Search results for "ACID HYDROLYSIS"
showing 10 items of 38 documents
RP-HPLC Determination of Tiger Nut and Orgeat Amino Acid Contents
2005
The amino acid profile of 11 samples of tiger nuts ( Cyperus esculentusL.) grown in the area of “L'Horta Nord” in Valencia (Spain) and one sample of African origin were determined, along with the amino acid contents of 10 samples of natural orgeat from Valencia. Protein was hydrolysed by hydrochloric acid at 110 °C for 23 h, and amino acids were derivatised with AQC and determined by RP-HPLC with fluorescence detection. The chromatographic conditions were optimised. The analytical parameters (detection and quantification limits, precision and accuracy) showed the method to be sufficiently sensitive and reproducible for determining amino acids resistant to acid hydrolysis in tiger nuts and o…
Characterization of totally chlorine-free effluents from Kraft pulp bleaching
1999
A capillary zone electrophoresis (CZE) method for analyzing the total acid hydrolysis products (monosaccharides and their derivatives) of the dissolved carbohydrates from a totally chlorine-free bleaching plant was developed. Several borate buffer concentrations and other running conditions were tested. Neutral monosaccharides (arabinose, galactose, glucose, mannose, rhamnose and xylose) in hydrolysates were derivatized by means of 4-aminobenzonitrile and resolved by 500 mM borate buffer (pH 9.5, 16.0 kV). The detection level was less than 10 fmol. In addition, the separation of some uronic acids and oligosaccharides was studied.
Pretreatment and fractionation of lignocellulosic barley straw by mechanocatalysis
2017
Abstract This study focuses on the mechanocatalytical process combining dilute acid pretreatment and mechanical processing driven by ball milling. Milled and hydrolyzed barley straw samples are subject to reducing sugar analysis by DNS assay and capillary electrophoresis. Optimization of the saccharification conditions was carried out with two different sulfuric acid concentrations, 0.5 mol kg −1 and 1.0 mol kg −1 , and compared. A significant yield of total reducing sugar (53.4%) was obtained from barley straw impregnated with sulfuric acid (1.0 mol kg −1 ) after milling for only 20 min. Glucose and xylose concentrations accounted for 3.5% and 11.3%, respectively. Strikingly, the present s…
Über die Verbreitung von Flavonoiden bei pleurokarpen Laubmoosen I. Apigenin-7-rhamnoglucosid bei Hylocomium splendens (Hedw.) Br. eur.
1977
Summary 15 species of pleurocarpous mosses have been investigated as to their content of flavonoids. Flavonoid tests on 14 species have given negative results. Only one species, Hylocomium splendens , contains one flavonoid. It was purified by means of paper chromatography and is by chromatography and absorption spectrum identical with rhoifolin (apigenin-7-neohesperidoside). Partial acid hydrolysis yields apigenin-7-monoglucoside and rhamnose, quantitative hydrolysis apigenin, rhamnose and glucose. They were identified by comparison with authentic samples.
Über die Verbreitung von Flavonoiden bei pleurokarpen Laubmoosen II. Apigenin and Apigenin-7-rhamnoglucosid bei Pleurozium schreberi (Willd.) Mitt.
1980
Summary 12 species of pleurocarpous mosses have been investigated as to their content of flavonoids. Flavonoid tests on 11 species have given negative results. Only one species, Pleurozium schreberi , contains three flavonoids. They were purified by means of paper chromatography. Two of them are by chromatography, acid hydrolysis and absorption spectrum identical with apigenin and apigenin-7-rhamnoglucoside. The third flavonoid is as yet unidentified. Qualitative hydrolysis yields apigenin. The chemotaxonomic importance of the results is briefly discussed.
Characterization of proteinaceous glues in old paintings by separation of the o-phtalaldehyde derivatives of their amino acids by liquid chromatograp…
2005
A HPLC-fluorescence method for characterization of proteinaceous glues from binding media used in pictorial works of art prior to conservation or restoration treatment is proposed. Fluorescence derivatization of amino acids released by acid hydrolysis of standard proteins is studied. The derivatization reagent was o-phtalaldehyde with 2-mercaptoethanol as catalyst. Mobile phase was a programmed gradient among two eluents (water buffered at pH 5.8 wit 5% THF, and methanol) and is able to satisfactorily resolve the amino acid derivatives in 45min. Peak area ratios among amino acid derivatives and the leucine derivative are useful to characterize the proteins. The method shows good sensitivity…
Nucleophilic substitutions in the isoindole series as a valuable tool to synthesize derivatives with antitumor activity
2011
Abstract A novel synthetic approach to the synthesis of 3-substituted isoindoles through nucleophilic substitution of 3-halo derivatives by charged carbon, and neutral nitrogen, oxygen, and sulfur nucleophiles, assisted by a 1-acyl group, is reported. Aryl-thio-isoindoles, obtained through a direct nucleophilic substitution with sulfur nucleophiles, showed cytotoxic activity, with GI50 values from micromolar to sub-micromolar concentrations, against the total number of cell lines investigated.
Carbohydrates as chiral templates: asymmetric ugi-synthesis of alpha-amino acids using galactosylamines as the chiral matrices
1988
Abstract In the presence of Lewis acid catalysts O-acetyl- (1) and O-pivaloyl- (2) protected β-D-galactopyranosylamines react with aldehydes, isocyanides and carboxylic acids in Ugi-four-component-condensations to give the corresponding N-galactosyl-amino acid amide derivatives 3,5 in almost quantitative yields. Zinc chloride is the most effective Lewis acid catalyst. At 0°C or even at room temperature the (2R,β-D)-diastereomers of the amino acid derivatives 3,5 are formed with high diastereoselectivity. If the sterically more demanding O-pivaloyl galactosylamine 2 is used at -78°C to -25°C the stereoselectivity often exeeds 20:1 favouring the (2R,β-D) diastereomers 5. After one recrystalli…
Ursane-Type Triterpene Saponins fromZygophyllum geslini
2007
Four new ursane-based triterpene glycosides, compounds 1–4, as well as the known glycosides zygophylosides E, G, and H, and 3-O-(β-D-quinovopyranosyl)quinovic acid 28-(O-β-D-glucopyranosyl) ester, were isolated from the BuOH-soluble fraction of the MeOH/H2O 7 : 3 extracts of Zygophyllum geslini (roots or aerial parts). Their structures were established mainly by 1D- and 2D-NMR techniques, in combination with HR-MS analysis and acid hydrolysis.
A novel synthesis of 2-aryl-4-piperidones by mannich cyclization of iminoketals
1983
2-Aryl-4-piperidones have been synthesized by condensation between an aromatic aldehyde and a β-aminoketone ethylene ketal, and further cyclization of the resulting iminoketal with dry hydrogen chloride or anhydrous p-toluensulfonic acid. Alternatively, reaction of the above iminoketals with methyl fluorosulfonate followed by dry hydrogen chloride treatment and acid hydrolysis gives directly N-methyl-4-piperidones. The application of these reactions to the synthesis of some 2-aryl-3-acetylpyrrolidine systems is also described.