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PubMed1983

[Role of sterols in the membranotropic activity of triterpene glycosides].

Interaction of stichoposide A, a triterpene glycoside and trepang sterols in solution was studied. With the use of liposomes the binding of the glycoside and its effect on the ion permeability of the lipid membranes of different sterol composition were also studied. It was shown that the membrane activity of the glycoside was defined by the level of its affinity to the sterol receptor. It decreased in the following order: cholesterol, total fraction of delta 5-sterols, total fraction of delta 7-sterols, delta 7-sterol xylosides and delta 5-sterol sulfates. Possible involvement of glycosylated and sulfated forms of sterols in development of resistance in the cell membranes and tissues of trepangs to their own glycosides is discussed.

Animals↗
PubMedDate not supplied

[Effect of triterpene glycosides and polyene antibiotics on cell membrane permeability for K+ ions and UV-absorbing substances].

The effect of triterpene glycosides (cauloside C from Caulophyllum robustum, theasaponine from Thea sinensis, cucumarioside G from Cucumaria fraudatrix stichoposide A from Stichopus japonicus S., holothurines A and B from Holothuria mexicana, holothurine C from Bohadschia sp.) on the membrane permeability for K+ ions and UV-absorbing substances was compared with that of polyene antibiotics, viz., amphotericine B and nystatine. As a biological model fertilized eggs of sea urchin Strongylocentrotus nudus and yeast Saccharomyces carlsbergensis were used. In the sea urchin study most triterpene glycosides in low concentrations induced the outflux of K+ and in hgih concentrations that of both K+ and UV-absorbing agents. In the yeast study triterpene glycosides at identical doses induced the outflux of both K+ and UV-absorbing agents. The membranotropic effect of triterpene glycosides depended on the medium temperature and the biological system used.

Anti-Bacterial Agents↗
PubMed1980

Sodium dependence of the positive inotropic effect of cardiac glycosides.

We have investigated the inotropic effects of digoxin, digitoxin and ouabain in cat ventricular muscle under conditions of reduced Na influx in an effort to determine the role of Na in the positive inotropic effect of these cardiac glycosides. When the normal, Na-dependent action potential is inactivated by potassium depolarization, these glycosides retain a positive inotropic effect. In contrast, when muscles are bathed in Na-poor or Na-free solutions, these glycosides do not influence contraction. This suggests that the cardiac glycosides are dependent on Na for their positive inotropic effects.

Animals↗
PubMed1978

[Optimization of therapy using cardiac glycosides].

By the estimation of the serum glycoside concentration during the last years numerous new recognitions have been got, particularly concerning the pharmacokinetics of the heart glycosides, which increasingly will be reflected in the clinical practice. Apart from thoughts on pharmacokinetics the author adopts a definite attitude to glycoside tolerance, to the influence of age and bodyweight as well as to the importance of disturbances of the renal function. Moreover it is referred to new aspects in the dosage of heart glycosides, in which case the revision of the central therapy recommendations seems to be necessary.

Adult↗
PubMed1994

Identification of an amino acid substitution in human alpha 1 Na,K-ATPase which confers differentially reduced affinity for two related cardiac glycosides.

The ouabain-resistant cell line H1C1 displays a 30-fold differential of reduced sensitivity to the structurally related cardiac glycosides digoxin and digitoxin (Baker, R. M. (1976) in Biogenesis and Turnover of Membrane Macromolecules (Cook, J.S., ed) pp. 93-103, Raven Press, New York). Since these ligand congeners differ only by the presence of a hydroxyl group at C-12 of digoxin we predicted that the H1C1 phenotype must reflect a mutation which alters the binding site of the cardiac glycoside receptor (Na,K-ATPase). Complementary DNA encoding the alpha 1 Na,K-ATPase was prepared from H1C1 cell total RNA by reverse transcription-coupled polymerase chain reaction and these cDNAs were cloned. Sequence analysis of the reverse transcriptase-polymerase chain reaction clones revealed several independent isolates containing a G > A transition at nucleotide 332 of the propeptide coding sequence, generating the amino acid substitution C108Y. The ability of this substitution to confer differential sensitivity for digoxin and digitoxin was tested and confirmed by expressing a human alpha 1 C108Y-Na,K-ATPase in wild type HeLa cells and assaying for inhibition of cell growth and inhibition of Na,K-ATPase activity. Phenylalanine or alanine substitutions of this cysteine also confer this pattern of ligand discrimination. Ouabain-resistant Na,K-ATPase substitutions, at positions other than Cys-108 failed to exhibit differential sensitivity indicating that this ligand discrimination is unique to Cys-108 substitutions rather than a general property of cardiac glycoside-resistant mutants. It is proposed that differential resistance of the C108Y receptor for these ligands is a consequence of altering two features of the ligand-receptor interaction; one, a disruption of a common hydrogen bond resulting in general loss of affinity for cardiac glycosides and the other, formation of a new H-bond between the C-12 hydroxyl of digoxin and the receptor, specifically augmenting the stability of this ligand-receptor complex.

Amino Acid Sequence↗
PubMed1994

[Inhibitory effects of 6 cardiac glycosides on sodium pump in sheep Purkinje fibers].

The inhibitory effects of 6 cardiac glycosides (digoxin, meproscillarin, acrihellin, deslanoside, ouabain, K-strophanthin) on sodium pump in sheep Purkinje fibers were studied. Isolated Purkinje fibers were used and stimulated at 0.4 Hz regularly. Intracellular sodium activity (aiNa), potassium activity (aiK) and membrane potential (Em) were monitored with single barrel normal and ion-selective micro-electrodes. It was shown that aiNa rose definitely from the concentration of 30 nmol.L-1, and became more significant until the dose of 0.4 mumol.L-1. aiNa rose very much faster within the range of toxic doses (from 1-20 mumol.L-1 to 1 mmol.L-1). The occurrence time of delay afterdepolarization (DAD) after adding drugs varied with various drugs used, or with different experiments, hence the time points of DAD and delta aiNa-time, concentration relation curves were quite scattered. But when basing on the appearance of DAD as a common time point we calculated the temporal variation of aiNa before and after toxic effect, the relation curves in a same sort of glycoside were kept uniform. When the toxic effects of glycosides appeared, the inhibition degree of sodium pump activity was quite close (between 52.8% and 65.5%), suggesting that there existed close relationship between sodium pump inhibition and toxic effects of glycosides. Intracellular potassium ions lost progressly within the scope of subtoxic doses (10-30 nmol.L-1) and lost more significantly within the scope of toxic doses (1-20 mumol.L-1). Based on the results of calculation, the inward current induced by the sodium pump inhibition might be responsible for the abnormal automaticity.

Animals↗
PubMed1996

Reaction of hydroxyl radical with phenylpropanoid glycosides from Pedicularis species: a pulse radiolysis study.

Using pulse radiolysis technique, the reaction between hydroxyl radical and 7 phenylpropanoid glycosides: echinacoside, verbascoside, leucosceptoside A, martynoside, pediculariosides A, M and N which were isolated from Pedicularis were examined. The rate constants of these reactions were determined by transient absorption spectra. All 7 phenylpropanoid glycosides react with hydroxyl radical at high rate constants within (0.97-1.91) x 10(10)L.mol-1.s-1, suggesting that they are effective hydroxyl radical scavengers. The results demonstrate that the numbers of phenolic hydroxyl groups of phenylpropanoid glycosides are directly related to their scavenging activities. The scavenging activities are likely related to o-dihydroxy group of phenylpropanoid glycosides as well.

Drugs, Chinese Herbal↗
PubMed1976

[Serum concentration of digitalis glycosides as a therapeutic guide].

The concentration of digitalis glycosides in serum may serve as a useful guide in adjusting digitalis glycoside dosage to individual needs. Radio-immunological determination of digoxin is mainly indicated when patients with renal failure, hypothyroidism or hyperthyroidism or elderly subjects are treated with digoxin, when signs of digitalis intoxication are present or when patient compliance has to be assessed. However, factors which alter myocardial sensitivity to digitalis glycosides must be considered in the interpretation of serum concentrations of digitalis glycosides.

Digitalis Glycosides↗
PubMed2000

Antidiabetogenic activity of oleanolic acid glycosides from medicinal foodstuffs.

Oleanolic acid glycosides from several medicinal foodstuffs were found to show potent inhibitory activity on the increase of serum glucose levels in oral glucose-loaded rats. By examination of the structure-activity relationships, the 3-O-glucuronide moiety and the 28-carboxyl group in oleanolic acid glycosides were required to exert the hypoglycemic activity. Oleanolic acid glycosides were found to have neither insulin-like nor insulin-releasing activity, but they inhibited gastric emptying and glucose-uptake in the small intestine. Investigation of the mode of action revealed that the inhibition of gastric emptying was mediated by capsaicin-sensitive sensory nerves and the central nervous system. Furthermore, oleanolic acid glycosides were suggested to suppress the gastric emptying by stimulating the release and/or production of dopamine to act through dopamine2 receptors, which in turn causes the release of prostaglandins.

Animals↗
PubMed1986

Early O-glycosidic glycosylation of proglucagon in pancreatic islets: an unusual type of prohormonal modification.

Proglucagon from rat islets is identified as a glycoprotein by its binding to soybean lectin and by the biosynthetic incorporation of [14C]galactosamine. Glycosylation can be demonstrated for both forms of proglucagon, i.e. the primary translation product which is detectable as early as 30 s after incubation of isolated islets with radioactive amino acids (proglucagon a), and its conversion product of slightly higher electrophoretic mobility which is formed after 5-10 min of incubation (proglucagon b). This glycosylation is determined to be of the O-glycosidic type by the following criteria: rat proglucagon has previously been shown to lack an acceptor sequence for N-glycosidic linkage of sugars, the sugar bond in rat proglucagon is labile under mild alkaline conditions, glycosylated serine is demonstrated in proteolytic lysates of both the early and the late form of this prohormone. O-glycosidic linkage of sugars has not been reported for other prohormones. Its early formation and the apparent absence of N-glycosidically bound sugars in proglucagon give evidence for an unusual type of protein glycosylation.

Animals↗
PubMed1995

Steviol and steviol-glycoside: glucosyltransferase activities in Stevia rebaudiana Bertoni--purification and partial characterization.

The leaves of Stevia rebaudiana Bertoni contain sweet compounds which are glycosides of diterpene derivative steviol (ent-13-hydroxykaur-16-en-19-oic acid). Its main constituents are stevioside (triglucosylated steviol; 13-O-beta-sophorosyl-19-O-beta-glucosyl-steviol) and rebaudioside-A (tetraglucosylated steviol; 2'-O-beta-glucosyl-13-O-beta-sophorosyl-19-O-beta-glucosyl-stev iol). From the extracts of S. rebaudiana Bertoni, two glucosyltransferases (GTases I and IIB) acting on steviol and steviol-glycosides were isolated, and another distinct activity (GTase IIA) acting on steviol was detected. Purified GTase I (subunit M(r) 24,600) catalyzed glucose transfer from UDP-glucose to steviol and steviolmonoside (steviol-13-O-glucopyranoside), but not to other steviol-glycosides. Apparent Km values were 71.4 microM for steviol and 360 microM for UDP-glucose. GTase IIB (subunit M(r) 30,700) showed a broad substrate specificity, acting on steviol, steviolmonoside, steviolbioside (13-O-beta-sophorosyl-steviol), and stevioside. Apparent Km values were 182 microM for steviol, 44 microM for steviolbioside, 95 microM for stevioside, and 385 microM for UDP-glucose. The two enzymes had a similar optimum pH at 6.5. They also acted effectively on ubiquitous flavonol aglycones, quercetin, and kaempferol and utilized kaempferol at a higher rate than steviol and steviol-glycosides. The apparent Km values of GTase I and IIB for kaempferol were 12 and 31 microM, respectively.

Chromatography, Gel↗
PubMed1997

Solubilization of Large Unilamellar Liposomes by Alkyl Glycosides

The study of biological membranes involves the dissociation, characterization and re-assembly of membrane components. The most important aspect of this approach is the use of an appropriate surfactant as solubilizing agent. In this work the solubilization of large unilamellar liposomes by alkyl glycosides has been studied. Solubilization of phospholipid bilayer is produced by the formation of surfactant-phospholipid mixed micelles. Some pure alkyl glycosides as well as two commercial alkyl polyglucosides have been tested. This has permitted the study of the solubilizing capacity of the phospholipidic bilayer of different alkyl glycosides as a function of their structure. Among the alkyl glycosides tested, dodecyl maltoside has shown the lowest critical micelle concentration as well as the highest solubilizing capacity, i.e., the minimal surfactant/phospholipid molar ratio in the mixed micelles.

Journal Article↗
PubMed1996

Chemistry and biological activity of triterpenoid glycosides from Medicago sativa.

Ten triterpenoid glycosides have been isolated from the roots of Medicago sativa L. (Leguminosae) including eight new glycosides and two previously known, medicagenic acid 3-O-beta-D-glucopyranoside and hederagenin 3-O-[beta-D-glucopyranosyl(1-->2)-alpha-L-arabinopyranoside]. Four new saponins were identified as glycosides of medicagenic acid, four from hederagenin. Their structures were elucidated by a combination of chemical and spectroscopic techniques (IR, EI/MS, NMR 1H and 13C). In some cases we used fast atom bombardment mass spectra (FAB/MS), NMR 1H difference spectra (homonuclear double resonance, Overhauser effect), NMR 13C partially decoupled spectra (off resonance), and two-dimensional 1H-1H correlating spectra (COSY 1H-1H). The inhibitory effects of these glycosides on growth and seed germinations and on some phytopathogenic bacteria have also been tested.

Bacteria↗
PubMed1987

The structures of N- and O-glycosidic carbohydrate chains of a chondroitin sulfate proteoglycan isolated from the media of the human aorta.

A large Mr chondroitin sulfate proteoglycan was extracted from the media of human aorta under dissociative conditions and purified by density-gradient centrifugation, ion-exchange chromatography, and gel filtration chromatography. Removal of a contaminating dermatan sulfate proteoglycan was accomplished by reduction, alkylation and rechromatography on the gel filtration column. After chondroitinase ABC treatment, the proteoglycan core was separated from a residual heparan sulfate proteoglycan by a third gel filtration chromatography step. As assessed by radioimmunoassay, the isolated proteoglycan core was free of link protein, but possessed epitopes that were recognized by antisera against the hyaluronic acid binding region of bovine cartilage proteoglycan as well as those that were weakly recognized by anti-keratan sulfate antisera. Following beta-elimination of the protein core, the liberated low Mr oligosaccharides were partially resolved by Sephadex G-50 chromatography, and their primary structure was determined by 500-MHz1H NMR spectroscopy in combination with compositional sugar analysis. The N-glycosidic carbohydrate chains, which were obtained as glycopeptides, were all biantennary glycans containing NeuAc and Fuc; microheterogeneity in the NeuAc----Gal linkage was detected in one of the branches. The N-glycosidic glycans have the following overall structure: (Formula: see text). The majority of the O-glycosidic carbohydrate chains bound to the protein core were found to be of the mucin type. They were obtained as glycopeptides and oligosaccharide alditols, and possessed the following structures: NeuAc alpha(2----3)Gal beta(1----3)GalNAc-ol, [NeuAc alpha(2----3)Gal beta(1----3)[NeuAc alpha(2----6)]GalNAc-ol, and NeuAc alpha-(2----3) Gal beta(1----3)[NeuAc alpha(2----3)Gal beta(1----4)GlcNAc beta(1----6)] GalNAc-ol. The remainder of the O-glycosidic carbohydrate chains bound to the isolated proteoglycan were the hexasaccharide link regions of the chondroitin sulfate chains that remained after chondroitinase ABC treatment of the native molecule. These latter glycans, which were obtained as oligosaccharide alditols, had the following structure (with GalNAc free of sulfate or containing sulfate bound at either C-4 or C-6): delta 4,5GlcUA beta(1----3)GalNAc beta(1----4)GlcUA beta(1----3)Gal beta(1----3)Gal beta(1----4)Xyl-ol.

Amino Acids↗
PubMed1992

The MDR1 gene product, P-glycoprotein, mediates the transport of the cardiac glycoside, digoxin.

Digoxin, a widely used cardiac glycoside with a low therapeutic index, is known to interact with a large and diverse group of co-administered drugs, frequently leading to toxic accumulation of the glycoside. Establishing the mechanism(s) of these interactions, therefore, has potential clinical significance. The present studies implicate P-glycoprotein, the MDR1 gene product overexpressed in multidrug resistant cells, as the apical membrane protein responsible for the renal secretion of digoxin and provide an explanation for the occurrence of digoxin toxicity in the presence of certain co-administered medications. Since digoxin is considered a prototype for endogenous digitalis-like glycosides, the results also allow for speculation that endogenous digitalis-like glycosides may be the natural substrates for P-gp.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1984

Synthesis from pullulan of spacer-arm, lipid, and ethyl glycosides of a tetrasaccharide [alpha-D-Glc-(1----6)-alpha-D-Glc-(1----4)-alpha-D-Glc-(1----4)-D-Glc] found in human urine; preparation of neoglycoproteins.

Enzymic hydrolysis of pullulan, followed by acetylation and chromatography, gave acetylated alpha-D-Glcp-(1----6)-alpha-D-Glcp-(1----4)-alpha-D-Glcp-(1----4)-D-Glcp which, with 2-bromoethanol and boron trifluoride etherate in dichloromethane, gave the 2-bromoethyl glycoside. The reactions of the glycoside with methyl 3- mercaptopropionate , methyl 11- mercaptoundecanoate , and octadecanethiol are described, and also its hydrogenolysis to give an ethyl glycoside. The mercaptopropionate -derived, spacer-arm glycoside has been coupled to bovine serum albumin and keyhole limpet haemocyanin.

Glucans↗
PubMed1994

NMR studies of some (1-->6)-linked disaccharide methyl glycosides.

NMR studies have been performed on the methyl glycosides of some (1-->6)-linked disaccharides. Observed J5,6pro-R and J5,6pro-S values indicate that, for the 6-substituted D-gluco- and D-galacto-pyranosides, the rotamer distribution around the C-5-C-6 bond deviates somewhat from that observed for the respective unsubstituted monosaccharide glycosides. There is also a difference between 6-O-alpha-D- or 6-O-beta-L- on the one hand and 6-O-beta-D- or 6-O-alpha-L-substituted glycosides on the other, with somewhat larger values for J5,6pro-R for the latter two indicating a higher proportion of the gauche-trans conformer. The glycosylation shifts observed for the signals from the 6-protons in the glycosidic linkage were dependent on the type of anomeric and absolute configuration of the glycosyl group. NOE measurements by irradiation of the anomeric proton indicated that sugars 6-substituted with alpha-D- or beta-L-glycosyl groups have highly populated conformations in which H-1 and H-6pro-S are proximal, and for beta-D- and alpha-L-glycosyl groups conformations in which H-1 and H-6pro-R are proximal.

Carbohydrate Conformation↗
PubMed1996

Synthesis of the methyl alpha-glycosides of a di-, tri-, and a tetra-saccharide fragment mimicking the terminus of the O-polysaccharide of Vibrio cholerae O:1, serotype Ogawa.

Methyl 4-(3-deoxy-L-glycero-tetronamido)-4,6-dideoxy-2-O-methyl-alpha-D- mannopyranoside was acetylated, and the fully protected methyl glycoside was treated with dichloromethyl methyl ether-ZnCl2 (DCMME-ZnCl2) reagent to give 3-O-acetyl-4-(2,4-di-O-acetyl-3- deoxy-L-glycero-tetronamido)-4,6-dideoxy-2-O-methyl-alpha-D-mannop yranosyl chloride (3). Condensation of 3 with methyl 3-O-acetyl-4-(2,4-di-O-acetyl-3-deoxy-L-glycero-tetronamido)-4,6- dideoxy-alpha-D-mannopyranoside (4) gave the fully acetylated disaccharide 5, which was deacetylated yielding the methyl alpha-glycoside of title disaccharide. The disaccharide glycosyl donor required for the blockwise synthesis of the title tri- and the tetra-saccharide, 3-O-acetyl-4-(2,4-di-O-acetyl-3-deoxy-L-glycero-tetronamido)-4,6-d ideoxy-2-O- methyl-alpha-D-mannopyranosyl-(1-->2)-3-O-acetyl-4- (2,4-di-O-acetyl-3-deoxy-L-glycero-tetronamido)-4,6-dideoxy-alpha- D- mannopyranosyl chloride (12), was obtained by condensation of 3 with the 1-O-acetyl analog of 4, followed by treatment of the disaccharide formed with DCMME-ZnCl2. The synthesis of the methyl alpha-glycoside of the title trisaccharide involved a condensation of 12 with 4, followed by deacetylation. Similarly, the condensation of 12 with 15, the latter being the analog of 5 having a free HO-2, followed by deacetylation, gave the methyl alpha-glycoside of the title tetrasaccharide. All glycosylation reactions were mediated by silver trifluoromethanesulfonate in the presence of 2,4,6-trimethylpyridine. 4-(3-Deoxy-L-glycero-tetronamido)-4,6-dideoxy-2-O-methyl-alpha,bet a-D- mannopyranose was prepared for the first time. It was characterized by NMR spectroscopy, and via its crystalline per-O-acetyl derivative. It is the saccharide whose alpha-form constitutes the terminal, non-reducing end-group of the O-PS of V. cholerea O:1, serotype Ogawa.

Carbohydrate Conformation↗