible for the bioactivity, a new harvested E. giganteus was subjected to a phytochemical study using chromatographic methods. In the course of the work, two new compounds: a brominated oleanolide (1) and a tetrahydrofurano-ceramide (2) were obtained along with β-amyrin acetate (3), 2-(penta-1,3-diynyl)-5-(4-hydroxybut-1-ynyl)-thiophene (4), 2-(penta-1,3-diynyl)-5-(3…
Lauroyl peroxide as thermal initiator of lauryl methacrylate monolithic columns for CEC
2008
The preparation of lauryl methacrylate (LMA)-based monolithic columns for CEC using lauroyl peroxide (LPO) as thermal initiator of polymerization has been investigated. The influence of initiator amount and composition of porogenic solvent on the physical and electrochromatographic properties of the resulting LMA-based monoliths was evaluated. A comparison with LMA-based columns thermally polymerized with AIBN was performed. At a given porogenic solvent composition, LMA stationary phases initiated with LPO showed higher permeabilities and better efficiency values than those prepared using AIBN as initiator. The optimum polymerization mixture found for LPO initiator provided a minimum plate …
Structure of a polysaccharide from the lipopolysaccharide of Vibrio vulnificus clinical isolate YJ016 containing 2-acetimidoylamino-2-deoxy-L-galactu…
2009
Abstract A polysaccharide isolated after mild acid degradation of the lipopolysaccharide of Vibrio vulnificus clinical isolate YJ016 was found to contain l -Fuc, d -GlcpNAc, 2,4-diacetamido-2,4,6-trideoxy- d -glucose (di-N-acetylbacillosamine, d -QuiNAc4NAc), and 2-acetimidoylamino-2-deoxy- l -galacturonic acid ( l -GalNAmA). The last sugar derivative was confirmed by correlations for nitrogen-linked protons in 2D TOCSY and ROESY spectra measured in a H2O–D2O mixture. The following structure of the polysaccharide was established by 1H and 13C NMR spectroscopy, including 2D ROESY and 1H,13C HMBC experiments: Download : Download full-size image where the degree of 6-O-acetylation of the later…
Occurrence of glycine in the core oligosaccharides of Hafnia alvei lipopolysaccharides--identification of disubstituted glycoform.
2015
Endotoxins (lipopolysaccharides, LPS) are the main surface antigens and virulence factors of Gram-negative bacteria involved for example in the development of nosocomial infections and sepsis. They consist of three main regions: O-specific polysaccharide, core oligosaccharide, and lipid A. Bacteria modify LPS structure to escape the immune defence, but also to adapt to environmental conditions. LPS's structures are highly diversified in the O-specific polysaccharide region to evade bactericidal factors of immune system, but retain some common epitopes that are potential candidates for therapeutic strategies against bacterial infections. Common occurrence of glycine within the structure of L…
New high-performance liquid chromatography-based methodology for monitoring the conformational transitions of self-associating hydrophobic peptides, …
1988
A new high-performance size-exclusion chromatographic strategy is reported for the analysis of the hydrophobic self-associating peptide gramicidin A, incorporated into artificial phospholipid vesicles (liposomes). The method is based on the direct injection of a few microlitres of the gramicidin A-containing liposome suspension into the column, which is eluted with a non-polar solvent, such as tetrahydrofuran. The type and amount of information which can be derived from this methodology have been evaluated. Using this chromatographic approach, a correlation has been unambiguously shown to exist between the organization of the peptide in the vesicles and a number of variables involved in the…
Macromolecules in ordered media. II. A fluorescence study of the polymer-liposome association
1995
The interactions of poly (4-vinyl pyridine) with dimyristoylphosphatidic acid-based liposomes were studied in heterogeneous solution systems. The polymer was dispersed in aqueous buffer solutions of small unilamellar vesicles and after a suitable period of incubation to raise the equilibrium, the experiments has been conducted as a function of polymer concentration and temperature. According to the measurements of the steady-state fluorescence spectra, changes in the intensities as well as shifts in the emission peak wavelength, has served as raw data to accounting for the polymer-vesicle interactions. Quantitative evaluation of the interaction has been done using a simple associating model…
Effect of phosphatydylcholine on spectral properties and photostability of 3,3′-diethyloxadicarbocyanine iodide (DODCI) — a potent anti-tumor photose…
1998
Abstract The potential anti-tumor photosensitizer 3,3′-diethyloxadicarbocyanine iodide (DODCI) has been immobilized in dimyristoyl phosphatidylcholine (DMPC) vesicles. Binding of the dicarbocyanine to the lipid vesicles induces several changes in the electronic absorption, emission and excitation spectra of the dye. The monomeric dye molecules exist in at least two forms when immobilized in the DMPC liposomes and the non-luminescing H-aggregates of the dye show efficient excitation energy transfer to the DODCI monomers. Entrapment of the dye in the liposomes generally decreases the photostability of DODCI. While emission from singlet oxygen (1O2) has not been recorded, indirect results sugg…
Fluidity of liposome membranes doped with organic tin compounds: ESR study.
2008
The kinetics of change in the fluidity of liposome membranes, obtained in the process of sonication of Egg Yolk Lecithin (EYL), with the admixture of organic tin compounds, was investigated. Five compounds were selected for the research: three differed in the length of hydrocarbon chains, (CH(3))(4)Sn, (C(2)H(5))(4)Sn, and (C(3)H(7))(3)SnCl, whereas two differed in the number of aromatic rings, (C(6)H(5))(2)SnCl(2) and (C(6)H(5))(3)SnCl. The concentration of the compounds in proportion to EYL was 2 mol-%. Electron Spin (paramagnetic) Resonance (ESR) was applied using two spin probes TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and 16-DOXYL-stearic acid methyl ester (2-ethyl-2-(15-methoxy-15…
Eliciting callus culture for production of hepatoprotective flavonoids and phenolics from Sequoia sempervirens (D. Don Endl)
2020
The aim of our study is to estimate the hepatoprotective effects of the ethanolic extract of the leaves of Sequoia sempervirens by determination of liver biomarkers (ALT, AST, total bilirubin and albumin in serum) and by histopathological examinations using thioacetamide-induced (TAA) liver injury model. Concurrent administration of ethanolic extracts of S. sempervirens leaves improved the alterations in liver morphology where it was a potent protector of the liver. The potential of L-phenylalanine and silver nitrate as chemical elicitors as well as UV radiation as a physical elicitor on flavonoid production in callus culture of S. sempervirens were emphasized. Murashige and Skoog’s medium …
Determination of major carotenoids in vegetables by capillary electrochromatography.
2006
A simple and rapid method for the isocratic separation and determination of carotenoids (carotenes and xanthophylls) in vegetables by CEC is described. The capillary column (100 microm ID, 25 cm effective length) was packed with 3 microm Hypersil ODS particles. The optimized mobile phase contained 60% ACN, 35% THF and 5% of a 5 mM Tris aqueous buffer of pH 8. beta-Carotene, lycopene and lutein were separated with efficiencies of 66 000-128 000 plates/m within a short time (less than 12 min for the last peak eluted, 13/13'-cis-beta-carotene). An excellent resolution of the three carotenoids, as well as partial resolution of their geometrical isomers, was achieved. Application to the determin…