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PubMed1985

Cellular mechanism of action of cardiac glycosides.

It has long been known that cardiac glycosides can inhibit the membrane sodium-potassium (Na+-K+) pump, raising intracellular Na+. However, at clinical concentrations of cardiac glycosides, a change in intracellular Na+ that correlates with a change in cardiac contraction has been very difficult to demonstrate. The recent use of Na+-sensitive microelectrodes in the experimental laboratory has made intracellular Na+ measurements possible. A doubling of contraction strength in vitro is associated with a change of only approximately 1 mM intracellular Na+. Another membrane transport system, the Na+-Ca2+ exchange system, exchanges extracellular Na+ for intracellular Ca2+. If this system is responsible for regulating intracellular Ca2+, then it would be very sensitive to the transmembrane Na+ concentration gradient. This influence of intracellular Na+ on Na+-Ca2+ exchange is though to be the cellular basis of the positive inotropic action of digitalis. However, a number of issues remain unresolved, such as the extent of Na+-K+ pump inhibition by the level of cardiac glycoside achieved clinically.

Action Potentials↗
PubMed1973

The time courses of the changes in contractile force and in transmembfane potentials induced by cardiac glycosides in guinea-pig papillary muscle.

1. The effects of ouabain, digoxin, digoxigenin monodigitoxoside, digoxigenin bisdigitoxoside and digitoxigenin bisdigitoxoside on the force of contraction and on the transmembrane action potential were compared in isolated papillary muscles of guinea-pigs.2. All cardiac glycosides studied had a dose-dependent positive inotropic effect and simultaneously shortened the duration of the action potential at all levels of repolarization from the start of drug action.3. In every instance, the reduction of the action potential duration developed more slowly than the increment in contractile force. However, the ratios between the two rates were independent of the concentrations used and seemed to be characteristic for the individual cardiac glycosides.4. All cardiac glycosides had a biphasic effect on the time-to-peak tension. An initial increase was followed by a dose-dependent decrease.5. The results are discussed with respect to the possible sites of action. Taking into account the different rates as well as the different ratios, it is proposed that more than one site of action is involved in producing the different effects of cardiac glycosides on heart muscle.

Action Potentials↗
PubMed2000

Cardenolide and oxypregnane glycosides from the root of Asclepias incarnata L.

Twenty-nine new oxypregnane glycosides were obtained along with two known cardenolides, frugoside and gofruside, and three known 12-O-acylated pregnane glycosides from the roots of Asclepias incarnata L. (Asclepiadaceae). By detailed studies of the 1H- and 13C-NMR spectra, the structures were determined to be tri- to penta glycosides of isolineolon, 12-O-acetyllineolon, ikemagenin, 12-O-benzoylisolineolon, and two new 12-O-acylated pregnanes.

Cardenolides↗
PubMed1990

[Synergism in the action of gamma radiation and cardiac glycosides].

Synergism of gamma radiation with 137Cs and cardiac glycosides was investigated in experiments on mice and transplantable Raji tumor cells. A single ip administration of these drugs at nontoxic concentrations 30-60 min. after irradiation at the LD30/30 resulted in the survival of 13-20% of animals and the reduction of the mean survival time up to 8.4-12.5 days versus 22.3 days in the control group. Synergism was slightly decreased at administration of glycosides 24 h after irradiation. Glycosides introduced in the irradiated (at a dose of 1-2.5 Gy) human lymphoblastic line caused sharp suppression of lymphoma growth and cellular lysis in experiments in vitro. One hundred per cent death of cells was noted after the use of the drugs at mean toxic concentrations.

Animals↗
PubMed1984

[Effect of plant glycosides on resistance and capacitance vessels].

In the anaesthetized cat, SCOA ( Miroton ), a product which contains extracts from Scilla , Convallaria , Oleander and Adonis , displays not only its well-known positive inotropic effect but has also constrictor effects on veins when applied in intravenous doses of 21.5-100 GPU /kg ( GPU = guinea-pig units, i.e. cardiotoxic equivalents related to 1 g body weight of guinea-pigs). The latter effect differs in that it is somewhat more prolonged. With intraduodenal administration the doses required to achieve equal peak effects as with intravenous injection are about 4 times larger and this suggests a relatively good enteral availability in the cat. SCOA constricts not only veins but also arteries. However, this latter effect is comparatively small and occurs only after intraarterial infusion of high doses (9.1 and 91 GPU /min, respectively).--The cardiac glycosides contained in the drug product primarily account for its vasoactive qualities. The venous constrictor effect correlates with the guinea-pig units. In qualitative respects, the pure glycosides cymarin , convallatoxin , proscillaridin , and scillaren exert equal effects. There is, however, evidence that the correlation between the effect on veins and on the heart differs for the glycosides tested. Based on equal guinea-pig units, the adonis extract, for instance, acts on capacitance vessels about twice as much as scilla , oleander and convallaria extracts. Cymarin , too, has a stronger effect on veins than would be expected from its cardiotoxic effect. The action on arteries and veins are based on different mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Influence of stereoisomeric glucose, galactose and mannose residues on fragmentation at their glycosidic linkages in post-source decay fragment analyses for oligosaccharides using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The isomeric sugar branched beta-cyclodextrin (CD) derivatives (Glc-beta CD, Gal-beta CD, and Man-beta CD) were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. In the MALDI post-source decay (PSD) fragmentation of Glc-beta CD, Gal-beta CD and Man-beta CD, the fragment ions of [M-Glc]+, [M-Gal]+ and [M-Man]+ were produced by the one-site cleavage of the alpha 1-6 glycosidic linkage at the branch (Y-type fragmentation). The abundances of [M-Gal]+ ions were much higher than that of [M-Man]+. These results indicated that Glc-beta CD and Gal-beta CD were distinguishable from Man-beta CD and that Y-type fragmentations of the branched glycosidic linkage at the glycosyl donors of alpha-D-Glc and alpha-D-Gal were more predominant than that at the glycosyl donor of alpha-D-Man by MALDI-PSD fragment analysis. It was concluded that the abundances of PSD fragment ions depended on the stereochemistry of the glycosyl donors in the cleavage of the glycosidic linkage of the oligosaccharides in MALDI-TOF mass spectra.

Carbohydrate Sequence↗
PubMed2000

Investigation of stretching vibrations of glycosidic linkages in disaccharides and polysaccharides with use of IR spectra deconvolution.

The results are presented for the deconvolution of IR spectra of disaccharides and polysaccharides with alpha and beta configurations of the 1 --> 4 glycosidic linkage (maltose, cellobiose, amylose, and cellulose), as well as of their corresponding monosaccharides (alpha- and beta-D-glucose) in the 1200-920 cm(-1) frequency range. It is established that a characteristic of di- and polysaccharides with 1 --> 4 glycosidic linkage is the appearance of new absorption bands in the 1175-1140 cm(-1) spectral range, as opposed to the IR spectra of monosaccharides. This can be a spectroscopic manifestation of the glycosidic linkage formation. In the 1000-970 cm(-1) frequency range, absorption bands, which are not observed in the monomer spectrum, are separated as a result of the deconvolution of the IR spectra of cellobiose and cellulose. The number of bands in this range remains unchanged for maltose and amylose, as compared to the monomer spectra. It is shown that the application of the method of deconvolution leads to a considerable enhancement in the resolution of the absorption bands in the IR spectra of mono-, di-, and polysaccharides.

Disaccharides↗
PubMed2000

Differential expression of glycoside residues in the mammalian zona pellucida.

The mammalian zona pellucida is an extracellular matrix surrounding the oocyte, and is composed of three major glycoproteins, ZP1, ZP2, and ZP3. Previous studies have suggested that the sperm receptor activity of the zona pellucida resides in specific oligosaccharide chains on the ZP3 glycoprotein. However, the nature of the terminal monosaccharide(s) on these glycosidic chains to which sperm bind is a matter of active debate. Evidence has been presented to support a role for at least three distinct monosaccharides in sperm binding, alpha-galactose, L-fucose on Lewis X structures, and beta-N-acetylglucosamine. Previous studies have shown that beta-N-acetylglucosamine is uniformly distributed throughout the zona matrix. In this study, we have investigated the expression and distribution of alpha-galactose and fucose moieties during the maturation of the zona pellucida in mouse, rat, and hamster. Interestingly, alpha-galactose residues are expressed only during later stages of zona secretion and, consequently, are confined to the inner portions of the mature zona pellucida in mouse and rat. In hamster, alpha-galactose residues are only detectable in the zona pellucida of ovulated eggs, and are not found in ovarian oocytes. Fucosyl residues linked to Lewis X glycosides are not detectable at any stage of zona maturation in these three species, whereas fucose linked to N-linked core oligosaccharides are present throughout the zona. These studies indicate a previously unappreciated heterogeneity in the composition of zona glycosides. The specific localization of alpha-galactose residues to the inner portions of the zona matrix suggest a role in the later stages of sperm penetration through the zona. Finally, due to their absence from the zona surface, alpha-galactose and Lewis X fucosyl residues are not likely to be mediators of primary sperm binding.

Animals↗
PubMed2001

Mixed-linkage cellooligosaccharides: a new class of glycoside hydrolase inhibitors.

A new class of inhibitors for beta-D-glycoside hydrolases, in which a single alpha-(1-->4)-glycosidic bond is incorporated into an otherwise all-beta-(1-->4)-linked oligosaccharide, is described. Such mixed beta/alpha-linkage cellooligosaccharides are not transition-state mimics, but instead are capable of utilising binding energy from numerous subsites, spanning either side of the catalytic centre, without the need for substrate distortion. This binding is significant; a mixed alpha/beta-D-tetrasaccharide acts competitively on a number of cellulases, displaying inhibition constants in the range of 40-300 microM. Using the Bacillus agaradhaerens enzyme Cel5A as a model system, one such mixed beta/alpha-cellooligosaccharide, methyl 4(II),4(III)-dithio-alpha-cellobiosyl-(1-->4)-beta-cellobioside, displays a K(i) value of 100 microM, an inhibition at least 150 times better than is observed with an equivalent all-beta-linked compound. The three-dimensional structure of B. agaradhaerens Cel5A in complex with methyl 4(II),4(III)-dithio-alpha-cellobiosyl-(1-->4)-beta-cellobioside has been determined at 1.8 A resolution. This confirms the expected mode of binding in which the ligand, with all four pyranosides in the (4)C(1) chair conformation, occupies the -3, -2 and +1 subsites whilst evading the catalytic (-1) subsite. Such "by-pass" compounds offer great scope for the development of a new class of beta-D-glycoside hydrolase inhibitors.

Bacillus↗
PubMed2000

Total synthesis of everninomicin 13,384-1--Part 4: explorations of methodology; stereocontrolled synthesis of 1,1'-disaccharides, 1,2-seleno migrations in carbohydrates, and solution- and solid-phase synthesis of 2-deoxy glycosides and orthoesters.

Methods for the stereocontrolled construction of 1,1'-disaccharides, 2-deoxy glycosides, and orthoesters are reported. Specifically, a tin-acetal moiety was utilized to fix the anomeric stereochemistry of a carbohydrate acceptor leading to an efficient and stereoselective synthesis of 1,1'-disaccharides, while a newly discovered 1,2-phenylseleno migration reaction in carbohydrates opened entries to 2-deoxy glycosides and orthoesters. Thus, reaction of 2-hydroxy phenylselenoglycosides with DAST led to 2-phenylselenoglycosyl fluorides which reacted with carbohydrate acceptors to afford, stereoselectively, 2-phenylselenoglycosides. The latter compounds could be reductively deselenated to 2-deoxy glycosides or oxidatively converted to orthoesters via the corresponding ketene acetals.

Aminoglycosides↗
PubMed2001

The effect of air-drying on glycosidically bound volatiles from seasonally collected origano (Origanum vulgare ssp. hirtum) from Croatia.

The glycosidically bound volatiles were isolated from fresh and airdried origano by exhaustive percolation with ethyl acetate. After the purification of glycosidic fraction, the enzymatic hydrolysis with beta-glucosidase was performed. The obtained aglycones were analysed by GC-MS. Eighteen compounds were identified. The seasonal variations of main aglycone contents from the fresh plant material were: thymoquinone (3.10-6.18 mg/kg), benzyl alcohol (1.33-3.62 mg/kg), 3,5,5-trimethyl-4-(3-hydroxy-1-buthenyl)-2-cyclohexen-1-on (0.51-3.35 mg/kg), 2-phenyl ethanol (0.42-2.98 mg/kg), eugenol (0.93-2.55 mg/kg), thymol (0.70-1.40 mg/kg) and carvacrol (0.88-1.40 mg/kg). The season of collecting influenced the content and composition of the glycosidically bound volatiles of origano. Air-drying effected mostly the yield of these compounds.

Acetates↗
PubMed2000

Respective bioavailability of quercetin aglycone and its glycosides in a rat model.

A large number of flavonoids, mostly O-glycosides, are found in foods of plant origin. The bound sugar moiety is known to influence their bioavailability. We examined here the effect of the nature of the sugar on the absorption of the glycosides. Four groups of rats (n = 6) received a meal containing 20 mg of quercetin equivalents supplied as aglycone, quercetin 3-glucoside, quercetin 3-rhamnoside or rutin. Plasma were hydrolysed by a beta-glucuronidase/sulfatase and analyzed by HPLC coupled to UV detection at 370 nm. Four hours after the beginning of the meal, the quercetin metabolites present in plasma were identical in all groups but their total concentrations were quite different. With pure quercetin the circulating levels were 1.7 +/- 1.8 microM, but this level was three fold higher when quercetin was supplied as quercetin 3-glucoside (33.2 +/- 3.5 microM). By contrast, the plasma concentrations of quercetin metabolites was quite low with the rutin meal (about 3 microM) and undetectable after the quercetin 3-rhamnoside meal. These data suggest that the 3-O-glucosylation improves the absorption of quercetin in the small intestine, whereas the binding of a rhamnose or of a glucose-rhamnose moiety to the aglycone markedly depressed its absorption. Additionnal experiments have shown that the higher plasma levels measured after the meal containing quercetin 3-glucoside compared to quercetin were maintained throughout a 24 hour period following the meal. In conclusion, the nature of the glycosylation markedly influences the efficiency of quercetin absorption in rats. Quercetin 3-glucose can be absorbed in the small intestine and is better absorbed than quercetin itself. By contrast, glycosides containing a rhamnose moiety could not be absorbed in the small intestine.

Animals↗
PubMed1986

Evaluation of positive and negative ion fast atom bombardment mass spectrometry for structural investigations on cardenolide-type cardiac glycosides.

Evaluation of positive and negative ion fast atom bombardment (FAB) mass spectrometry for structural investigations have been studied on 30 cardiac glycosides in comparison with their field desorption (FD) mass spectra. FD mass spectra showed the prominent molecular cluster ions and the same protonation induced fragments as that established for steroid oligoglycosides. Even if the molecular cluster ions of some di- and triglycosides were hardly detected in the positive ion FAB mass spectra owing to their low intensities, a dramatic improvement was observed when sodium chloride or potassium iodide was added to the glycerol matrix. Furthermore, the prominent molecular ion species, [M-H]-, and the sequence of glycosidic linkage were easily detected in the negative mode. The combination of positive and negative ion FAB mass spectrometry of the cardenolide-type cardiac glycosides provides useful information concerning the molecular weight as well as the structures of both aglycone and sugar moieties.

Cardenolides↗
PubMed2006

Cytotoxic sulfated triterpene glycosides from the sea cucumber Pseudocolochirus violaceus.

Bioassay-guided fractionation of the active BuOH extract of the sea cucumber Pseudocolochirus violaceus resulted in the isolation of three new sulfated triterpene glycosides, i.e., violaceusides I, II, and III (1-3, resp.), as active compounds causing morphological abnormality of Pyricularia oryzae mycelia. Their structures were elucidated by spectroscopic methods including 2D-NMR and MS experiments, as well as chemical evidence. Compounds 1-3 exhibit the same structural features, i.e., the presence of a 16-oxo group in the holostane-type triterpene aglycone with the C(7)=C(8) bond, but differ in the side chains and the tetrasaccharide moieties. Compound 1 possesses one sulfate group, while 2 and 3 are disulfated glycosides. All the glycosides showed significant in vitro cytotoxicities against human gastric cancer MKN-45 and human colon cancer HCT-116 cells.

Animals↗
PubMed2003

Orthoesters versus 2-O-acyl glycosides as glycosyl donors: theorectical and experimental studies.

n-Pentenyl orthoesters (NPOEs) undergo routine acid catalyzed rearrangement into 2-O-acyl n-pentenyl glycosides (NPGs). The reactant and product can both function as glycosyl donors affording 1,2-trans linked glycosides predominantly. However, both donors differ in their rates of reactions, the yields they produce, and the nature of their byproducts, indicating that the NPOE/NPG pair may not be reacting through the same intermediates. We have therefore applied quantum chemical calculations using DFT methods and MP second order perturbation theory to learn more about orthoesters and their 2-O-acyl glycosidic counterparts. The calculations show that in the case of a manno NPG and NPOE pair, each donor goes initially to a different cationic intermediate. Thus, the former goes to a high-energy oxocarbenium ion before descending to a trioxolenium ion in which the charge is distributed over the pyrano ring oxygen, as well as the carbonyl and ether oxygen atoms of the putative C2 ester. On the other hand, ionization of the NPOE produces a dioxolenium ion lying slightly above the more stable trioxolenium counterpart. For the gluco pair, the NPG also goes to a very high-energy oxocarbenium ion, which also descends to a trioxolenium ion. However, unlike the manno analogue, the gluco NPOE does not give a dioxolenium ion; indeed, the dioxolenium is not energetically distinguishable from the trioxolenium counterpart. The theoretical observations have been tested experimentally. Thus, it was found that with manno derivatives, the orthoester is a more reactive donor than the corresponding NPG donor, whereas, for gluco derivatives, there is no advantage to using one over the other, unless one resorts to carefully selected promoters.

Acylation↗
PubMed2005

Antioxidative effects of flavonols and their glycosides against the free-radical-induced peroxidation of linoleic acid in solution and in micelles.

The antioxidative effect of flavonols and their glycosides against the peroxidation of linoleic acid has been studied in homogeneous solution (tBuOH/H(2)O, 3:2) and in sodium dodecyl sulfate and cetyl trimethylammonium bromide micelles. The peroxidation was initiated thermally by the water-soluble initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and the reaction kinetics were studied by monitoring the formation of linoleic acid hydroperoxides. The synergistic antioxidant effect of the flavonols with alpha-tocopherol (vitamin E) was also studied by following the decay kinetics of alpha-tocopherol and the alpha-tocopheroxyl radical. Kinetic analysis of the antioxidative process demonstrates that the flavonols are effective antioxidants in solution and in micelles, either alone or in combination with alpha-tocopherol. The antioxidative action involves trapping the initiating radicals in solution or in the bulk-water phase of the micelles, trapping the propagating lipid peroxyl radicals on the surface of the micelles, and regenerating alpha-tocopherol by reducing the alpha-tocopheroxyl radical. It was found that the antioxidant activity of the flavonols and their glycosides depends significantly on the position and number of the hydroxy groups, the oxidation potential of the molecule, and the reaction medium. The flavonols bearing ortho-dihydroxy groups possess significantly higher antioxidative activity than those without such functionalities, and the glycosides are less active than their parent aglycones. The activity of the flavonols is higher in micelles than in solution, while the activity of alpha-tocopherol is lower in micelles than in solution. This is because the predominant factor for controlling the activity is the hydrogen-bonding interaction of the antioxidant with the micellar surface in the case of hydrophilic flavonols, while it is the inter- and intramicellar diffusion in the case of lipophilic alpha-tocopherol.

Antioxidants↗
PubMed1995

Fate in humans of dietary intake of cyanogenic glycosides from roots of sweet cassava consumed in Cuba.

We studied if consumption of boiled fresh roots from sweet cassava varieties grown in Cuba resulted in exposure to cyanogenic glycosides and their final breakdown product, cyanide. When adult, nonsmoking subjects consumed 1-4 kg cassava over 2 days, their urinary levels of the main cyanide metabolite, thiocyanate, only increased from a mean +/- SEM of 12 +/- 2 to 22 +/- 2 mumol/l, indicating a negligible cyanide exposure. Their mean urinary linamarin, the main cyanogenic glucoside in cassava, increased from 2 +/- 1 to 68 +/- 16 mumol/l. In a second experiment 5 subjects consumed one meal of 0.5 kg boiled cassava that contained 105 mumol linamarin and 8 mumol hydrogen cyanide (HCN). Quantitative urine collections prior to and after intake showed that 28% of linamarin was excreted during the following 24 hours, whereas a modest increase of urinary thiocyanate (SCN) only corresponded to the small amount of free HCN ingested. These results indicate that the dominant cyanogen in boiled cassava is glycosides that pass through the human body without causing cyanide exposure. It remains to be studied whether humans occasionally possess intestinal or tissue beta-glucosidases that can hydrolyse cyanogenic glycosides from cassava.

Adult↗
PubMedDate not supplied

Detection of isorhamnetin glycosides in extracts of apples (Malus domestica cv. "Brettacher") by HPLC-PDA and HPLC-APCI-MS/MS.

Extracts of apple fruits (Malus domestica cv. "Brettacher") were analysed by HPLC with photodiode array detection. An unknown peak was monitored displaying the same retention time as isorhamnetin 3-O-glucoside. Preliminary identification of the isorhamnetin aglycone was performed by comparison of UV spectral data of the unknown compound with a reference substance. Using atmospheric pressure chemical ionisation mass spectrometry in the negative ion mode, the presence of an isorhamnetin glycoside was supported by loss of 162 amu from the pseudomolecular ion (m/z 477). MS2 product ion analysis of the parent ion m/z 477 provided a fragmentation pattern identical to the reference. Collision-induced dissociation of the aglycone (m/z 315) in the MS3 product ion analysis allowed the differentiation of rhamnetin and isorhamnetin, and unambiguous assignment by comparison with standard compounds. A second isorhamnetin glycoside eluting prior to the glucoside was tentatively identified as isorhamnetin 3-O-galactoside. To the best of our knowledge, this is the first report of isorhamnetin glycosides in apple fruit extracts. Results are discussed with respect to chemotaxonomic relevance within the genera Malus and Pyrus, and especially in consideration of the control of the authenticity of apple products.

Atmospheric Pressure↗