Calorimetric studies on hydrolysis of glucosides. 3. Heats of hydrolysis of alpha-1,4 glucosidic linkages involved in higer glucosides.
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Guaiacol (2-methoxyphenol) and curcumin [1E,6E-1,7-di(4-hydroxy-3-methoxy-phenyl)-1,6-heptadiene-3,5-dione] were converted into their corresponding glucosides using glucose and an amyloglucosidase from Rhizopus. Guaiacol-alpha-D: -glucoside yields ranged from 3 to 52% with the highest at pH 7.0. Curcumin-bis-alpha-D: -glucoside yields ranged from 3 to 48% with the highest at pH 4.0 with 50% (w/w D: -glucose) of enzyme. The phenolic hydroxyl group of guaiacol and both phenolic hydroxyl groups of curcumin were glucosylated at the C1 carbon of alpha-D: -glucose indicating that the enzymatic reaction is stereospecific. Both guaiacol-alpha-D: -glucoside and curcumin-bis-alpha-D: -glucosides had antioxidant activities.
Zygaena larvae sequester the cyanogenic glucosides linamarin and lotaustralin from their food plants (Fabaceae) as well as carry out de novo biosynthesis of these compounds. In this study, Zygaena filipendulae were reared on wild-type Lotus corniculatus and wild-type and transgenic L. japonicus plants with differing content and ratios of the cyanogenic glucosides linamarin and lotaustralin and of the cyanoalkenyl glucosides rhodiocyanoside A and D. LC-MS analyses, free choice feeding experiments and developmental studies were used to examine the effect of varying content and ratios of these secondary metabolites on the feeding preferences, growth and development of Z. filipendulae. Larvae reared on cyanogenic L. corniculatus developed faster compared to larvae reared on L. japonicus although free choice feeding trials demonstrated that the latter plant source was the preferred food plant. Larvae reared on acyanogenic L. corniculatus showed decelerated development. Analysis of different life stages and tissues demonstrate that Z. filipendulae strive to maintain certain threshold content and ratios of cyanogenic glucosides regardless of the composition of the food plants. Despite this, the ratios of cyanogenic glucosides in Z. filipendulae remain partly affected by the ratio of the food plant due to the high proportion of sequestering that takes place.
Six new sulfur-containing bis-iridoid glucosides, saprosmosides A-F (1-6), were isolated from the leaves of Saprosma scortechinii. From the stems of this same plant, two new iridoid glucosides, 3,4-dihydro-3-methoxypaederoside (8) and 10-O-benzoyldeacetylasperulosidic acid (12), were isolated. Their structures were elucidated by means of chemical, NMR, and mass spectroscopic methods. Additionally, 11 known iridoid glucosides were isolated and characterized as deacetylasperuloside, asperuloside, paederoside (7), deacetylasperulosidic acid (9), scandoside, asperulosidic acid, 10-acetylscandoside, paederosidic acid (10), 6-epi-paederosidic acid (11), methylpaederosidate, and monotropein. The structures of the new bis-iridoid glucosides were formed by intermolecular esterification between the glucose and carboxyl groups of three monomeric iridoid glucosides (7, 9, and 10).
ATP-dependent beta-glucoside kinase (BglK) has been purified from cellobiose-grown cells of Klebsiella pneumoniae. In solution, the enzyme (EC ) exists as a homotetramer composed of non-covalently linked subunits of M(r) approximately 33,000. Determination of the first 28 residues from the N terminus of the protein allowed the identification and cloning of bglK from genomic DNA of K. pneumoniae. The open reading frame (ORF) of bglK encodes a 297-residue polypeptide of calculated M(r) 32,697. A motif of 7 amino acids (AFD(7)IG(9)GT) near the N terminus may comprise the ATP-binding site, and residue changes D7G and G9A yielded catalytically inactive proteins. BglK was progressively inactivated (t(12) approximately 19 min) by N-ethylmaleimide, but ATP afforded considerable protection against the inhibitor. By the presence of a centrally located signature sequence, BglK can be assigned to the ROK (Repressor, ORF, Kinase) family of proteins. Preparation of (His6)BglK by nickel-nitrilotriacetic acid-agarose chromatography provided high purity enzyme in quantity sufficient for the preparative synthesis (200-500 mg) of ten 6-phospho-beta-d-glucosides, including cellobiose-6'-P, gentiobiose-6'-P, cellobiitol-6-P, salicin-6-P, and arbutin-6-P. These (and other) derivatives are substrates for phospho-beta-glucosidase(s) belonging to Families 1 and 4 of the glycosylhydrolase superfamily. The structures, physicochemical properties, and phosphorylation site(s) of the 6-phospho-beta-d-glucosides have been determined by fast atom bombardment-negative ion spectrometry, thin-layer chromatography, and (1)H and (13)C NMR spectroscopy. The recently sequenced genomes of two Listeria species, L. monocytogenes EGD-e and L. innocua CLIP 11262, contain homologous genes (lmo2764 and lin2907, respectively) that encode a 294-residue polypeptide (M(r) approximately 32,200) that exhibits approximately 58% amino acid identity with BglK. The protein encoded by the two genes exhibits beta-glucoside kinase activity and cross-reacts with polyclonal antibody to (His6)BglK from K. pneumoniae. The location of lmo2764 and lin2907 within a beta-glucoside (cellobiose):phosphotransferase system operon, may presage both enzymatic (kinase) and regulatory functions for the BglK homolog in Listeria species.
A particulate enzyme fraction from Mycobacterim smegmatis catalyzed the transfer of -14C-glucose from the UDP--14C-glucose into neutral glycolipids. The two major radioactive components were purified by column chromatography on O-diethylamino ethyl cellulose (acetate) and thin layer chromatography on silica gel in several solvents. The first product yielded a water-soluble component upon saponification, which had a hexoseglycerol ratio of 1:1 with all of the hexose being identified as glucose. The second product yielded a water-soluble component upon saponification which contained hexose and glycerol in a 2:1 ratio and, in addition to glucose, contained lesser amounts of mannose and galactose. Palmitate and oleate were the predominant fatty acids and were present in equimolar amounts. The products thus have been identified as monoglycosyldiglyceride and diglycosyldiglyceride. The diglycosyldiglyceride could also be labeled with -14C-galactose when UDP--14C-galactose served as the donor, but the monoglycosyldiglyceride was only slightly labeled with -14C-galactose. Membrane fractions from mung bean seedlings catalyzed the transfer of -14C-glucose from UDP--14C-glucose into a neutral glycolipid which has been purified by thin layer chromatography and analyzed by combined gas liquid chromatography-mass spectrometry. It was determined to be a steryl glucoside with the two major sterol components being betasitosterol and stigmasterol linked to beta-D-glucose. Particulate fractions from developing cotton fibers also catalyzed the formation of steryl glucosides and, in addition, they catalyzed the esterification of steryl glucosides at the 6 position of glucose with fatty acids (primarily palmitate and oleate) from an andogenous acyl donor. Both the glucosyl transferase and the acyltransferase have been solubilized with Triton X-100 and partially purified by chromatography on Sephadex G-200. The acyltransferase activity was reconstituted by the addition of the steryl glucoside and a phospholipid acyl donor.
The synthesis is described of highly acid-sensitive, 1,1-dialkyl-1-methoxymethyl glucosides (acetal-glucosides) as potential anti-cancer prodrugs. Reaction of 2,3,4,6-tetra-O-acetyl-1-O-trimethylsilyl-beta-D-glucopyranose (4) severally with various aliphatic and alicyclic ketones and methyl trimethylsilyl ether, in the presence of catalytic amounts of trimethylsilyl trifluoromethanesulfonate, afforded the corresponding acetylated acetal-beta-glucosides, e.g., acetone gave 1-methoxy-1-methylethyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside (7a). Likewise the alpha-anomer (8a) of 7a was obtained from the alpha-anomer of 4. Deacetylation of the tetra-acetates then gave the acetal-alpha- and -beta-glucosides.
A total of 33 iridoid and secoiridoid glucosides were detected by gas chromatography on several columns such as OV-1 or OV-17. Representative glucosides were then subjected to gas chromatography-mass spectrometry, giving some characteristic peaks that permitted the discrimination of both types of glucosides from other compounds in most instances. The successful detection of both types of glucosides in several plant extracts showed the applicability of this combination of methods to small amounts of plant materials.
Malvidin-3-glucoside has been labeled by enzymatic synthesis in a single-step experiment. Catechol-O-methyl transferase catalyzed the B-ring methylation of petunidin-3-glucoside, and S-Adenosyl-L-[methyl-(3)H] methionine was the methyl donor. Solid phase extraction and preparative high-performance liquid chromatography were necessary to separate [3'-O-methyl-(3)H]malvidin-3-glucoside from an isomer and the starting material. The specific activity was 2.2 Ci mmol(-1), and the yield of incorporation was 1.1%. A possible application of the labeled material is the study of anthocyanin reactions in complex mixtures such as red wine where products are difficult to isolate and analyze.
Fractionation of ethyl acetate extract of Lavandula stoechas aerial parts revealed the presence of a novel acetylated glucoside (1) together with apigenin 7-O-glucoside (2) and luteolin 7-O-glucoside (3). The structures of these compounds were elucidated by spectroscopic analyses, notably UV, MS, and NMR.
Quercetin is a typical antioxidative flavonoid found in vegetables, which is more commonly present as its glucosides, quercetin-3-glucoside (Q3G) and quercetin-4'-glucoside (Q4'G). The main aim of this study was to estimate the antioxidant activity of Q3G and Q4'G on iron ion-driven lipid peroxidation of the gastrointestinal mucosa. Q4'G markedly suppressed the lipid peroxidation when rat gastrointestinal mucosa homogenates were incubated with Fe(NO3)3 and ascorbic acid. Its effectiveness was greater as compared to that of Q3G and comparable to that of quercetin aglycone. Furthermore, Q4'G yielded higher amounts of quercetin aglycone than Q3G on incubation with the homogenates. However, Q4'G showed a lower chelating activity in comparison to Q3G. These results indicate that Q4'G, even though it has a low chelating activity, because of its efficient conversion to antioxidative aglycone on exposure to the mucosa, can act as a powerful antioxidant on iron ion driven lipid peroxidation in the intestinal mucosa. Thus, vegetables rich in Q4'G, such as onion, are likely to serve as favorable antioxidant sources for suppressing iron-induced oxidative stress in the intestinal tract.
New antiallergic and antimicrobial dihydroisocoumarins, thunberginols C, D, and E, were isolated from Hydrangeae Dulcis Folium, the fermented and dried leaves of Hydrangea macrophylla SERINGE var. thunbergii MAKINO, together with new dihydroisocoumarin glycosides, thunberginol G 3'-O-glucoside and (-)-hydrangenol 4'-O-glucoside. Their chemical structures have been determined on the basis of chemical and physicochemical evidence. Thunberginols C, D, E, G, and (-)-hydrangenol 4'-O-glucoside showed antiallergic activity in the in vitro bioassay using the Schults-Dale reaction in sensitized guinea pig bronchial muscle, and they also exhibited antimicrobial activity against oral bacteria.
Two new triterpenol glycosides were isolated from the rhizomes of Cimicifuga dahurica (Ranunculaceae): 3-arabinosyl-24-O-acetylhydroshengmanol 15-glucoside (1), C43H70O16, mp 222-223 degrees C, [alpha]D +21.0 degrees and 3-xylosyl-24-O-acetylhydroshengmanol 15-glucoside (2), C43H70O16, mp 208-210 degrees C, [alpha]D +9.5 degrees. On acidic hydrolysis, 1 afforded cimigenol (3) as an aglycone, and glucose and arabinose as sugars. On enzymatic hydrolysis with molsin, 1 afforded 24-O-acetylhydroshengmanol 15-O-glucoside (4). On the basis of chemical and spectral data, the structure of 1 was proposed to be (23R,24S)-24-acetoxy-3-O-alpha-L-arabinopyranosyloxy-16,23-e poxy-9,19- 15-O-beta-D-glucopyranoside. The other glycoside (2) showed, in its 13C-NMR spectrum, a pattern of chemical shifts very similar to that of 1. On acidic hydrolysis, 2 afforded cimigenol (3), xylose and glucose. On enzymatic hydrolysis with molsin, 2 afforded 4. From these results, the structure of 2 was proposed to be (23R,24S)-24-acetoxy-3-O-beta-D-xylopyranosyloxy-16,23-epoxy -9,19-cyclolanostane-15 alpha,16 xi,25-triol 15-O-beta-D-glucopyranoside.
From the leaves of Alangium kurzii, a new tetrahydroisoquinoline-monoterpene glucoside, 6-O-methyl-N-deacetylipecosidic acid and a new iridoid glucoside, 10-O-benzoyladoxosidic acid, were isolated along with alangiside, demethylalangiside, 6''-O-beta-D-glucosylhenryoside, uridine and four known flavonoid glycosides. The structures of new glucosides were determined on the basis of spectroscopic and chemical methods.
Mass spectrometric methodology based on the combined use of positive and negative electrospray ionization, collision-induced dissociation (CID) and tandem mass spectrometry (MS/MS) has been applied to the structural characterization of 6-hydroxyluteolin 7-O-glucoside and 7-O-glucosyl-(1 --> 3)-glucoside. In-source fragmentation of both glycosides at an increased potential yielded the protonated and deprotonated aglycone, allowing CID spectra to be obtained. The differentiation between quercetin and 6-hydroxyluteolin aglycones was achieved by product ion analysis of the protonated and deprotonated aglycone (m/z 303 and 301), that showed the characteristic product ions (1,3)A at m/z 151 and 153 for quercetin, and m/z 167 and 169 for 6-hydroxyluteolin, consistent with the trihydroxylated A-ring skeleton. In the negative ion mode both glycosides were shown to undergo collision-induced homolytic and heterolytic cleavages of the O-glycosidic bond producing the aglycone radical-anion [Y0-H]-* and Y0(-) product ions. At lower collision energy, various fragmentations involving the glucose moieties were observed with a relatively higher abundance for the monoglucoside compared to the diglucoside. In the latter case both the inner and the terminal glucose residues were involved in the fragmentations, giving useful information on the 1 --> 3 interglycosidic linkage. CID MS/MS analysis of the sodiated molecules gave complementary information for the structural characterization of the studied compounds. Fragmentation mechanisms are proposed for the observed product ions.
From the polar portion of the methanolic extract of the fruit of anise (Pimpinella anisum L.), which has been used as a spice and medicine since antiquity, four aromatic compound glucosides, an alkyl glucoside and a glucide were isolated together with 24 known compounds. The structures of the new compounds were clarified as (E)-3-hydroxyanethole beta-D-glucopyranoside, (E)-1'-(2-hydroxy-5-methoxyphenyl)propane beta-D-glucopyranoside, 3-hydroxyestragole beta-D-glucopyranoside, methyl syringate 4-O-beta-D-glucopyranoside, hexane-1,5-diol 1-O-beta-D-glucopyranoside and 1-deoxy-L-erythritol 3-O-beta-D-glucopyranoside by spectral investigation.
From the fruits of Sambucus canadensis four anthocyanin glycosides have been isolated by successive application of an ion-exchange resin, droplet-counter chromatography and gel filtration. The structure of the novel, major (69.8%) pigment, cyanidin 3-O-[6-O-(E-p-coumaroyl-2-O-(beta-D-xylopyranosyl)-beta-D- glucopyranoside]-5-O-beta-D-glucopyranoside, was determined by means of chemical degradation, chromatography and spectroscopy, especially homo- and heteronuclear two-dimensional NMR techniques. The other anthocyanins were identified as cyanidin 3-sambubioside-5-glucoside (22.7%), cyanidin 3-sambubioside (2.3%) and cyanidin 3-glucoside (2.1%).
Short-chained sugar compounds, thought to be involved in the synthesis of callose, were formed in small amounts from UDP-glucose by soluble extracts from hypocotyls of seedlings of Phaseolus aureus. The properties of the glycosides were investigated by treatment with various chemicals and analysis by paper chromatography, g.l.c. and mass spectrometry. The data obtained support the characterization of these compounds as myoinositol-beta-glucoside and diglucosylmyoinositol. The cyclitol moiety was provided by the enzyme extract. Free myoinositol was not the immediate substrate but a compound containing myoinositol, isolated from the enzyme extract, may be involved. The method of synthesis of these glucosides is compared with that of other cyclitol glycosides.