Glucose Hydroxyl Research Articles

Potent lipid peroxidation inhibitors from Withania somnifera fruits

A bioassay-guided purification of the methanolic extract of Withania somnifera fruits yielded novel withanamides A–I ( 1– 9 ) and withanolides ( 10– 13 ). Among the withanolides, compound 10 is novel. The structures of these compounds were determined by using FABMS, HRFABMS, 1D and 2D NMR spectral and chemical methods. The withanamides possess novel chemical structures and consisted of serotonin, glucose and long-chain hydroxyl fatty acid moieties. The stereochemistry of the hydroxyl group in the long-chain fatty acid moiety in compound 1 was determined by the modified Mosher's ester method. Compounds 1– 13 were tested for their ability to inhibit lipid peroxidation in a model system using large unilamellar vesicles. Withanamides 1– 5 and 9 inhibited lipid peroxidation by 98, 93, 79, 94, 81 and 86%, respectively, at 1 μg/mL. However, compounds 6– 8 inhibited the lipid peroxidation by 85, 82 and 90%, respectively, at 0.5 μg/mL. Withanolides 10– 13 were also tested and only compound 12 inhibited the lipid peroxidation by 82% at 10 μg/mL. To evaluate the structure activity relationships of withanamides A–I, compounds 14– 16 were purchased and their lipid peroxidation activity determined as in the case of compounds 1– 9 . Commercial antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), were also tested in this assay at 1 μg/mL and showed 80, 81 and 85% of inhibition, respectively. Our results suggest that the potent antioxidant activity exhibited by novel withanamides is probably due to the hydroxylated long-chain acyl group. This is the first report of withanamides, unique serotonin conjugates, from W. somnifera fruits.

Synthesis of the glycosidic precursor of isomeric marmelo lactones, volatile components of the quince fruit, Cydonia oblonga.

The glucosidic precursor of marmelo lactones was synthesized by employing a common intermediate which had been used for the synthesis of the glucosidic precursor of marmelo oxides. The synthesis was performed by modifying the former procedure. Monochloroacetyl was adopted to protect both the glucose and aglycon hydroxyl groups for selective transesterification in the presence of the glycosyl ester. Glycosylation of the aglycon carboxyl group with 1-alpha-bromopermonochloroacetylglucose and final selective alcoholysis yielded the target glucoside.

Synthesis of beta-D-glucosyl- and beta-D-fucosyl-glucoses using beta-glycosidase from Thermus thermophilus.

The thermostable beta-glycosidase from Thermus thermophilus, cloned and overexpressed in Escherichia coli was used to catalyze the transfer of beta-D-glucosyl and beta-D-fucosyl from the corresponding p-nitrophenyl-beta-D-glycopyranosides to a hydroxyl group of glucose in the synthesis of beta-D-glucosyl-D-glucopyranoses and beta-D-fucosyl-D-glucopyranoses. The yields in disaccharides produced under conditions of non-initial velocity were very attractive and the formation of the beta(1-3) linked disaccharides was largely favored. The enzyme could constitute a valuable biocatalyst for the synthesis of disaccharides involving such structures as, for example, Bifidus factors.

Higher iodinated analogues of d-glucose: syntheses of 3- C-iodomethyl, 6- C-iodomethyl and 6- C-iodophenyl derivatives

C-Substituted iodinated analogues of d-glucose have been prepared from diacetone- d-glucose or d-glucuronic acid derivatives; in these compounds, each hydroxyl group of glucose is present.

Enzymatic synthesis of unsaturated fatty acid glucoside esters for dermo-cosmetic applications.

Unsaturated fatty acid alpha-butylglucoside esters were prepared by enzymatic esterification of alpha-butylglucoside in nonaqueous media. Conditions were firstly optimized using oleic acid as acyl group. Synthesis was possible in several solvents but the presence of water co-product in the medium limited the reaction to a thermodynamic equilibrium corresponding to a maximal conversion yield of 62%. In pure molten substrates, the removal of water under reduced pressure enabled yields superior to 95% to be obtained. Product profiles depended on enzyme origin : whatever the support, immobilized lipase B from Candida antarctica proved to be far more regioselective for the primary hydroxyl group of glucose than immobilized lipase from Rhizomucor miehei. Results obtained could be easily transposed to the acylation of alpha-butylglucoside with a commercial mixture of unsaturated fatty acids containing more than 60% of linoleic acid. The biocatalyst could be recycled more than ten times without any significant activity loss.

A biochemical mechanism whereby Paecilomyces variotii can overcome the toxicity of the wood protectant borate

The tolerance of Paecilomyces variotii to borate used as a wood preservative was investigated. P. variotii was able to grow in the presence of up to 8 g l −1 borax in liquid malt extract cultures and on solid substrates such as malt–agar and borax-treated Scots pine, larch, and spruce sawdusts. The fungus excreted increased amounts of β- d-1,4-glucosidase when grown on borax-treated sawdust, a mechanism whereby increased amounts of glucose could be obtained for growth. Boron and glucose in the medium form a complex between the hydroxyl groups of glucose and boron, and supplying increased amounts of glucose in liquid culture enabled the fungus to grow in increasing concentrations of borax. A stable white mutant was selected from growth in high borate concentrations with similar characteristics to the parent with respect to β- d-1,4-glucosidase secretion, but with a changed morphology in that it did not release aerial spores. The mutant has potential uses in integrated-control treatments as wood protectants.

Ultraviolet spectra and structure of zinc-cellulose complexes in zinc chloride solution

The spectral characteristics of aqueous zinc chloride solutions (67% w/w) containing cellulose, cellobiose, maltose, β-methyl glucoside, and glucose were compared. The results suggest that zinc ion forms loose complexes with the C2 or C3 hydroxyl groups of glucose or methyl glucopyranoside. The absorption of light in the 200–220 nm range indicates the formation of these types of complexes. In solutions containing cellobiose or cellulose, zinc ion forms complexes with the hemiacetal oxygen atom of the anhydroglucose at the nonreducing end and a hydroxyl group of an anhydroglucose unit at the reducing end. This type of complex absorbs at 290 nm. Light absorption of cellobiose solutions at 235 nm was also correlated with similar complexes involving the anomeric oxygen at the reducing end of cellobiose. The absorption at 290 nm was proportional to the zinc chloride concentration. The presence of calcium ion also enhances the absorption; however, ion alone cannot form a complex with cellulose. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1441–1446, 1999

Comparative stereochemical analysis of glucose-binding proteins for rational design of glucose-specific agents

There is a need for synthesizing glucose-sensitive molecules which can be used in glucosesensors and self-regulating insulin delivery devices. Currently, glucose-sensitive proteins, such as glucoseoxidase and concanavalin A (Con-A), are used for detecting glucose molecules. For long-term in vivoapplications, it is necessary to synthesize non-proteineous glucose-sensitive molecules which are biocompatible,nontoxic, cost-effective, and independent of environmental factors such as pH, ionic strength, orthe presence of divalent cations. As a first step toward synthesizing glucose sensitive molecules, we have compared glucose-bindingsites of four different types of glucose-binding proteins. They are human β-cell glucokinase, D-xyloseisomerase, lectins (Lathyrus ochrus isolectin I and Con-A), and glucose/ galactose binding protein. Analysisof the glucose-binding sites of their 3-dimensional crystal structures showed that the hydrogen bondsbetween the hydroxyl groups of glucose and a few types of amino acid residues of proteins provided themain attraction. In some cases, the same atom was involved in multiple hydrogen bonds. Hydrophobicinteractions between the pyranose ring of glucose and aromatic rings of hydrophobic amino acid residuesalso played an important role in the glucose specificity. A sandwich geometry was observed among thehydrophobic groups. This comparative stereochemical analysis suggests that a possible glucose bindingsite can be made by placing Asp and Asn around glucose for hydrogen bonding and Phe on both sidesof glucose for hydrophobic interaction.

Structural analysis of UDP-sugar binding to UDP-galactose 4-epimerase from Escherichia coli.

UDP-galactose 4-epimerase from Escherichia coli catalyzes the interconversion of UDP-galactose and UDP-glucose through the transient reduction of the tightly bound cofactor NAD+. The enzyme is unique among the NAD+-dependent enzymes in that it promotes stereospecific reduction of the cofactor but nonstereospecific hydride return during normal catalysis. In addition to hydride transfer, the reaction mechanism of epimerase involves two key features: the abstraction of a proton from the 4'-hydroxyl group of glucose or galactose by an active site base and the rotation of a 4-ketopyranose intermediate in the active site pocket. To address the second issue of movement within the active site, the X-ray structures of reduced epimerase complexed with UDP-mannose, UDP-4-deoxy-4-fluoro-alpha-D-galactose, or UDP-4-deoxy-4-fluoro-alpha-D-glucose have been determined and refined to 1.65, 1.8, and 1.65 A resolution, respectively. A comparison of these models to that of the previously determined epimerase/NADH/UDP-glucose abortive complex reveals that the active site accommodates the various sugars by simple rearrangements of water molecules rather than by large changes in side chain conformations. In fact, the polypeptide chains for all of the epimerase/NADH/UDP-sugar complexes studied thus far are remarkably similar and can be superimposed with root-mean-square deviations of not greater than 0.24 A. The only significant differences between the various enzyme/UDP-sugar models occur in two of the dihedral angles defining the conformation of the UDP-sugar ligands.

Thermotropic Liquid Crystalline Glucose Derivatives with Mesogenic side Chains

Abstract Many glucose derivatives have been studied so far for their liquid crystalline behavior. Penta-O-n-alkanoylglucopyranoses have been reported to form discotic columnar mesophases. Thermotropic liquid crystals of glucose with mesogenic side chains, consisting of a mesogen, an alkyl spacer and a tail, form the subject of this study. The glucose derivatives were prepared by complete esterification of the hydroxyl groups of glucose with the mesogenic side chains. Their characterization was based on the analysis from cross polarizing microscopy, differential thermal calorimetery, wide-angle X-ray diffraction pattern and nuclear magnetic resonance (both 13C and 1H) spectra. Smectic and chiral nematic (cholesteric) phases have been observed in these macromolecules. The effect on the phase behavior of varying the tail length in the side chains of the molecule was studied. The structural arrangement of such molecules has been proposed based on the observations. These are reported here as the first such obs...

Glucose-Sensing Electrode Coated with Polymer Complex Gel Containing Phenylboronic Acid

We have prepared a copolymer containing both phenylboronic acid and tertiary amine moieties. The copolymer forms a stable complex with poly(vinyl alcohol) (PVA) since boronate moieties interact with PVA hydroxyl groups. The polymer-polymer complex changes its swelling degree with glucose concentration in Dulbecco's phosphate-buffered saline solution (PBS) at pH 7.4, due to the higher complex formation of boronic acid moieties with glucose hydroxyl groups over those in PVA. Glucose-responsive swelling changes of a membrane complex were then utilized to control glucose-responsive current changes with a membrane-coated platinum electrode. Glucose addition to PBS induces swelling of the cast gel membrane, leading to increased diffusion of ion species and thus increased measurable current changes. Since the addition of methyl α-d-glucoside has little influence on the current changes, the current change by the addition of glucose is indicative of the high selectivity of this system for glucose and its cis-hydroxyl groups in glucose. It is observed that current changes are proportional to glucose concentration in the range 0-300 mg/dL. This range corresponds well to physiological blood glucose levels. Current change rates determined from the slope of the time course immediately after glucose addition are also proportional to glucose concentration within this range, yielding even higher sensitivity to the change in glucose concentration. Reproducible signal output is also demonstrated by repetitive, stepwise glucose concentration changes. These results support the applicability of the platinum electrode coated with the gel membrane complex comprising a phenylboronic acid-containing polymer and PVA for a novel glucose-sensing device.

Site-directed mutagenesis studies on the determinants of sugar specificity and cooperative behavior of human beta-cell glucokinase.

The determinants of sugar specificity and cooperative behavior of human beta-cell glucokinase were studied by mutating several active site residues and performing a steady-state kinetic analysis of the purified mutant and wild-type enzymes after their expression in Escherichia coli. Asn-204, Glu-256, and Glu-290 were predicted from molecular modeling to interact with the 3-OH, 4-OH, 2-OH, and 1-OH groups of glucose. Mutation of these residues resulted in enzymes with decreased values of kcat and increased values of Km for glucose, mannose, and 2-deoxyglucose. Lys-56 is also predicted to make an interaction with the side chain of Glu-256 and its mutation increased the Km for glucose, deoxyglucose, mannose, and fructose by 4-, 4-, 3-, and 10-fold, respectively, and also increased the kcat for fructose by 5-fold. The Ki values for N-acetylglucosamine and mannoheptulose for the wild-type enzyme were 0.2 and 0.8 mM, respectively, and mutation of glucose binding residues to alanine resulted in an increase of about 3 orders of magnitude in these Ki values. Mutation of residues that directly hydrogen bond glucose hydroxyls (Asn-204, Glu-256, and Glu-290) to alanine resulted in enzymes that did not exhibit cooperative behavior, but mutation of Lys-56 or other residues that do not directly contact glucose had no effect on the Hill coefficient. Only glucose and deoxyglucose exhibited cooperative behavior. The results 1) confirm the predictions of the model that Asn-204, Glu-256, and Glu-290 are important residues involved in catalysis and hydrogen bonding glucose hydroxyl groups, 2) provide evidence for a role of Lys-56 in hexose binding, and 3) are consistent with the cooperative behavior of glucokinase being mediated by interactions of other regions of the protein with the highly conserved active site glucose binding residues.

UDP-rhamnose:flavanone-7-O-glucoside-2“-O-rhamnosyltransferase. Purification and characterization of an enzyme catalyzing the production of bitter compounds in citrus.

The rhamnosyltransferase catalyzing the production of the bitter flavanone-glucosides, naringin and neohesperidin, was purified to homogeneity. The enzyme catalyzes the transfer of rhamnose from UDP-rhamnose to the C-2 hydroxyl group of glucose attached via C-7-O- of naringenin or hesperetin. To our knowledge this is the first complete purification of a rhamnosyl-transferase. The enzyme from young pummelo leaves was purified greater than 2,700-fold to a specific activity of over 600 pmol/min/mg of protein by sequential column chromatographies on Sephacryl S-200, reactive green 19-agarose, and Mono-Q. The enzyme was selectively eluted from the green dye column with only three other proteins by a pulse of the substrate hesperetin-7-O-glucoside followed by UDP. The rhamnosyltransferase is monomeric (approximately 52 kDa) by gel filtration and electrophoresis. The enzyme rhamnosylates only with UDP-rhamnose. Flavonoid-7-O-glucosides are usable acceptors but 5-O-glucosides or aglycones are not. It is inhibited by 10 microM UDP, its end product, but not by naringin or neohesperidin. Several flavonoid-aglycones at 100 microM inhibited the rhamnosyltransferase; UDP-sugars did not. The Km for UDP-rhamnose was similar with prunin (1.3 microM) and hesperetin-7-O-glucoside (1.1 microM) as substrate. The affinity for the natural acceptor prunin (Km = 2.4 microM) was much higher than for hesperetin-7-O-glucoside (Km = 41.5 microM). The isolation of the gene may enable its use in genetic engineering directed to modifying grapefruit bitterness.

Multinuclear NMR studies of water in solutions of simple carbohydrates.

The dependence of water proton and deuterium transverse relaxation rates on pulse spacing is used to investigate the hydrogen exchange kinetics and water reorientational dynamics in glucose solutions over a wide concentration range. A complementary T 1ρ dispersion analysis is also undertaken. The results show that within the pH range 4–8 proton exchange between glucose and water occurs primarily by a non-ionic, cyclic transfer mechanism involving the interaction of two water molecules per glucose hydroxyl group. Interaction with the glucose introduces a slight anisotropy into the reorientational motion of the water. The two correlation times characterizing this anisotropic motion are estimated from the deuterium relaxation data. Similar phenomena are expected in all aqueous carbohydrate systems having accessible hydroxyl groups.

The molecular basis of the low hemolytic activity of C4 molecules from low-C4 mice with IgM-coated erythrocytes.

This study investigated the origin of the different hemolytic activity of two allotypes of murine C4, C4H (C4-high) and C4L (C4-low) in the presence of IgM-coated erythrocytes. C4H displayed a threefold higher hemolytic titer (expressed in hemolytic units/microgram protein) than C4L. No difference was found between c4H and C4L either in stability at 37 degrees C at different pH values and in the rate of C4H and C4L hydrolysis by activated Cl. The major functional difference was found in the covalent binding capacity to IgM-coated erythrocytes, with the amount of C4H bound being about threefold higher than that of C4L. A marked difference in the reactivity of the C4b fragment of C4H and C4L toward amino and hydroxyl groups was detected. Using glycine and glucose to competitively inhibit the binding of C4H and C4L, it was observed that C4L selects preferentially for the amino groups of glycine, whereas C4H reacted preferentially with the hydroxyl groups of glucose. Furthermore, the chemical modification of the red cells amino groups by ethylacetimidate, had no appreciable effect on the binding of C4H, but reduced that of C4L. Southern blot hybridization experiments using Hind III-digested liver DNA and a cDNA probe derived from the 5' end of the mRNA (clone pAT-A) indicated that the C4H allele was associated with a 5-kb Hind III fragment, whereas the C4L allele was associated with a 15-kb Hind III fragment. The possibility that a structural difference between C4H and C4L is responsible for their different reactivities is discussed.

Synthesis of phosphatidyl-β-glucosyl glycerol containing a dioleoyl diglyceride moiety : Application of the tetraisopropyldisiloxane-1,3-diyl (tips) protecting group in sugar chemistry. part IV

The preparation of phosphatidyl-β-glucosyl diglyceride 12c is described. The synthesis of glycophospholipid 12c was accomplished by using: (a) the levulinoyl group for the temporary protection of the glucose hydroxyl functions of 6b , which could then be converted into the dioleoyl substituted derivative 7c ; (b) the tetraisopropyldisiloxane-1,3-diyl (TIPS) group to protect the 3'- and 4'-hydroxyl groups of 7c , in a two step procedure, to afford compound 8 ; (c) a 2,4-dichlorophenyl protected phosphatidic acid derivative 11 . Compound 11 could be selectively coupled to the primary hydroxyl function of 8 to afford the fully protected glycophospholipid 12a . Finally, removal of the 2,4-dichlorophenyl and TIPS protecting groups from 12a was performed with syn-4-nitrobenzaldoximate and fluoride ions, respectively, to afford glycophospholipid 12c .

Physical studies of cell surface and cell membrane structure. Deuterium nuclear magnetic resonance studies of N-palmitoylglucosylceramide (cerebroside) head group structure.

Deuterium Fourier-transform nuclear magnetic resonance spectra of N-palmitoyl[2,3,4,6,6-2H5]glucosylceramide, N-palmitoyl[1-2H]glucosylceramide, N-palmitoyl-[5,6,6-2H3]glucosylceramide, and N-palmitoyl[6,6-2H2]-glucosylceramide have been obtained at 55.3 MHz (corresponding to a magnetic field strength of 8.5 T) for lipids as multilamellar dispersions in excess water at 90 degrees C, above the gel to liquid-crystal phase transition temperature (Tc = 82 degrees C). Spectra were also obtained for these same lipids dispersed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, and cholesterol, all in excess water at 90 degrees C. The results are analyzed in terms of a model in which the lipid undergoes fast axial diffusion, together with a "wobbling" of the polar head group, by mathematical methods similar to those used previously for the choline and ethanolamine head groups in phosphatidylcholines and phosphatidylethanolamines [Skarjune, R., & Oldfield, E. (1979) Biochemistry 18, 5903--5909]. However, contrary to the results obtained in the previous study, which indicated many possible conformations for the choline and ethanolamine head groups, results with labeled cerebrosides yield at most a few orientations for the glucose head group in each of the systems studied. Furthermore, where multiple solutions do occur, they fall within a narrow orientational subspace so that all solutions exhibit the same general features. We also show that the order parameter describing the head group wobble is fully determined for each system, and it indicates a rather mobile structure for the cerebroside head group, in a variety of environments. In each system studied the polar head group projects essentially straight up from the bilayer surface into the aqueous region, thereby permitting maximum hydration of the four glucose hydroxyl groups by bulk water molecules.

Glucose Induced H+Influx and Transient Currents in Excised Roots: particularly those ofZea mays

The application of D-glucose to solutions bathing excised maize, wheat, pea and bean roots causes a rapid depolarization of the electrical potentials between the cut tops of the roots and the bathing solutions. Similar effects are observed for the plasma membrane potentials of maize lateral roots. A flow cell apparatus was used to demonstrate qualitative and quantitative relations between glucose induced H+ influx and the transient decrease in current through the root. The current changes appear to be due entirely to H+ fluxes. Current and H+ fluxes are strongly influenced by external pH, the optimum pH for glucose induced current change being about 4.0. A similar pH optimum was found for 3-O-methyl-D-glucopyranoside but 1-O-methyl-α-D-glucopyranoside did not significantly affect the trans-root potential at any pH, suggesting a significant role for the anomeric hydroxyl group of glucose. Compounds which depolarize the trans-root potential also inhibit the glucose induced depolarization. Surface -SH groups are probably not involved in the glucose/H+ cotransport. Eadie-Hofstee plots relating the depolarization of trans-root potential to the concentrations of D-glucose or 3-O-methyl-D-glucopyranoside have shown that Km values increase with increasing monosaccharide concentration and are very similar to reported values of 3-O-methyl-D-glucopyranoside uptake in maize root segments. Km values for a similar range of D-glucose concentrations do not vary significantly with pH or with membrane depolarization due to a 10-fold increase of KCl concentration. However, δVmax is lowered by an increase in external pH or a decrease in trans-root potential. It appears that both proton and electrical gradients can affect glucose induced H+ influx. The auxin herbicide, 2, 4-dichlorophenoxyethanoic acid (0.01 mM) stimulates the glucose induced depolarizations in a manner consistent with an increase in cytoplasmic pH. This is discussed in relation to the reported action of indole-3-acetic acid and fusicoccin on maize root tissue.

Alcoxymethyl Ethers of Glucose and Its Oligomers Part II. Composition and Structure of Alcoxymethyl Glucose Ethers

AbstractDodecoxymethyl glucose ethers were separated by TLC and column chromatography and the main components were identified. The fraction of monododecoxymethyl glucose ethers was separated into positional isomers. The reactivity of hydroxyl groups of glucose in the reaction with dodecoxymethyl chloride was investigated.

Electrophoresis of algal glucans

The ability of reactive dyes based on chloro-s-triazine to react with the primary and secondary hydroxyl groups of glucose, forming covalent bonds, has been used to dye the storage polyglucosides of the algae, Cytmidium caldarium, Oscillatoria princeps, Rhodymenia pertusa and Spirogyra setiformis, prior to electrophoresis on cellulose polyacetate strips in borate buffer. The technique resolves mixtures of glucans and defines some of the parameters of the internal structure of these glucans. The similarity of the glucans from Cyanidium caldarium and Oscillatoria princeps is evident using this method. The two components of the “starch” from Spirogyra setiformis have been studied and identified by their reactions with the dye and the mobilities of the dyed components during electrophoresis. Inferences as to the biphyletic evolutionary pathways leading from the Cyanophyceae to the Rhodophyceae and the Chlorophyceae can be made based on the data.