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At least 1,747 records · Page 97Linked to original sources
PubMed1988

Effects of basic drugs on the hepatic transport of cardiac glycosides in rats.

The effects of some basic and acidic drugs on the hepatic uptake of digoxin and ouabain were studied in isolated rat hepatocytes. Digoxin accumulated against a concentration gradient, and its initial uptake was energy- and temperature-dependent. Digoxin competitively inhibited the uptake of ouabain (Ki = 1.3 microM), which was reported to be transported by a carrier-mediated active transport system. All basic drugs tested (verapamil, dipyridamole, amiodarone, nifedipine, diltiazem, ajmaline, chlorpromazine, imipramine, disopyramide, quinidine, procainamide, propranolol and lidocaine: 50 microM) except for procainamide, propranolol and lidocaine significantly (P less than 0.05) reduced the uptake of digoxin, whereas acidic drugs (salicylic acid and phenytoin) had no effect. The same inhibitory effects were observed for ouabain uptake, whereas the uptake of alanine was not changed by these drugs. Quinidine inhibited the uptake of ouabain in a noncompetitive manner (Ki = 88 microM). These basic drugs had no effect on the permeability of the cells assessed by the trypan blue exclusion test and succinate-simulated oxygen consumption. But carbonylcyanide-m-chlorophenyl hydrazone-stimulated oxygen consumption decreased in the presence of some basic drugs and correlated with their inhibitory effects on digoxin uptake. Therefore, one of the mechanisms of the inhibitory effects of these drugs on digoxin uptake was the inhibition of oxidative phosphorylation. These basic drugs had no effect on the microtubular system, which was assessed by the measurement of tubulin polymerization and colchicine binding to tubulin. The results of our study suggested that many basic drugs have a potential to inhibit the hepatocellular uptake of cardiac glycosides.

Animals↗
PubMed1989

Novel inhibitory actions on platelet thromboxane and inositolphosphate formation by xanthones and their glycosides.

Xanthones and their glycosides were tested for their antiplatelet activities in washed rabbit platelets. Tripteroside acetate and norathyriol acetate were the most potent inhibitors. Tripteroside acetate inhibited platelet aggregation and ATP release induced by ADP, arachidonic acid, platelet-activating factor (PAF), collagen, ionophore A23187 and thrombin. The IC50 values of tripteroside acetate toward arachidonic acid- (100 microM) and collagen- (10 micrograms/ml) induced platelet aggregation were 10 and 30 micrograms/ml respectively. It inhibited thromboxane B2 formation of washed platelets caused by arachidonic acid, collagen, thrombin and ionophore A23187 and also that caused by the incubation of lysed platelet homogenate with arachidonic acid. Tripteroside acetate decreased the formation of inositolphosphate caused by thrombin, collagen and PAF, whereas it had no direct effect on fibrinogen-platelet interaction. It is concluded that xanthone derivatives inhibited platelet aggregation and release reaction by diminishing thromboxane formation and phosphoinositide breakdown.

Adenosine Diphosphate↗
PubMed1985

Synthesis of p-nitrophenyl beta-glycosides of (1----6)-beta-D-galactopyranosyl-oligosaccharides.

Sequential tritylation, benzoylation, and detritylation of p-nitrophenyl beta-D-galactopyranoside gave p-nitrophenyl 2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (2). Reaction of 2 with 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl bromide gave p-nitrophenyl O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----6) -2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (4) in 94% yield. Deprotection with sodium methoxide then gave the crystalline p-nitrophenyl O-(beta-D-galactopyranosyl)-(1----6)-beta-D-galactopyranoside (5). Condensation of 2 with 2,3,4-tri-O-benzoyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide (3) readily yielded the protected disaccharide p-nitrophenyl O-(2,3,4-tri-O-benzoyl-6-O-bromoacetyl-beta-D-galactopyranosyl)-(1----6) -2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (6) from which the bromoacetyl groups could be selectively removed. Condensation of the resulting material with tetra-O-benzoyl-alpha-D-galactopyranosyl bromide then yielded p-nitrophenyl O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----6)-O-(2,3,4 -tri-O-benzoyl-beta-D-galactopyranosyl)-(1----6)-2,3,4-tri-O-benzoyl-bet a-D -galactopyranoside, (8), which was converted into the crystalline trisaccharide p-nitrophenyl O-(beta-D-galactopyranosyl)-(1----6)-O-beta-D-galactopyranosyl)-(1----6) -beta -D-galactopyranoside (9) by treatment with sodium methoxide. Preliminary experiments on the interaction of p-(bromoacetamido)phenyl and p-isothiocyanatophenyl glycoside derivatives of some of these galacto-saccharides with monoclonal anti-(1----6)-beta-D-galactopyranan antibodies have been conducted.

Antibodies, Monoclonal↗
PubMed1985

Synthesis of methyl glycosides of beta-(1----6)-linked D-galactobiose, galactotriose, and galactotetraose having a 3-deoxy-3-fluoro-beta-D-galactopyranoside end-residue.

Methyl 2,4-di-O-acetyl-3-deoxy-3-fluoro-beta-D-galactopyranoside was synthesized by sequential tritylation, acetylation, and detritylation of methyl 3-deoxy-3-fluoro-beta-D-galactopyranoside, and used as the initial nucleophile in the synthesis of methyl beta-glycosides of (1----6)-beta-D-galacto-biose, -triose (20), and -tetraose (22) having a 3-deoxy-3-fluoro-beta-D-galactopyranoside end-residue. The extension of the oligosaccharide chains, to form the internal units in 20 and 22, was achieved by use of 2,3,4-tri-O-acetyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide as a glycosyl donor, and mercuric cyanide or silver triflate as the promotor. While fewer by-products were formed in the reactions involving mercuric cyanide, the reactions catalyzed by silver triflate were stereospecific and yielded only the desired beta (trans) products.

Carbohydrate Conformation↗
PubMed1989

Separation by liquid chromatography (under elevated pressure) of benzyl and nitrophenyl glycosides of oligosaccharides.

Liquid chromatography under elevated pressure (l.c.) was employed for the separation of some benzyl and nitrophenyl glycosides of a variety of mono-, di-, tri-, and tetra-saccharides. The separation was conducted on a Waters Carbohydrate Analysis column by use of a mixture of acetonitrile-water as the mobile phase. In general, monosaccharides emerged first from the column, followed sequentially by di-, tri-, and tetra-saccharides. It was observed that the pattern of substitution imparts a noticeable effect on the elution profiles of isomeric oligosaccharides. Also, substitution of a hydroxyl group with a methyl group, or its replacement with a fluorine atom, led to a substantial decrease in retention times of some oligosaccharides. Moreover, resolution was clearly enhanced, and retention times were congruently increased by decreasing the water content of the mobile phase.

Benzyl Compounds↗
PubMed1989

Synthesis of a common polysaccharide antigen of Pseudomonas aeruginosa as the 6-aminohexyl glycoside.

The synthesis is described of a tritylated 1,2-O-cyanoethylidene derivative (3) of the trisaccharide alpha-D-Rha-(1----2)-alpha-D-Rha-(1----3)-D-Rha. Triphenylmethylium perchlorate-catalysed polycondensation of 3 in the presence of 6-phthalimidohexyl 2,4-di-O-benzoyl-3-O-trityl-alpha-D-rhamnopyranoside followed by deprotection afforded the 6-aminohexyl glycoside of a D-rhamnan corresponding to a common polysaccharide antigen of Pseudomonas aeruginosa.

Glycosides↗
PubMed1990

Synthesis of disaccharide methyl glycosides related to the polysaccharide from Klebsiella serotype 40 and a study of their inhibition in the precipitin reaction.

The methyl glycosides of alpha-D-Manp-(1----4)-alpha-L-Rhap (3), alpha-L-Rhap-(1----3)-beta-D-Galp (4), beta-L-Rhap-(1----3)-beta-D-Galp (5), beta-D-Galp-(1----2)-alpha-L-Rhap (6), and beta-D-GlcpA-(1----2)-alpha-L-Rhap (7) have been synthesised and their inhibition reactions in the Klebsiella serotype 40 immune system have been studied. The results obtained accord with only one of two structures proposed for the repeating unit of the K40 antigen.

Carbohydrate Sequence↗
PubMed1990

O-alkylation at the anomeric centre for the stereoselective synthesis of Kdo-alpha-glycosides.

O-Alkylation at the anomeric centre of the dianion of 4,5:7,8-di-O-cyclohexylidene-3-deoxy-N-methyl-alpha-D-manno- octulopyranosonamide (1) with several triflates led diastereoselectively to the alpha-glycosides. In this way, lipopolysaccharide building-blocks containing alpha-Kdo-(2----6)-GlcN and alpha-Kdo-(2----6)-beta-GlcN-(1----6)-GlcN moieties were obtained and deployed in the synthesis of decyl 4,5,7,8-tetra-O-acetyl-3-deoxy-N-methyl-alpha-D-manno-2-octulopyranos idonamide (18), 2,3-di-O-tetradecanoyl-D-glycer-1-yl 4,5,7,8-tetra-O-acetyl-3-deoxy-N-methyl- alpha-D-manno-2-octulopyranosid-onamide (22), methyl 2,3,4-tri-O-acetyl-6-O-(methyl 4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D- manno-2-octulopyranosylonate)-alpha-D-glucopyranoside (28), 1-O-acetyl-2-deoxy-6-O-(methyl 4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2- octulopyranosylonate)-2-tetradecanoylamino-alpha-D-glucopyra nose (33), tert-butyldimethylsilyl O-(methyl 4,5:7,8-di-O-cyclohexylidene-3-deoxy-alpha-D- manno-2-octulopyranosylonate)-(2----6)-O-(3,4-di-O-benzyl-2-deoxy- 2- tetradecanoylamino-beta-D-glucopyranosyl)-(1----6)-3,4-di-O-benzyl -2-deoxy-2- tetradecanoylamino-alpha-D-glucopyranoside (36).

Alkylation↗
PubMed1990

Synthesis of a series of methyl beta-glycosides of (1----6)-beta-D-galacto-oligosaccharides having one residue deoxygenated at position 3.

Methyl beta-glycosides of beta-(1----6)-linked D-galactobioses (13 and 16) and -galactotrioses (21, 24, and 26) containing a 3-deoxy-beta-D-xylo-hexopyranosyl moiety either as one of the end units or the internal unit have been synthesized. The extension of the oligosaccharide chain was achieved, inter alia, by the use of two newly synthesized glycosyl donors derived from 3-deoxy-D-xylo-hexopyranose, namely, 2,4,6-tri-O-benzoyl-3-deoxy-a-D-xylo-hexopyranosyl chloride (8) and 2,4-di-O-benzoyl-6-O-bromoacetyl-3-deoxy-a-D-xylo-hexopyranosyl chloride (10). Glycosylation reactions were mediated by silver triflate under base-deficient conditions.

Carbohydrate Conformation↗
PubMed1991

Structure of pescaproside E, a fatty acid glycoside from Ipomoea pescaprae.

Three fatty acid glycosides, designated pescaprosides A, B, and E, have been isolated from Ipomoea pescaprae (family Convolvulaceae). Chemical studies on pescaproside E, the major product, led to its characterisation as a pentaglycoside of 11-hydroxyhexadecanoic acid. Its sugar chain was esterified with 2-methylbutanoic and lauric acids. The structure of the pentaglycoside has been established as O-alpha-L-rhamnopyranosyl-(1----3)-O-[alpha-L-rhamnopyranosyl- (1----4)]-O-alpha-L-rhamnopyranosyl-(1----4)-O-beta-D-fucopyranosyl-(1-- --2)- O-alpha-L-rhamnopyranosyl-(1----11)-oxyhexadecanoic acid.

Carbohydrate Conformation↗
PubMed1994

Facile synthesis of the sugar cores from phenylpropanoid glycosides.

Allyl 2-O-benzoyl-4,6-O-benzylidene-alpha-D-glucopyranoside (3), obtained by selective benzoylation of allyl 4,6-O-benzylidene-alpha-D-glucopyranoside (2) with benzoyl chloride-imidazole in anhydrous chloroform, reacted with 2, 3, 4-tri-O-benzoyl-alpha-L-rhamnopyranosyl bromide to give a disaccharide derivative (4), and an important intermediate (5) was obtained by cleavage of its acetal. Treatment of 5 with a series of glycopyranosyl bromides, protected by acetyl or benzoyl groups in benzene-nitromethane in the presence of Hg(CN)2 as a catalyst afforded four trisaccharides (6-9). The disaccharide (5) and trisaccharides (6-9) constitute the sugar cores of phenylpropanoid glycosides. A new glycosyl anomeric leaving group, trichloroacetoxy, was employed to prepare the disaccharide (4) and trisaccharides residue (8) efficiently and with high stereoselectivity.

Carbohydrate Conformation↗
PubMed1995

Preparation of alpha -and beta-dienyl glycosides used as dienes in aqueous Diels-Alder reactions. Influence of the carbohydrate moiety on the thermodynamics of the reaction.

A series of 1,3-butadienyl glycosides (mono- and di-saccharides) have been prepared and the kinetics of their Diels-Alder reaction with buten-2-one in water have been studied. The activation parameters for these aqueous cycloadditions provide clues for the hydration structure of such glyco-organic compounds.

Carbohydrate Sequence↗
PubMed1995

Reductive cleavage of glycosides with borane complexes in the presence of boron trifluoride etherate.

Mixtures consisting of five equivalents each of borane.methyl sulfide and boron trifluoride etherate per equivalent of acetal or five equivalents of various amine-borane complexes and 10 equivalents of boron trifluoride etherate readily accomplished reductive cleavage of the glycosidic linkages of several per-O-methylated monosaccharides and polysaccharides. In all cases, the expected products were obtained in the expected molar proportions and no artifactual products were observed. Reductive-cleavage analysis using these reagents is particularly convenient because the reagents themselves are easy to handle and because subsequent acetylation of the products is accomplished in situ.

Acetylation↗
PubMed1993

Inhibition of the autoxidation of linoleic acid by phenylpropanoid glycosides from Pedicularis in micelles.

The activities of six phenylpropanoid glycosides as chain-breaking antioxidants have been studied for the autoxidation of linoleic acid in cetyl trimethylammonium bromide (CTAB) micelles at 37 degrees C. Verbascoside, isoverbascoside, echinacoside and pedicularioside A, which possess four phenolic hydroxyl groups, exhibited antioxidant activities, while cistanoside D possessing only two phenolic hydroxyl groups and permethyl verbascoside without phenolic hydroxyl group did not suppress the oxidation appreciably. The ratio of rate constants for inhibition and propagation kinh/kp and stoichiometric factor n were determined.

Amidines↗
PubMed1993

Methyl alpha-glycoside of N-thioacetyl-D-neuraminic acid: a potential inhibitor of influenza A virus. A 1H NMR study.

The binding of influenza A virus hemagglutinin to its cell surface receptor, alpha-linked 5-N-acetylneuraminic acid (sialic acid), was studied in solution. The effect of structural modifications introduced into the N-acetyl group of the sialic acid on the binding was monitored by determining the dissociation constants by proton nuclear magnetic resonance (1H NMR) spectroscopy. Methyl alpha-glycoside of N-thioacetylneuraminic acid showed high, whereas the corresponding N-methylcarbamoylneuraminic acid exhibited relatively low binding affinity towards the hemagglutinin.

Electrophoresis, Polyacrylamide Gel↗
PubMed1994

Stereochemistry of the hydrolysis of glycosidic linkage by endo-beta-1,4-xylanases of Trichoderma reesei.

Methyl beta-D-xylotrioside was used as a non-reducing substrate to investigate the stereochemistry of hydrolysis of beta-1,4-xylopyranosidic linkage by purified endo-beta-1,4-xylanases (EC 3.2.1.8) of Trichoderma reesei, employing 1H NMR spectroscopy. The fungus produces one acidic species (pI 4.8-5.5), designated as EXI, and one alkaline species (pI 8.5-9.0), designated as EXII. Both enzymes were found to cleave the xylotrioside predominantly to methyl beta-D-xyloside and xylobiose. Monitoring of the intensity of the H-1 signals of alpha- and beta-xylobiose during the time course of hydrolysis clearly showed that both enzymes liberate the beta-anomer of xylobiose, i.e. a product with anomeric configuration identical with that of the cleaved glycosidic linkage. This means that both EXI and EXII belong to the so-called retaining glycanases that utilize the double displacement reaction mechanism of hydrolysis.

Endo-1,4-beta Xylanases↗
PubMed1979

Chromatographic analysis of hydroxylysine glycosides and acid hydrolyzates.

A single-column chromatographic technique for the analysis of hydroxylysine glycosides and acid hydrolyzates is described. This technique employs a Durrum D-500 amino acid analyzer equipped with a standard 48 cm X 1.8 mm column packed with DC-4A resin. Resolution was achieved with four sodium citrate buffers and four column temperatures. Products of glycoprotein hydrolysis including cysteic acid, methionine sulfoxide, 4-hydroxyproline, alpha-aminobutyric acid, glucosamine, galactosamine, hydroxylysine, tryptophan and the internal standard, norleucine, are resolved. The completely automated procedure takes 185 min per run and can measure amino acid residues in the nanomole range.

Animals↗