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PubMed1995

Liquid chromatography combined with thermospray and continuous-flow fast atom bombardment mass spectrometry of glycosides in crude plant extracts.

In crude plant extracts, constituents of biological or pharmaceutical interest often exist in the form of glycosides. Off-line mass spectral investigations of these metabolites require soft ionisation techniques such as desorption chemical ionisation (DCI) or fast atom bombardment (FAB) if information on molecular mass or sugar sequence is desired. In LC-MS, glycosides can be ionised by using thermospray (TSP), continuous-flow fast atom bombardment (CF-FAB) or other interfaces. These techniques are thus potentially applicable to the on-line analysis of glycosides and can be applied to plant extract analysis. Thermospray (TSP) used with ammonium acetate as buffer provides mass spectra similar to those obtained with DCI-MS using NH3 and is potentially applicable to the on-line analysis of relatively small glycosides bearing no more than three sugar units. CF-FAB provides cleaner MS spectra than static FAB due to the lower concentration of the matrix used and can be applied to more polar compounds such as glycosides with a larger number of sugars. The use of a special setup involving post-column addition of the buffer or the matrix and splitting allows LC-UV, TSP LC-MS and CF-FAB LC-MS to be performed with the same standard HPLC conditions. Different crude plant extracts containing various types of glycosides with one to eight sugar units have been analysed by both TSP and CF-FAB. Cardenolides from Nerium odorum (Apocynaceae) and saponins from Swarzia madagascariensis (Leguminosae), Aster scaber and Aster tataricus (Asteraceae) have been studied by LC-MS. The combination of these two interfaces for the HPLC screening of crude plant extracts is discussed.

Cardenolides↗
PubMed1989

Inhibition of rat brain Na+-K+-ATPase by triterpene glycosides from holothurians.

The effect of triterpene glycosides from holothurians on Na+-K+-ATPase of rat brain was investigated. The marine glycosides are irreversible inhibitors of the enzyme with an average I50 value of 10(-4) M. ATP had a low protective effect against inhibition. The inhibitory effect was increased by preincubation with MgCl2. There was alteration of the activation curve of Na+-K+-ATPase by NaCl and KCl in the presence of glycosides. Triterpene glycosides inhibited the K+-phosphatase activity, but to a smaller degree than the ATPase activity. Na+-K+-ATPase of pig kidney was less sensitive to the marine triterpene glycosides than the brain enzyme. The marine glycosides did not alter the specific binding of [3H]-ouabain to the Na+-K+-ATPase.

Adenosine Triphosphate↗
PubMed1989

Physicochemical characteristics of interaction of toxic triterpene glycosides from holothurians with rat brain Na+-K+-ATPase.

High-angle X-ray diffraction spectra showed that triterpene glycosides form crystalline complexes with membrane cholesterol. Electron microscopy demonstrated a decreased vesicle size, of the membrane preparation from rat brain which is enriched in Na+-K+-ATPase, by the triterpene glycosides. The Arrhenius plot was linear in the presence of triterpene glycosides. The half-width of the phosphatidylcholine N-methyl proton line in proton NMR spectra was not altered in the presence of marine glycosides. The excimer formation of pyrene, a hydrophobic fluorescent probe, was significantly decreased by triterpene glycosides. The increase of tryptophanyl residue fluorescence demonstrated a change of the Na+-K+-ATPase conformation after treatment with cytotoxic glycosides.

Animals↗
PubMed2002

Cyanohydrin glycosides of Passiflora: distribution pattern, a saturated cyclopentane derivative from P. guatemalensis, and formation of pseudocyanogenic alpha-hydroxyamides as isolation artefacts.

Nineteen species of Passiflora (Passifloraceae) were examined for the presence of cyanogenic glycosides. Passibiflorin, a bisglycoside containing the 6-deoxy-beta-D-gulopyranosyl residue, was isolated from P. apetala, P. biflora, P. cuneata, P. indecora, P. murucuja and P. perfoliata. In some cases this glycoside co-occurs with simple beta-D-glucopyranosides: tetraphyllin A, deidaclin, tetraphyllin B, volkenin, epivolkenin and taraktophyllin. P. citrina contains passicapsin, a rare glycoside with the 2,6-dideoxy-beta-D-xylo-hexopyranosyl moiety, while P. herbertiana contains tetraphyllin A, deidaclin, epivolkenin and taraktophyllin, P. discophora tetraphyllin B and volkenin, and P. x violacea tetraphyllin B sulfate. The remaining species were noncyanogenic. The glycosides were identified by 1H and 13C NMR spectroscopy following isolation by reversed-phase preparative HPLC. From P. guatemalensis, a new glucoside named passiguatemalin was isolated and identified as a 1-(beta-D-glucopyranosyloxy)-2,3-dihydroxycyclopentane-1-carbonitrile. An isomeric glycoside was prepared by catalytic hydrogenation of gynocardin. alpha-Hydroxyamides corresponding to the cyanogenic glycosides were isolated from several Passiflora species. These alpha-hydroxyamides, presumably formed during processing of the plant material, behave as cyanogenic compounds when treated with commercial Helix pomatia crude enzyme preparation. Thus, the enzyme preparation appears to contain an amide dehydratase, which converts alpha-hydroxyamides to cyanohydrins that liberate cyanide; this finding is of interest in connection with analysis of plant tissues and extracts using Helix pomatia enzymes.

Amides↗
PubMedDate not supplied

Perspectives for the industrial enzymatic production of glycosides.

Glycosides are of commercial interest for industry in general and specifically for the pharmaceutical and food industry. Currently chemical preparation of glycosides will not meet EC food regulations, and therefore chemical preparation of glycosides is not applicable in the food industry. Thus, enzyme-catalyzed reactions are a good alternative. However, until now the low yields obtained by enzymatic methods prevent the production of glycosides on a commercial scale. Therefore, high yields should be established by a combination of optimum reaction conditions and continuous removal of the product. Unfortunately, a bioreactor for the commercial scale production of glycosides is not available. The aim of this article is to discuss the literature with respect to enzymatic production of glycosides and the design of an industrially viable bioreactor system.

Bioreactors↗
PubMed1999

Flavonol glycosides from Montcalm dark red kidney bean: implications for the genetics of seed coat color in Phaseolus vulgaris L.

Three flavonol glycosides were isolated and identified from the commercial dark red kidney bean (Phaseolus vulgaris L.) cultivar Montcalm. In order of highest to lowest concentration these compounds were 3',4',5,7-tetrahydroxyflavonol 3-O-beta-D-glucopyranosyl (2-->1) O-beta-D-xylopyranoside (compound 1), quercetin 3-O-beta-D-glucopyranoside (compound 2), and kaempferol 3-O-beta-D-glucopyranoside (compound 3). Compound 1 is a flavonol glycoside that has not been reported before in P. vulgaris L. These three flavonol glycosides were yellow compounds that do not contribute to the garnet red color of Montcalm seed coats. Red-colored compounds which tested positive for proanthocyanidins are most likely responsible for the red seed coat color of Montcalm. Previous work on the chemistry of the compounds produced from the multi-allelic seed coat gene series C-C(r)()-c(u) indicated that neither anthocyanins nor flavonol glycosides were detected from seed coat extracts in the presence of the c(u)() locus. However, the seed coat color genotype of Montcalm is c(u) J g B v rk(d) and three flavonol glycosides were found. Technological advances such as modern HPLC analysis of seed coat extracts may allow for detection of small amounts of compounds which previously could not be seen using paper chromatography. Alternatively, the change of the Rk allele to rk(d) may allow for the synthesis of flavonol glycosides in the presence of c(u).

Chromatography, High Pressure Liquid↗
PubMed2002

Steroidal glycosides from the leaves of Cestrum nocturnum.

Further phytochemical analysis aimed at the steroidal glycoside constituents of the leaves of Cestrum nocturnum has resulted in the isolation of eight new steroidal glycosides (1-8), which were classified into a spirostanol saponin (1), a furostanol saponin (2), a pseudo-furostanol saponin (3), two pregnane glycosides (4, 5), two cholestane glycosides (6, 7), and pregnane-carboxylic acid gamma-lactone glycoside (8), and of two known spirostanol glycosides (9, 10). The structures of the new compounds were elucidated on the basis of chemical and spectroscopic evidence.

Acetylation↗
PubMed2002

Triterpene glycosides from the deep-water North-Pacific sea cucumber Synallactes nozawai Mitsukuri.

Five non-sulfated triterpene glycosides, synallactosides A(1) (1), A(2) (2), B(1) (3), B(2) (4), and C (5), have been isolated from the sea cucumber Synallactes nozawai. Their structures have been deduced by extensive analysis of NMR and mass spectra. The glycosides 2-5 are new glycosides. Glycosides 2-4 have carbohydrate chains without precedent in the glycosides from sea cucumbers. This is the first time glycosides are found in members of the family Synallactidae.

Animals↗
PubMed2000

Lectin-mediated drug targeting: selection of valency, sugar type (Gal/Lac), and spacer length for cluster glycosides as parameters to distinguish ligand binding to C-type asialoglycoprotein receptors and galectins.

PURPOSE: Common oligosaccharides of cellular glycoconjugates are ligands for more than one type of endogenous lectin. Overlapping specificities to beta-galactosides of C-type lectins and galectins can reduce target selectivity of carbohydrate-ligand-dependent drug targeting. The purpose of this study is to explore distinct features of ligand presentation and structure for design of cluster glycosides to distinguish between asialoglycoprotein-specific (C-type) lectins and galectins. METHODS: Extent of binding of labeled sugar receptors to two types of matrix-immobilized (neo)glycoproteins and to cells was evaluated in the absence and presence of competitive inhibitors. This panel comprised synthetic mono-, bi-, and trivalent glycosides with two spacer lengths and galactose or lactose as ligand part. RESULTS: In contrast to C-type lectins of hepatocytes and macrophages, bi- and trivalent glycosides do not yield a notable glycoside cluster effect for galectins-1 and -3. Also, these Ca2+-independent galactoside-binding proteins prefer to home in on lactose-bearing glycosides relative to galactose as ligand, while spacer length requirements were rather similar. CONCLUSIONS: Trivalent cluster glycosides with Gal/GalNAc as ligand markedly distinguish between C-type lectins and galectins. Undesired side reactivities to galectins for C-type lectin drug delivery will thus be minimal.

Asialoglycoproteins↗
PubMed1997

Synthesis of glycosides in which the aglycon is an N-(hydroxymethyl)amino-1,3,5-triazine derivative.

The synthesis of analogues of the anti-tumour drug 2-[N-(hydroxymethyl)methylamino]-4,6-bis(dimethylamino)-1,3,5-triazine (HMPMM) in which the OH or a dimethylamino group is replaced by a carbohydrate has been explored. Triazinyl beta-glycosides were readily prepared by reaction of sugars with trimethyl-triazinylammonium salts. These were made with one or two methylamino groups on the triazine for reaction with formaldehyde to give the cytotoxic NMeCH2OH group. However, reaction of the triazinyl glycosides with formaldehyde gave complex intractable mixtures. When the carbohydrate portion was changed to the fully protected 2,3,4,6-tetra-O-acetyl glucose a good yield of the 2-[N-(hydroxymethyl)methylamino]-4-(dimethylamino)-1,3,5-triazin-2 -yl tetra-O-acetyl beta-glucoside was obtained. However, de-acetylation using sodium methoxide also removed the N-CH2OH group. We are investigating protection of the base-sensitive N-CH2OH group as trialkylsilyl and benzyl ethers and are looking at de-acetylation methods that are more selective. We have prepared glycosides in which the sugar is joined through the oxygen of the NMeCH2OH group. Coupling of acetobromoglucose with HMPMM catalysed by silver salts was not successful. Although methyl and cyclohexyl derivatives of HMPMM may be produced in high yields by reaction of HMPMM with methyl and cyclohexyl alcohols under acidic catalysis, production of glycosides in this way gave poor yields. MNDO calculations on reactions of HMPMM helped us devise improved reaction conditions for the condensation of 2,3,4,6-tetra-O-acetyl glucose with HMPMM and its derivatives. The best procedure to generate one of the target glycosides is to react 2,3,4,6-tetra-O-acetyl glucose and formaldehyde with 2-methylamino-4,6-bis(dimethylamino)-1,3,5-triazine. The beta-glycoside product was de-acetylated using potassium carbonate in dry methanol.

Acetylation↗
PubMed2002

Systemic, genotype-specific induction of two herbivore-deterrent iridoid glycosides in Plantago lanceolata L. in response to fungal infection by Diaporthe adunca (Rob.) Niessel.

Iridoid glycosides are a group of terpenoid secondary plant compounds known to deter generalist insect herbivores. In ribwort plantain (Plantago lanceolata), the iridoid glycosides aucubin and catalpol can be induced following damage by insect herbivores. In this study, we investigated whether the same compounds can be induced following infection by the fungal pathogen Diaporthe adunca, the causal agent of a stalk disease in P. lanceolata. Significant induction of aucubin and catalpol was observed in two of the three plant genotypes used in this study following inoculation with the pathogen. In one of the genotypes, induction occurred within 6 hr after inoculation, and no decay was observed within 8 days. The highest level of induction was observed in reproductive tissues (spikes and stalks) where infection took place. In these tissues, iridoid glycoside levels in infected plants were, on average, 97% and 37% higher than the constitutive levels in the corresponding control plants, respectively. Significant induction was also observed in leaves (24%) and roots (17%). In addition to significant genotypic variation in the level of induction, we found genetic variation for the tissue-specific pattern of induction, further broadening the scope for evolutionary fine-tuning of induced responses. Recent studies have revealed a negative association between iridoid glycoside levels in P. lanceolata genotypes and the amount of growth and reproduction of D. adunca that these genotypes support. However, for the three genotypes used in the present study, differences in resistance were not related to their constitutive or induced levels of iridoid glycosides, suggesting that additional resistance mechanisms are important in this host-pathogen system. We conclude that iridoid glycosides in P. lanceolata can be induced both by arthropods and pathogenic micro-organisms. Pathogen infection could, therefore, potentially enhance resistance to generalist insect herbivores in this species.

Adaptation, Physiological↗
PubMed1998

A specific binding protein for cardiac glycosides exists in bovine serum.

Searching for a binding protein in blood, which may be involved in the specific transport of cardiac glycosides to their receptor sites on the sodium pump, we isolated a cardiac glycoside-binding protein (CGBG) of 26 kDa from the globulin fraction of bovine serum by affinity chromatography and on a ouabain-Sepharose 4B column by a purification factor of 5000. The cardiac glycoside-binding globulin was labeled specifically and covalently by the protein-reactive digoxigenin derivative HDMA (N-hydroxysuccimidyldigoxigenin-3-O-methylcarbonyl-epsilon-+ ++aminocapro ate). Even very high concentrations of other steroids, such as estrogen, testosterone, progesterone, and cortisone, did not prevent HDMA-labeling (at 5 and 100 nM) of CGBG, but the cardenolides ouabain and digoxin or the bufadienolide proscillaridin A did so. CGBG is a homodimer of two 26-kDa subunits forming disulfide bonds, since HDMA labeling of a protein of 53 kDa was observed in SDS-polyacrylamide gel electrophoresis when beta-mercaptoethanol was absent during SDS denaturation. The N-terminal amino acid sequence K-D-V-Y-R-A-P-D-G-T-Q-S-A showed no sequence similarity with proteins recorded in gene and protein sequence data banks. A 90-kDa cytosolic CGBG exists in bovine kidneys and reacts with antibodies against CGBG. Binding of ouabain to the cardiac glycoside-binding globulin was monitored by quenching of intrinsic tryptophan fluorescence. Such studies reveal two negatively cooperative ouabain binding sites with Kd' of 1.52 nM and Kd' = 75 nM and with an interaction factor of 50 using a Koshland-Némethy-Filmer model. The demonstration of a cardiac glycoside-binding globulin in plasma is consistent with the recent finding of endogenous cardiac glycosides in mammals.

Affinity Labels↗
PubMed1985

Use of cardiac glycosides in Finland.

The prevalence and number of persons receiving cardiac glycosides were estimated in connection with a general health survey. A population sample (n = 8000) representative of the adult Finnish population was studied. According to a questionnaire and an interview, about 10% of men and 11% of women were receiving cardiac glycosides. The total number of glycoside users in Finland was estimated at 311 000 (95% confidence limits 289 000-333 000). A significant serum digitalis concentration definitely indicating digitalis use was observed in about 9% of men and 10% of women. By this method the minimum number of persons receiving digitalis therapy was estimated at 248 000 (95% confidence limits 227 000-269 000). About 90% of all glycoside consumption appeared to take place outside institutions. The prevalence of glycoside use increased greatly with advancing age and tended to be higher in women than in men. The prevalence varied significantly between regions within the country. Further research is required to explain the unusually prevalent and geographically variable use of cardiac glycosides in Finland.

Adult↗
PubMed1970

The uptake of cardiac glycosides by intestinal smooth muscle of the guinea-pig in relation to digitalis receptors.

1. The accumulation and release of (3)H-digitoxin, (3)H-digoxin and (3)H-ouabain by isolated guinea-pig intestinal smooth muscle has been studied and compared with a pharmacological action due to inhibition of the sodium pump.2. The uptake of labelled cardiac glycosides can be described by means of an exponential function. The t of uptake was similar for the three compounds and did not depend on the concentration.3. Analysis of the curve relating the uptake of cardiac glycosides at equilibrium to the bath concentration enabled a non-saturable and a saturable binding site to be distinguished.4. In contrast to the uptake observations, the onset of the pharmacological effect was dependent on the concentration, and furthermore the t((1/2)) for this effect was shorter.5. The release of cardiac glycosides proceeded more slowly than the uptake.6. The uptake of a labelled glycoside was reduced in the presence of another glycoside. The amount of displaceable glycoside was nearly equivalent to the capacity of the saturable binding site.7. The significance of these results is discussed.

Animals↗
PubMed2002

Activation of cardiac ryanodine receptors by cardiac glycosides.

This study investigated the effects of cardiac glycosides on single-channel activity of the cardiac sarcoplasmic reticulum (SR) Ca2+ release channels or ryanodine receptor (RyR2) channels and how this action might contribute to their inotropic and/or toxic actions. Heavy SR vesicles isolated from canine left ventricle were fused with artificial planar lipid bilayers to measure single RyR2 channel activity. Digoxin and actodigin increased single-channel activity at low concentrations normally associated with therapeutic plasma levels, yielding a 50% of maximal effect of approximately 0.2 nM for each agent. Channel activation by glycosides did not require MgATP and occurred only when digoxin was applied to the cytoplasmic side of the channel. Similar results were obtained in human RyR2 channels; however, neither the crude skeletal nor the purified cardiac channel was activated by glycosides. Channel activation was dependent on [Ca2+] on the luminal side of the bilayer with maximal stimulation occurring between 0.3 and 10 mM. Rat RyR2 channels were activated by digoxin only at 1 microM, consistent with the lower sensitivity to glycosides in rat heart. These results suggest a model in which RyR2 channel activation by digoxin occurs only when luminal [Ca2+] was increased above 300 microM (in the physiological range). Consequently, increasing SR load (by Na+ pump inhibition) serves to amplify SR release by promoting direct RyR2 channel activation via a luminal Ca2+-sensitive mechanism. This high-affinity effect of glycosides could contribute to increased SR Ca2+ release and might play a role in the inotropic and/or toxic actions of glycosides in vivo.

Animals↗
PubMed2006

Cardiac glycosides initiate Apo2L/TRAIL-induced apoptosis in non-small cell lung cancer cells by up-regulation of death receptors 4 and 5.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (Apo2L/TRAIL) belongs to the TNF family known to transduce their death signals via cell membrane receptors. Because it has been shown that Apo2L/TRAIL induces apoptosis in tumor cells without or little toxicity to normal cells, this cytokine became of special interest for cancer research. Unfortunately, cancer cells are often resistant to Apo2L/TRAIL-induced apoptosis; however, this can be at least partially negotiated by parallel treatment with other substances, such as chemotherapeutic agents. Here, we report that cardiac glycosides, which have been used for the treatment of cardiac failure for many years, sensitize lung cancer cells but not normal human peripheral blood mononuclear cells to Apo2L/TRAIL-induced apoptosis. Sensitization to Apo2L/TRAIL mediated by cardiac glycosides was accompanied by up-regulation of death receptors 4 (DR4) and 5 (DR5) on both RNA and protein levels. The use of small interfering RNA revealed that up-regulation of death receptors is essential for the demonstrated augmentation of apoptosis. Blocking of up-regulation of DR4 and DR5 alone significantly reduced cell death after combined treatment with cardiac glycosides and Apo2L/TRAIL. Combined silencing of DR4 and DR5 abrogated the ability of cardiac glycosides and Apo2L/TRAIL to induce apoptosis in an additive manner. To our knowledge, this is the first demonstration that glycosides up-regulate DR4 and DR5, thereby reverting the resistance of lung cancer cells to Apo2/TRAIL-induced apoptosis. Our data suggest that the combination of Apo2L/TRAIL and cardiac glycosides may be a new interesting anticancer treatment strategy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

Flavonoid glycosides inhibit oral cancer cell proliferation--role of cellular uptake and hydrolysis to the aglycones.

Epidemiologic evidence supports the view that dietary flavonoids exert protective effects in oral diseases, including cancer. However, the dietary forms of flavonoids, the flavonoid glycosides, are thought to be inactive, thus they must first be hydrolysed to their active aglycones. This may occur in the saliva in the oral cavity. We have examined if the flavonoid glycosides directly could affect cell proliferation, using the human oral squamous carcinoma SCC-9 cells. The cellular uptake and hydrolysis of the glycosides were assessed also. The four flavonoid glycosides tested each behaved differently. Genistin, the 7-glucoside of genistein, showed clear and consistent inhibition of cell proliferation, which appeared to be the result of rapid cellular uptake of the glucoside and hydrolysis to genistein. Spiraeoside, the 4'-glucoside of quercetin, showed a similar inhibition of cell proliferation, which also appeared to be associated with its hydrolysis to quercetin. Diosmin, the 7-rutinoside of diosmetin, surprisingly, was more potent and effective than diosmetin. In contrast, quercitrin, the 3-rhamnoside of quercetin, showed no effect and only minimal cellular uptake and no hydrolysis. In summary, dietary flavonoid glycosides may exert cellular effects in the oral cavity, but this varies greatly with the nature of the glycoside.

Carcinoma, Squamous Cell↗
PubMed1992

3 beta-Hydroxysialic acid glycosides. I. Calcium-binding ability and chemical and enzymatic stabilities.

Methyl alpha- and beta-glycosides of N-acetylneuraminic acid (Neu5Ac) and N-acetyl-3 beta-hydroxyneuraminic acid (Neu5Ac beta 3OH) (1-4) were prepared to evaluate their calcium-binding ability. (Methyl alpha-glucopyranosidonyl) alpha- and beta-, and 4-methylumbelliferyl alpha-glycosides of Neu5Ac and Neu5Ac beta 3OH (5-10) were also synthesized for the comparison of chemical and enzymatic stabilities, respectively. Methyl beta-glycosides of Neu5Ac and Neu5Ac beta 3OH, 3 and 4, respectively, showed intense calcium-binding abilities, while no such ability was observed in the corresponding alpha-glycosides, 1 and 2. The Neu5Ac beta 3OH glycosides, 6, 8, and 10, showed much stronger resistance to acidic hydrolysis and sialidase digestion than the corresponding Neu5Ac glycosides, 5, 7, and 9.

Animals↗