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At least 1,477 records · Page 82Linked to original sources
PubMed2007

Herbal modulation of drug bioavailability: enhancement of rifampicin levels in plasma by herbal products and a flavonoid glycoside derived from Cuminum cyminum.

The bioavailability of rifampicin (RIF) in a fixed dose combination (FDC) used for the treatment of tuberculosis remains an area of clinical concern and several pharmaceutical alternatives are being explored to overcome this problem. The present study presents a pharmacological approach in which the bioavailability of a drug may be modulated by utilizing the herb-drug synergism. The pharmacokinetic interaction of some herbal products and a pure molecule isolated from Cuminum cyminum with RIF is shown in this paper. An aqueous extract derived from cumin seeds produced a significant enhancement of RIF levels in rat plasma. This activity was found to be due to a flavonoid glycoside, 3',5-dihydroxyflavone 7-O-beta-D-galacturonide 4'-O-beta-D-glucopyranoside (CC-I). CC-I enhanced the Cmax by 35% and AUC by 53% of RIF. The altered bioavailability profile of RIF could be attributed to a permeation enhancing effect of this glycoside.

Animals↗
PubMed2001

Gas chromatography/mass spectrometry demonstration of steryl glycosides in eucalypt wood, Kraft pulp and process liquids.

The occurrence of steryl glycosides (SG) and acyl steryl glycosides (ASG) in eucalypt (Eucalyptus globulus) wood has been investigated. These compounds were analyzed as their trimethylsilyl ethers by gas chromatography/mass spectrometry (GC/MS) using a 15 m length high-temperature capillary column with a thin film, and identified on basis of their mass spectra and relative retention times comparing with those of authentic standards. Significant amounts of SG were identified in eucalypt wood whilst only traces of ASG could be detected. Eucalypt SG and ASG occur in the pyranoside form, which is readily distinguishable from the furanoside configuration by the mass spectra of their trimethylsilyl derivatives. The sterol part of the SG and ASG consisted of sitosterol, being sitosteryl 3beta-D-glucopyranoside and sitosteryl (6'-O-palmitoyl)-3beta-D-glucopyranoside, the major SG and ASG found in E. globulus wood. The presence of SG and ASG was also investigated after kraft cooking by analyzing unbleached pulp and process water samples. The GC/MS results also revealed the presence of sitosteryl 3beta-D-glucopyranoside in these samples. By contrast, no ASG could be detected. Therefore, we have shown that SG survive the kraft cooking and can be found at least partly intact after pulping, being a possible cause for pitch deposits together with free and esterified sterols.

Acylation↗
PubMed1993

Solution conformation of the tetrasaccharide glycoside Xyl beta 1-(Man alpha 1-3)2Man beta 1-4Glc beta 1R from the mollu-series glycosphingolipids.

The conformation of Xyl beta 1-(Man alpha 1-3)2Man beta 1-4Glc beta 1-OCH2CH(N3)CH(OH) CH = CHC13H27 tetrasaccharide glycoside in Me2SO-d6 was investigated with use of a distance mapping procedure based on rotating-frame NOE and hydrogen bond constraints, and Molecular Mechanics calculations. The Man alpha 1-3Man beta linkage was found to be well defined in a single conformation, whereas some flexibility could be assumed for the remaining two glycosidic linkages. Similar conclusions, though based on a smaller number of constraints, were drawn for the title compound anchored in mixed D2O/dodecylphosphocholine-d38 micelles.

Carbohydrate Conformation↗
PubMed1996

Enzymatic synthesis of the N-glycosidic bond by beta-aspartylation of glycosylamines.

Glycosylasparaginase (EC 3.5.1.26) is an amidase, which cleaves the N-glycosidic linkage during glycoprotein degradation leading to the liberation of L-aspartic acid from various glycoasparagines. In this work we demonstrate that glycosylasparaginase is also capable of catalyzing the synthesis of the N-glycosidic bond by N-beta-aspartylation of beta-glycosylamine using 1-amino-N-acetylglucosamine as the nucleophile and L-aspartic acid beta-methyl ester as the beta-aspartyl donor. Kinetic studies indicated that beta-glycosylamine has 1390-fold higher reactivity than water in the de-beta-aspartylation of the beta-aspartylenzyme, indicative of the presence of a beta-glycosylamine binding sub-site at the substrate binding site of glycosylasparaginase. The reaction can be applied to glycosylaparaginase-catalyzed biosynthesis of novel glycoasparagines.

Aspartic Acid↗
PubMed1997

Dual effect of digitalis glycosides on norepinephrine release from human atrial tissue and bovine adrenal chromaffin cells: differential dependence on [Na+]i and [Ca2+]i.

It was the aim of the present study (1) to characterize the influence of Na+/K(+)-ATPase inhibition by the digitalis glycoside ouabain on both spontaneous and nicotine-evoked norepinephrine release from the human heart; and (2) to further investigate the role of glycoside-induced changes in [Na+]i and [Ca2+]i (determined by microfluorimetry) for catecholamine release. The latter experiments were performed in bovine adrenal medullary chromaffin cells (BCC), an established cell culture model for sympathetic nerves. Ouabain (1-1000 mumol/l) exerted a dual effect on norepinephrine release (determined by HPLC) from incubated human atrial tissue: (I) Ouabain induced a concentration-dependent increase in norepinephrine release, that was calcium-independent and almost completely prevented by blockade of the uptake1-carrier by desipramine (1 mumol/l). The characteristics of this release process are consistent with a non-exocytotic mechanism. (II) In addition, ouabain augmented the nicotine-evoked (1-100 mumol/l) calcium-dependent norepinephrine release, which can be considered to be exocytotic. Na+/K(+)-ATPase inhibition also reduced the threshold concentration of nicotine from 10 to 1 mumol/l and it delayed the rapid tachyphylaxis of its norepinephrine releasing effect in human atrial tissue. In BCC, ouabain increased [Na+]i, [Ca2+]i and [3H]-norepinephrine release in parallel. Under calcium-free conditions, not only the ouabain-induced increase in [Na+]i, but also [3H]-norepinephrine release were enhanced. The ouabain-induced [3H]-norepinephrine release was always closely related to changes in [Na+]i, indicating a key role of [Na+]i for this calcium-independent non-exocytotic norepinephrine release. In addition, pretreatment with ouabain (1 mmol/l) augmented the nicotine-evoked (0.1-10 mumol/l) increments in [Na+]i, [Ca2+]i and [3H]-norepinephrine release. As nicotine-induced norepinephrine release depends on an increase in both [Na+]i and [Ca2+]i, these findings are indicative of an ouabain-mediated facilitation of exocytosis. In conclusion, increasing [Na+]i and [Ca2+]i inhibition of Na+/K(+)-ATPase by ouabain triggers non-exocytotic norepinephrine release, and facilitates nicotine-evoked exocytotic norepinephrine release.

Adrenal Medulla↗
PubMed1984

Two receptors for cardiac glycosides in the heart.

Specific binding of 3H-ouabain to rat cardiac cell membranes revealed a high affinity and a low affinity site. In order to test the pharmacological significance of these different types of binding sites, specific 3H-ouabain binding, force of contraction and 86Rb+-uptake were measured simultaneously in contracting cat papillary muscles and in guinea pig atria. The results in the digitalis sensitive cat shows one type of cardiac glycoside receptors with high affinity (KD approximately 10(-7) M) for ouabain. The occupation of this receptor runs parallel with an increase in force of contraction and an inhibition of 86Rb+-uptake. In the rather digitalis insensitive guinea pig, 3H-ouabain binding also runs parallel with increased force of contraction, 86Rb+-uptake, however, is only inhibited at toxic glycoside concentrations. Thus, in rat and guinea pig heart there exist at least two different digitalis receptors--the high affinity receptor seems to be coupled to inotropic effects, the low affinity receptor is linked to inhibition of (Na+ + K+)-ATPase.

Animals↗
PubMed1995

Influence of the glycosidic torsion angle on 13C and 15N shifts in guanosine nucleotides: investigations of G-tetrad models with alternating syn and anti bases.

The effect of the glycosidic torsion angle on 13C and 15N shifts of the sugar and base moieties of guanosine nucleotides was investigated by comparing the sites in two model G-tetrad oligodeoxynucleotides that contain guanosine residues alternately with syn and anti bases. The sugar puckering has been shown to be C2'-endo for both cases. It was observed that, for the instances with syn bases, the C1' through C4' carbons showed shifts that may be distinguished from those normally found in B-DNA-like structures. C1', C3' and C4' moved to lower field, while C2' moved to higher field. Effects of the change in glycosidic torsion angle were also seen in the shifts of base carbons and nitrogens in the five-membered ring portion of the base. Characterization of the shift variation associated with this conformational change may be useful in developing the use of 13C shifts as a tool in conformational analysis of oligonucleotides.

Base Sequence↗
PubMed1982

Protein binding of anthraquinone glycosides, with special reference to adriamycin.

The binding of anthraquinone glycosides (adriamycin, adriamycinol, daunorubicin, daunorubicinol, and 4'epiadriamycin) to human serum albumin and human plasma has been studied by equilibrium dialysis. About 62% of adriamycin was bound to human serum albumin (45 g/l). Only minor variations in the degree of binding were observed between the anthraquinone glycosides. The binding degree of adriamycin in plasma from cancer patients was not significantly different from that observed in healthy volunteers, the fraction of free adriamycin being 24.56% +/- 4.51%, and 27.67% +/- 2.78%, respectively. The plasma albumin concentration was significantly lower in cancer patients than in the healthy volunteers (26.90% +/- 5.88% and 39.24% +/- 1.74%, respectively). In cancer patients the fraction of free adriamycin decreased with increasing plasma albumin concentration.

Adsorption↗
PubMed1977

The formation of glycosidic bonds in yeast glycoproteins. Intracellular localisation of the reactions.

Membranes of Saccharomyces cerevisiae were separated on urografin gradients. The specific activity of the light membranes (endoplasmic reticulum), the Golgi-like vesicles and the plasma membrane in transferring mannosyl residues from GDP-mannose to mannoproteins and to dolichyl monophosphate has been determined. The first mannose of the O-glycosidically linked manno-oligosaccharides is incorporated with the highest specific activity by the endoplasmic reticulum. The incorporation of the second to fourth mannosyl groups is catalysed with increasing activity also by the Golgi-like vesicles and the plasma membrane. The incorporation of mannosyl groups into weak alkali-stable positions (N-glycosidically linked chains) is carried out with almost the same specific activity by all three membrane fractions, however, dolichol-dependent and -independent steps could not be distinguished as yet. The results are discussed in terms of a sequential addition of sugar residues along the route of export of the mannoprotiens. The dolichol-dependent steps seem to occur on the endoplasmic reticulum and thus very early in the event.

Cell Membrane↗
PubMed1986

Absorption, metabolism and elimination of strophanthus glycosides in man.

In 33 healthy male volunteers, given a single oral and intravenous dose of cymarin (k-strophanthin-alpha), k-strophanthoside (k-strophanthin-gamma) and ouabain (g-strophanthin), enteral absorption and renal excretion of these glycosides and their metabolites were investigated by radioimmunoassay and HPLC. Cymarin was absorbed at 47% of the given dose. After intravenous injection 46% and after oral administration 21% of the given dose, i.e. the total amount as detected by radioimmunoassay which consisted of the unchanged glycoside and its metabolites, were excreted by the kidneys mainly as conjugated metabolites. The half-life of elimination, calculated from the total excreted amount was 13 h (i.v.) and 23 h (p.o.), respectively. k-Strophanthoside was absorbed at 16% of the given dose. After i.v.-injection 73% of the given dose was excreted by the kidneys with a half-life of elimination of 99 h. From this total amount about 70% was excreted as the unchanged drug, the remaining 30% as various metabolites. After oral administration 11% of the given dose were excreted with a half-life of elimination of 22 h. 80% of this amount consisted mainly of conjugated k-strophanthoside and conjugated metabolites as k-strophanthin-beta, cymarin, k-strophanthidin, cymarol and k-strophanthidol. Only 6% was excreted as the unchanged drug. Ouabain was absorbed after oral administration to a minimum of 1.4%. Given intravenously a total renal excretion of 33% of the given dose with a half-life of elimination of 23 h was measured. Of this 80% was unchanged ouabain.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1980

Effect of 1,25-dihydroxycholecalciferol and 1,25-dihydroxycholecalciferol glycoside on 2,3-diphosphoglycerate levels of the rat erythrocyte.

The erythrocytes of rats treated with 1, 25-dihydroxycholecalciferol or 1, 25-dihydroxycholecalciferol glycoside showed decreased levels of 2, 3-diphosphoglycerate. The same result has been obtained in vitro, indicating a direct effect of the sterol on the red cell. The glycoside is less active than the free sterol in vivo and more active in vitro. The decreased levels of diphosphoglycerate induced tissue hypoxia as shown by a higher plasma lactate/pyruvate ratio and a three fold increase in plasma erythropoietin concentration.

Animals↗
PubMed1977

Serum glycoside concentrations after single or repeated intravenous doses of beta-methyl-digoxin and digoxin.

The aim of the present investigation was to estimate the ratio of the intravenous doses of beta-methyl-digoxin and digoxin required to produce identical serum glycoside concentrations in man. 20 patients on intravenous maintenance therapy were changed from beta-methyl-digoxin to the identical dose of digoxin or vice versa. Each drug was given for 7 days. Serum concentrations 13% higher were found during administraton of beta-methyl-digoxin. Assuming a half life of 60 h after withdrawal, the dose of digoxin producing the same minimum serum concentration was estimated to be 1.16 times higher than that of beta-methyl-digoxin. 18 healthy volunteers received 0.4 mg beta-methyl- digoxin, and 23 the same dose of digoxin, as an intravenous infusion over 2 h. The serum concentrations and urinary glycoside excretion were measured over a period of 32 hrs. During the first hour after the infusion the serum concentration of digoxin declined more rapidly than that of beeta-methyl-digoxin. Thereafter, the ratio of the serum concentrtions did not change appreciably up to the end of the investigation. The area under the serum concentration/time curve was about 13% greater for beta-methyl-digoxin than for digoxin; this difference was not significant. The average renal clearance was 96 +- 9 ml for beta-methyl-digoxin, 151 +- 13 ml for digoxin. Since the total body clearance of digoxin is only about 1.16 times higher than that of beta-methyl-digoxin, the lower renal clearance of beta-methyl-digoxin must partly be compensated by higher extrarenal clearance. From the ratios of the areas under the serum concentration/time curves after single doses of beta-methyl-digoxin and digoxin, and the minimum serum concentrations during maintenance therapy, it was concluded that the dose of digoxin to produce the same average serum concentrations would be about 1.15 times higher than that of beta-methyl-dogoxin. In comparison wtih the large variations in individual dosage of digoxin and beta-methyl-digoxin, this difference is too small to be of practical importance.

Aged↗
PubMed2004

Astonishing diversity of natural surfactants: 1. Glycosides of fatty acids and alcohols.

Alkyl and fatty acid glycosides have become of great commercial interest in general and specifically for the pharmaceutical, cosmetic, and food industries. Natural surfactants are good sources for future chemical preparation of these glycosides. This review article shows an astonishing diversity of natural surfactants that could be used in laboratories and industry. More than 250 natural surfactants, including their chemical structures and biological activities, are described in this review article.

Biological Factors↗
PubMed1990

Colorimetric determination of N-acetylhexosamine-terminating O-glycosidically linked saccharides in mucins and glycoproteins.

A sensitive colorimetric assay for detecting mucins and glycoproteins rich in O-glycosidically linked saccharides is reported. The method combines the susceptibility of N-acetylgalactosamine terminating O-glycosidically linked saccharides to beta-elimination with the Morgan-Elson reaction for N-acetylhexosamines with free reducing ends. All mucin and mucin-type glycoproteins but none of the serum-type glycoproteins tested resulted in characteristic color production. All mucins tested gave linear responses in the range 5 to 200 micrograms and the assay was also adapted to the microscale involving the use of 96-well microtiter plates. The microassay in which the volumes of samples and reagents are scaled down 2.5-fold was particularly useful in monitoring of mucins, in the presence of other glycoconjugates, in large numbers of samples obtained during fractionation procedures. Cesium chloride, cesium bromide, potassium thiocyanate, and various detergents do not interfere with the colorimetric determination. Guanidine hydrochloride, cesium trifluoroacetate, and beta-mercaptoethanol decreased color by 30 to 45%; however, the interference was not serious to prevent the use of the method for detection of mucins in their presence. The use of the method for the specific detection of mucin during fractionation by gel filtration and density gradient centrifugation of cystic fibrosis sputum samples is demonstrated.

Acetylgalactosamine↗
PubMed1987

Cardiac glycosides stimulate phospholipase C activity in rat pinealocytes.

Ouabain and related cardiac glycosides stimulate phospholipase C activity 5-fold in rat pinealocytes. The combined treatment of ouabain and norepinephrine, which also stimulates phospholipase C, produces an additive effect. The effects of either ouabain or norepinephrine are blocked by EGTA. However, there are notable differences. The stimulatory effect of ouabain is lost when extracellular Na+ is reduced to 20 mM and is not blocked by prazosin. In contrast, the stimulatory effect of norepinephrine is not blocked when extracellular Na+ is reduced to 20 mM but is blocked by prazosin. Ouabain appears to increase phospholipase C activity through a mechanism involving inhibition of Na+,K+-ATPase, and an accumulation of intracellular Na+ and Ca2+, not involving alpha 1-adrenoceptors. These findings raise the possibility that activation of phospholipase C might be a more general effect of cardiac glycosides.

Animals↗
PubMed1983

Oligosaccharides from "standardized intermediates". Synthesis of a branched tetrasaccharide glycoside isomeric with the blood-group B, type 2 determinant.

Building block derivatives of the component monosaccharides were used to construct the tetrasaccharide glycoside 15, in which an alpha-D-Galp-(1 leads to 4)-D-Gal linkage replaces the alpha-(1 leads to 3) linkage of the human blood-group B, type 2, determinant structure. The initial coupling of 2-O-benzoyl-3,6-di-O-benzyl-4-O-(tetrahydropyran-2-yl)-alpha-D-galactopyranosyl chloride to allyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranoside was followed by selective deprotection of the disaccharide product, either at O-4' (to give 8) or O-2' (to give 3). The conversion of 8 into 15 involved successive coupling with tetra-O-benzyl-alpha-D-galactopyranosyl bromide (8 leads to 11), O-debenzoylation at O-2' (11 leads to 12), coupling with tri-O-benzyl-alpha-L-fucopyranosyl bromide (12 leads to 14), and O-debenzylation by hydrogenolysis (14 leads to 15). Alternatively, 3 was alpha-L-fucosylated to give 6, and 6 was selectively deprotected at O-4' to give 7. However, attempts to alpha-D-galactosylate 7 were unsuccessful. The unsubstituted forms of the intermediate disaccharide (8) and trisaccharide (12) glycosides were obtained by appropriate deblocking procedures.

ABO Blood-Group System↗
PubMed1984

Synthesis of spacer-arm, lipid, and ethyl glycosides of the trisaccharide portion [alpha-D-Gal-(1----4)-beta-D-Gal-(1----4)-beta-D-Glc] of the blood-group Pk antigen: preparation of neoglycoproteins.

The title compounds were prepared via the acetylated 2-bromoethyl glycoside 11 of alpha-D-Gal-(1----4)-beta-D-Gal-(1----4)-beta-D-Glc by displacement of bromide ion with methyl 3- mercaptopropionate , octadecanethiol , and hydrogen, respectively. Silver triflate -promoted glycosylation of 2-bromoethyl 2,3,6-tri-O-benzyl-beta-D-glucopyranoside with 2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl) -alpha -D-galactopyranosyl bromide gave 11. A tetradeuterated analogue of 11 was prepared by essentially the same route. The spacer-arm glycoside formed from methyl 3- mercaptopropionate was coupled to bovine serum albumin and keyhole limpet haemocyanin.

Blood Group Antigens↗
PubMed1984

Synthesis of spacer-arm, lipid, and ethyl glycosides of the terminal trisaccharide [alpha-D-Gal-(1----4)-beta-D-Gal-(1----4)-beta-D-GlcNAc] portion of the blood-group P1 antigen: preparation of neoglycoproteins.

The title compounds were prepared via the acetylated 2-bromoethyl beta-glycoside (5) of alpha-D-Gal-(1----4)-beta-D-Gal-(1----4)-beta-D-GlcNAc by displacement of bromide ion with methyl 3-mercaptopropionate, octadecanethiol, and hydrogen, respectively. Silver triflate-promoted glycosylation of 2-bromoethyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranoside with 2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl) -alpha-D-galactopyranosyl bromide gave 5. The spacer-arm glycoside derived from methyl 3-mercaptopropionate was coupled to bovine serum albumin and key-hole limpet haemocyanin to give neoglycoproteins.

Blood Group Antigens↗