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The capability of digitalis glycoside-specific antisera to reverse the glycoside-induced inhibition of (Na+ + K+)-ATPase activity was examined. The antisera-induced reversal of the ATPase inhibition caused by digoxin was considerably slower (k-1 = 0.1177 . 10-3 .S-1) than the reversal caused by dihydrodigoxin and dihydrodigitoxin (k-1 = 4.462 . 10-3 . S-1 and K-1 = 3.609 .10-3 . S-1, respectively). In addition, the dissociation rate constants of the ouabain-induced dissociation of the various glycosides from the glycoside-ATPase complex were determined: The dissociation rate constants of the antisera-induced restoration of enzyme activity and that of the ouabain-induced dissociation of glycosides from the glycoside-enzyme complex were not significantly different.
This paper describes the application of thermospray-HPLC-MS (buffer ionization mode, single-stage MS, positive ion detection) to the analysis of flavanols (catechins), flavonol O-glycosides, flavone C-glycosides as well as caffeine, theobromine, theogallin and theanine from tea. All compounds are detected as pseudo-molecular ions [M+H]+. Other molecular ion species are adducts with sodium, potassium, ammonium and solvent clusters. The catechin gallates and the flavonol glycosides are fragmented. The fragmentation is temperature dependent. The glycoside bond is labile and consequently the flavonol glycosides have the protonated aglycone as this base peak. The ester bonds in the catechin gallates are more stable and the fragmentation is limited. The fragment pattern contributes to the structural information. LC-thermospray-MS is a good analytical tool for identifying the polyphenols mentioned above both in tea and other foodstuffs, especially in method development and structural elucidation.
Asclepias fruticosa afforded, in addition to five known pregnane glycosides and 11 known cardenolide glycosides, four new pregnane glycosides and eleven new cardenolide glycosides. Structures of these compounds were elucidated by spectroscopic methods and from chemical evidence.
Digitoxigenin alpha-L-, beta-L-, alpha-D-, and beta-D-glucosides; alpha-L-, beta-L-, alpha-D-, and beta-D-mannosides; and alpha-L- and beta-L-rhamnosides were stereoselectively synthesized from the corresponding sugar tetrabenzyl trichloroacetimidates. The Na+,K+-ATPase receptor inhibitory activities of these glycosides (as a measure of receptor binding) were compared with those of digitoxigenin, digitoxigenin 6'-hydroxy-beta-D-digitoxoside, digitoxigenin beta-D-galactoside, and digitoxigenin beta-D-digitoxoside. The observed activities reveal that a given sugar substituent may have a role in binding of some glycoside stereoisomers, but not others. With alpha-L- and possibly beta-L-rhamnosides, the 5'-CH3 and 4'-OH appear to have a predominant role in binding to the Na+,K+-ATPase receptor. Addition of a 6'-OH to form the corresponding mannosides dramatically disrupts the effect of both the 5'-CH3 and 4'-OH in prompting receptor binding of the alpha-L isomer. However, with the beta-L isomer, some influence of 4'-OH, 3'-OH, and 2'-OH binding remains. With beta-D-glycosides, binding via the "5'-CH3 site" appears to be of little importance and addition of a 6'-OH diminishes activity only slightly. With these beta-D-glycosides, an equatorial 4'-OH, axial 3'-OH, and equatorial 2'-OH groups appear to contribute to binding.
The tri and tetra-saccharide glycosides beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OTMSEt and beta-D-Gal-(1-3)-beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OT MSEt (asialo-GM1) have been synthesized by sequential glycosylations of a suitably protected 2-(trimethylsilyl)ethyl (TMSEt) lactoside with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl chloride and 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl bromide. The tetrasaccharide glycoside was transformed into the corresponding hemiacetal sugar as well as the 1-chloro sugar. The latter was used for glycosylation of 2-bromoethanol. The resulting glycoside was used to alkylate methyl 3-mercaptopropionate and the resulting spacer glycoside was used for the preparation of the title glycoconjugates.
The flavonoid constituents of various spices were separated by means of chromatography on cellulose colums, and the following compounds were obtained crystalline: Quercetin 3-glucuronide from caraway, fennel, anise, and coriander; isoquercitrin from caraway and fennel; rutin from fennel and anise; quercetin 3-O-caffeylglucoside and kaempferol 3-glucoside from caraway; quercetin 3-arabinoside from fennel, and luteolin 7-glucoside, isoorientin and isovitexin from anise. Other constitutents which were however not obtained crystalline, but which could be identified by the usual procedures were kaempferol 3-glucuronide and kaempferol 3-arabinoside in fennel, apigenin 7-glucoside and a luteolin glycoside in anise, and isoquercitrin and rutin in coriander. The glycosides contained in the fruit of the four spices also occur in the leaves. Leaves of caraway and fennel in addition contain isorhammetin glycosides in low concentration.
Free and glycosidically bound terpenes of five Vitis vinifera grape cultivars (muscat of Alexandria, muscat of Frontignan, muscat of Hamburg, muscat Ottonel and Gewürztraminer) were investigated. The free and bound fractions were separated by selective retention on Amberlite XAD-2 resin. The glycosidic fractions were analysed by gas chromatography and gas chromatography-mass spectrometry using either enzymic hydrolysis and subsequent analysis of the released aglycones or trimethylsilyl (TMS) and trifluoroacetyl derivatives. The known monoterpenyl, benzyl and 2-phenylethyl beta-D-glucopyranosides, beta-rutinosides, 6-O-alpha-L-arabinofuranosyl-beta-D-glucopyranosides and 6-O-beta-D-apiofuranosyl-beta-D-glucopyranosides were determined. A number of other glycosides were detected and the structures of some of them, mainly apiosylglucosides and glucosides with aglycones in higher oxidation state than linalol, were tentatively identified using the mass spectra of their TMS and TFA derivatives and the results obtained from the analysis of their aglycones.
Preparation of the following glycosides is described: 2-aminoethyl beta-D-glycosides of (A) 2-acetamido-3,4,6-trio-O-acetyl-2-deoxy-D-glucopyranose, (B) 2-acetamido-4-O-(2-acetamido-3,4,6-trio-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-beta-D-glucopyranose (N,N'-diacetylchitobiose pentaacetate), (C) 4-O-(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)-2,3,6-trio-O-acetyl-beta-D-glucopyranose (cellobiose heptaacetate); 8-carboxyoctyl glycosides of (D) cellobiose, and (E) N,N'-diacetylchitobiose. Conjugates were prepared from (A), (B), and (C) by coupling to bovine serum albumin by cyanuric trichloride and subsequent deacetylation; (D) and (E) were coupled to bovine serum albumin by the mixed-anhydride reaction. Conjugates (A) and (B) were insoluble; conjugates (C), (D), and (E) functioned as artificial antigens and gave rise to precipitating antibodies in rabbits. Specificities of the antisera were determined by inhibition studies.
p-Methoxyphenyl (pMP) beta-D-glycopyranosides (Glc, Gal, GlcNPhth, GalNPhth, GlcNTroc, Gal beta 4Glc, Gal alpha 4Gal) were prepared from the corresponding 1-O-acetyl sugars in 79-90% yield, using boron trifluoride etherate as promoter. Treatment of the pMP glycosides with acyl chlorides or bromides in the presence of various Lewis acids gave the corresponding glycosyl chlorides and bromides in 81-98% yield. Treatment of the acyl-protected pMP glycosides with thiophenol and boron trifluoride etherate gave the corresponding thioglycosides in 80-100% yield and high (> 20:1) beta/alpha selectivity. The stability of pMP glycosides was investigated against a series of reagents.
A series of digitoxigenin glycosides was studied: five with beta-D-sugars varying stepwise in sugar structure from beta-D-digitoxose to beta-D-galactose, including one beta-D/alpha-D pair. I50 values for these glycosides and digitoxigenin were determined with hog kidney Na+, K+-ATPase. These data suggest a major and unexpected role for 4'-OH conformation in the sugar. All the glycosides with an equatorial 4'-OH were more active than the two with the 4'-OH axial [digitoxigenin beta-D-galactoside (6) I50 = 6.45 X 10(-8) M; digitoxigenin 2'-deoxy-alpha-D-ribo-hexopyranoside (alpha-3a) I50 = 9.33 X 10(-8) M; digitoxigenin I50 = 1.17 X 10(-7) M]. Stereochemistry of the 3'-OH had much less of an activity role than that of the 4'-OH, in contrast to existing models of "sugar-site" binding.
Rates of acid-catalyzed solvolysis of glycoside bonds in glycosphingolipids were compared to establish a basis for conducting saccharide analysis. Permethylated globotetraosylceramide and asialogangliotriaosylceramide as model compounds for methylation and sugar composition analysis, respectively, were solvolyzed under acidic conditions and the sugar components thus obtained were determined at specified times by gas liquid chromatography, after they had been derivatized. Reducing-end glucose residues in both compounds were liberated more slowly than other sugar residues. Glycoside bonds between reducing-end glucose and ceramide in glycosphingolipids would thus appear to be more resistant towards acid-catalysed solvolysis than other glycoside bonds between hexopyranosides.
By condensation of 1,3-diamino-2,4-(R)-O-benzylidene-1,3-dideoxy-D-erythritol (3) and 1,3-diamino-2,4-di-O-benzyl-1,3-dideoxy-D-threitol (4) with methyl 2,3,6-tri-O-benzyl-4-deoxy-4-iso-thiocyanato-beta-D-glucopyranosid e (9) the (1-->4)-linked disaccharide analogues 4-deoxy-4-[(4R,5S)-5-hydroxy-4-(hydroxymethyl)-1,4,5,6-tetrahydropyri midin-2- yl[amino-alpha,beta-D-glucopyranose hydrochloride (15) and 4-deoxy-4-[(4R,5R)-5-hydroxy-4-(hydroxymethyl)-1,4,5,6-tetrahydropyri midin- 2-yl]amino-alpha,beta-D-glucopyranose hydrochloride (18) were synthesized. By the same reaction sequence, using 3 and methyl isothiocyanate, the glycoside analogue (4R,5S)-5-hydroxy-4-(hydroxymethyl)-2-methylamino-1,4,5,6- tetrahydropyrimidine hydrochloride (20) was obtained. All compounds possess in their 'glyconic' moiety the flat guanidinium group, mimicking a glucopyranosyl cation. Together with the previously synthesized (1-->6)-linked disaccharide analogues 6-deoxy-6-[(4R,5S)-5-hydroxy-4-(hydroxymethyl)-1,4,5,6- tetrahydropyrimidin-2-yl]amino-alpha,beta-D-glucopyranose hydrochloride (1) and 6-deoxy-6-[(4R,5R)-5-hydroxy-4-(hydroxy-methyl)-1,4,5,6- tetrahydropyrimidin-2-yl]amino-alpha,beta-D-glucopyranose hydrochloride (2), a possible inhibitory effect on the action of alpha-D-glucosidase, beta-D-glucosidase, alpha-D-galactosidase, and beta-D-galactosidase was investigated. All compounds, except 20 with alpha-D-glucosidase where no inhibition could be detected, showed either competitive or mixed competitive inhibition with all enzymes. The effects of the disaccharide analogues were generally weaker as compared to the effect of the previously synthesized configurationally related nitrophenyl glycoside analogues (4R,5S)-5-hydroxy-4-(hydroxymethyl)-2-(p-nitrophenyl)amino-1,4,5,6- tetrahydropyrimidine hydrochloride (21) and (4R,5R)-5-hydroxy-4-(hydroxymethyl)-2-(p-nitrophenyl)amino-1,4,5,6- tetrahydropyrimidine hydrochloride (22). On the basis of experimental results, different binding hydrochloride (22). On the basis of experimental results, different binding modes of competitive inhibitors to the active site of corresponding enzymes are discussed.
Attempted dephthalimidation of the trisaccharide 1-O-acetyl-3,4-di-O-benzyl- 2,6-di-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl )-alpha-D-mannopyranose (1) and its derivatives 2 and 3, as well as the disaccharide 1-O-acetyl-3,4,6-tri-O-benzyl-2-O-(3,4,6-tri-O-acetyl- 2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-alpha-D-mannopyranose (13), with hydrazine hydrate in ethanol at 80 degrees C, produced the trisaccharide-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D- glucopyranosyl)-3,4-di-O-benzyl-beta-D-mannopyranose-3',4',6'-tri-O-a cet yl- beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (4) and 3,4,6-tri-O-benzyl-beta-D-mannopyranose 3',4',6'-tri-O-acetyl-beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (14), respectively, containing an intramolecular NH-glycosidic linkage. The conventional deblocking of compounds 4 and 14 gave the completely deblocked trisaccharide 6-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-beta-D-mannopyranose beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (6) and the disaccharide beta-D-mannopyranose beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (16), respectively, containing an intact intramolecular NH-glycosidic bond. The unusual intra NH-glycosyl character makes the linkage rigid, and therefore these compounds should not only be useful for NMR studies but also as substrates or inhibitors of GlcNAc-transferases.
Synthetic monoterpene and aromatic beta-D-glucopyranosides, beta-rutinosides and 6-O-(alpha-L-arabinofuranosyl)-beta-D-glucopyranosides and their corresponding alcohols, diluted in a synthetic solution imitating wine, were isolated and separated by selective retention on Amberlite XAD-2. The corresponding recoveries and the conditions for the direct determination of these glycosides by gas chromatography and gas chromatography-mass spectrometry after derivatization were determined. Trifluoroacetylation gave the best results but trimethylsilylation provided complementary results. The separation of some diastereoisomeric monoterpene glycosides was also examined.