Glucopyranosyl Units Research Articles

Regioselective Esterification of Cardiac Glycosides Catalyzed by Novozym 435 and Lipase PS in Organic Solvents

The enzymatic acetylation in the organic solvents of a number of the important bioactive cardiac glycosides was investigated. With the bufanolide proscillaridin A and the cardenolide lanatoside C, acylation, as expected, occurred at the secondary 4′-OH of the rhamnopyranosyl unit of the former (by the action of Novozym 435 lipase) and the primary 6′′′′-OH of the terminal glucopyranosyl unit of the latter (best results obtained by the action of the lipase PS). Only lipase PS was found to be able to acylate the cardenolides digitoxin and digoxin at the 4‴-OH of their terminal digitoxose unit. The corresponding monoacetyl derivatives, both of which are commercialized drugs, could be isolated with good yields. The investigation of the Novozym 435-catalyzed acetylation of free D-digitoxose provided a possible explanation for the inability of this lipase to acylate digitoxin and digoxin.

Arbutin derivatives from the buds of Vaccinium dunalianum and their MS/MS spectrometric fragmentations

Four arbutin derivatives were isolated from the buds of Vaccinium dunalianum in which 4-hydroxyphenyl-6′-(3''- O - β - D -glucopyranosyl-4''-hydroxycinnamoyl)- O - β - D -glucopyranoside (1) was a new compound. The structure of the new compound was determined on the basis of NMR and HR-ESI-MS data. All the arbutin derivatives were subjected to the MS/MS analyses from which the MS/MS spectrometric fragmentations were summarized. • Four arbutin derivatives were obtained from the buds of Vaccinium dunalianum. • A new compound was identified. • The losses of glucopyranosyl and 4-hydroxyphenyl units were the main MS/MS elimination modes.

Modification of eggshell membrane to impart biospecific properties

AbstractEggshell membrane (ESM) represents an inexpensive, environmentally friendly and nontoxic byproduct. Besides the unique mechanical properties of the material, the ESM surface is rich in functional groups susceptible to further modifications. In the current study two modification pathways were applied to enrich the ESM surface with glucopyranosyl units. One was based on the reaction of activated surface carboxylic groups with glucosamine and the other exploited the reactivity of the surface amino groups for grafting poly(ethylene glycol) (PEG) chains bearing end glucopyranosyl and benzaldehyde moieties. The functionalization of the PEG chains with molar masses 400 and 1500 g mol−1 was evidenced from 1H NMR and 13C NMR spectral data. The modified ESMs were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The Brunauer–Emmett–Teller specific surface area and the total pore volume of ESM decreased upon modification. Decoration of ESM with glucopyranosyl units imparted protein recognition properties that were tested via binding studies with concanavalin A as model lectin. Further, grafting of glucose units via PEG linkers reduced bacterial adhesion onto the membrane surface. © 2021 Society of Industrial Chemistry.

CD Oxyanions as a Tool for Synthesis of Highly Anionic Cyclodextrin Polymers.

Water soluble highly anionic β-cyclodextrin-based polymers were synthesized by reaction between cyclodextrin oxyanion and pyromellitic anhydride. The synthesis method utilizes activation hydroxyl groups in anhydrous glucopyranosyl units (AGU) in the DMF solution with the use of NaH. In these conditions, like in the case of the cyclodextrin reactions in the highly alkaline media, there is a nucleophilic substitution of difunctional compounds, which develops a polymer network with various cyclodextrin substitution. Different molar ratios of the reagents were investigated in terms of molecular size, chemical structure and water solubility of the polymers. The separation of the polymer due to particle size by ultrafiltration process and HPSEC-MALLS-RI and MALDI-TOF MS measurements for molecular mass analysis were employed. The IR, H NMR, SEM, DSC and TG measurements were taken for the structural characterization of the polymers. Additionally, the solubility test and metal ion complexation processes were also investigated in a wide range of pH. These polymers could be used in several areas such as: improving the aqueous solubility of poor water-soluble molecules, removing heavy metals from waste water, protecting degradable substances or synthesizing new drug delivery systems.

Structure-Functional Activity Relationship of β-Glucans From the Perspective of Immunomodulation: A Mini-Review.

β-Glucans are a heterogeneous group of glucose polymers with a common structure comprising a main chain of β-(1,3) and/or β-(1,4)-glucopyranosyl units, along with side chains with various branches and lengths. β-Glucans initiate immune responses via immune cells, which become activated by the binding of the polymer to specific receptors. However, β-glucans from different sources also differ in their structure, conformation, physical properties, binding affinity to receptors, and thus biological functions. The mechanisms behind this are not fully understood. This mini-review provides a comprehensive and up-to-date commentary on the relationship between β-glucans' structure and function in relation to their use for immunomodulation.

Synthesis, Characterization and Evaluation of Cadmium Sulfide Nanoparticles Capped with Dextrin and Functionalized with Temozolomide

Nanoparticles are currently used as drug carriers. Temozolomide is an antineoplastic drug for tumor in central nervous system. It presents a half‐life of 1.8 hours. For this reason, requires high doses that are limited by side effects. Studies about the use of nanoparticles as drugs transporters have reported an increase the drug solubility, increase in half‐life and sustained release of the drug because it is protected from degradation and loss of therapeutic effect. This group has development and studied CdS nanoparticles capped with polymers and have showed being biocompatible and effective as drug carriers. To synthesize and characterize cadmium sulfide nanoparticles capped with dextrin functionalized with temozolomide and observe cell uptake. By means of the chemical method, the precursors were allowed to react to obtain the synthesis of CdS/dextrin nanoparticles. Subsequently, the nanoparticles were functionalized with temozolomide through a chemical method in which the OH groups of the dextrin were bounded to the NH2 Through the technique of Fourier‐transform infrared, the characteristic bonds were observed: at 840 cm−1 the α‐D glucopyranose bond, at 927 cm−1 the α(1–4) bonds; 1159 cm−1 glucopyranosyl units and at 1079 cm−1 the C‐O‐C, at 1025 cm−1 the C‐O bond, at 3399 cm−1 the OH group characteristic of dextrin. At 2001 cm−1 the C=N=N of diazomethane was found which is a toxic compound resulting from the formation of nanoparticles. Also at 3400 cm−1 there is the link N=H and 1610 cm−1 C = C or C = N of the temozolomide. According to the X‐ray results, the widening of 3 peaks corresponding to the crystalline planes characteristic of the cubic phase of the CdS is observed which are: (111), (220) and (311). Using the Scherrer formula d = 0.8λ/βcos θ was calculated that the average size of the nanoparticles is 3 nm. Due to the size of the semiconductor nanoparticles of CdS‐dextrin, they emit green fluorescence characteristic. Therefore, tumor cells treated with nanoparticles functionalized with temozolomide in epifluorescence microscope were observed and it was observed that the nanoparticles reached the cytoplasm and core of cells and produces the effect of temozolomide arresting cell cycle in phase G2 + M. The synthesis and characterization of CdS/dextrin nanoparticles functionalized with temozolomide resulted in 5nm, which are uptake by the cells and are distributed on the cytoplasm and core exerting the effect of the drug. The CdS/dextrin has the potential for being used as drug carriers and facilitating the pharmacological because cells up take them.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Synthesis and Unprecedented Complexation Properties of β-Cyclodextrin-Based Ligand for Lanthanide Ions.

Here, we report the synthesis and detailed studies on the coordination chemistry of a novel chemically modified polyaminocarboxylate (5) based on β-cyclodextrin (CD) scaffold for lanthanides. The target ligand is prepared in a highly efficient manner (seven total steps) from β-CD using the readily available iminodiacetic acid as a starting material. A propargyl group is attached to the iminodiacetate via N-alkylation, and the obtained derivative is efficiently conjugated to the β-CD scaffold via the copper(I)-mediated 1,3-dipolar cycloaddition. The generated 1,2,3-triazolmethyl residues advantageously provide a competent chelating group while displacing the metal coordination center away from the primary rim of β-CD, to afford the required conformational flexibility. The functional groups from each of the two adjacent glucopyranosyl units of β-CD complete a uniquely created octavalent coordination sphere for lanthanides while still sparing one site for dynamic water coordination. To help study the coordination chemistry of CD ligand 5, we also design a relevant maltoside ligand 6, which faithfully represents one submetal-binding section of ligand 5. Thanks to HRMS and NMR studies, we successfully elucidate the coordination chemistries of synthesized ligands. The octavalent coordination sphere of ligand 5 shows strong binding affinity to lanthanides. By potentiometric titration experiments, ligand 5 is found to bind gadolinium(III), forming 1:1, 1:2, and 1:3 multinuclear complexes with lanthanides, thus possessing great capacity for catalyzing the dynamic water-exchange. Further NMR studies also reveal that the formed ligand 5/Gd(III) complexes show significantly better abilities to alter T1 relaxivities of coordinated water than DOTA-Gd(III) and also some of the synthetic CD probes reported in the literature.

Preparation of a Salecan/poly(2-acrylamido-2-methylpropanosulfonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride) Semi-IPN Hydrogel for Drug Delivery.

Salecan is a water-soluble bacterial polysaccharide consisting of glucopyranosyl units linked by α-1,3 and β-1,3 glycosidic bonds. salecan is suitable for the development of hydrogels for biomedical applications, given its outstanding physicochemical and biological profiles. In this study we designed a new semi-interpenetrating polymer network hydrogel that introduces the salecan polysaccharide into a stimuli-responsive poly(2-acrylamido-2-methylpropanosulfonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride) (PAM) hydrogel matrix for controlled insulin release. We found that salecan not only tunes the structure and pore size of the PAM hydrogels, but also endows them with adjustable water release rates. More importantly, in vitro drug loading/release assays demonstrated that insulin is efficiently loaded into the resulting hydrogels and can be released in an on-demand manner by controlling the pH and salecan dose. Furthermore, cell viability and cell adhesion experiments verified the cell compatibility of these hydrogel carriers. Together, these results make salecan-incorporated PAM hydrogels promising materials for drug delivery.

Fabrication and Characterization of a Novel Anticancer Drug Delivery System: Salecan/Poly(methacrylic acid) Semi-interpenetrating Polymer Network Hydrogel.

Salecan is a novel linear extracellular polysaccharide with a linear backbone of 1-3-linked glucopyranosyl units. Salecan is suitable for preparing hydrogels for biomedical applications due to its prominent physicochemical and biological profiles. In this contribution, a variety of innovative semi-interpenetrating polymer network (semi-IPN) hydrogels consisting of Salecan and poly(methacrylic acid) (PMAA) were developed via free radical polymerization for controlled drug delivery. The successful fabrication of the semi-IPNs was verified by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric (TGA) measurements. Scanning electron microscopy (SEM) and rheology analyses demonstrated that the morphological and mechanical behaviors of the resultant hydrogels were strongly affected by the contents of Salecan and cross-linker N,N'-methylenebis(acrylamide) (BIS). Moreover, the swelling properties of these hydrogels were systematically investigated, and the results indicated that they exhibited pH sensitivity. The drug delivery applications of such fabricated hydrogels were further evaluated from which doxorubicin (Dox) was chosen as a model drug for in vitro release and cell viability studies. It was found that the Dox release from the Dox-loaded hydrogels was significantly accelerated when the pH of the release media decreased from 7.4 to 5.0. Toxicity assays confirmed that the blank hydrogels had negligible toxicity to normal cells, whereas the Dox-loaded hydrogels remained high in cytotoxicity for A549 and HepG2 cancer cells. All of these attributes implied that the new proposed semi-IPNs serve as potential drug delivery platforms for cancer therapy.

NMR characterization of chemically synthesized branched α-dextrin model compounds

1H and 13C NMR chemical shifts were accurately determined by consistent referencing for an extensive set of chemically synthesized branched α-glucan model compounds. The model compounds include anomerically fixed and reducing oligosaccharides ranging in size from isomaltose to a doubly branched decasaccharide. Both the 13C1 chemical shift and the 13C6 chemical shifts in α-(1→6) glycosidic bonds are strongly dependent on the chemical structure in the vicinity of the branch point, especially on the addition of glucopyranosyl units towards the non-reducing end of the backbone chain. The conformational sampling at the branch point of the branched α-glucan model compounds was experimentally probed with homo-nuclear scalar couplings. Substitution at O6 consistently increases the fraction of C6–O6 trans conformations, but to a lesser extent, if the attachment occurs at the reducing end residue. Increasingly complex structures in the vicinity of the branch point increase the population of the gauche–trans conformation of the C5–C6 bond. This population change is found to correlate with the 13C6 chemical shift.

Biocatalytic Synthesis of Maltodextrin-Based Acrylates from Starch and α-Cyclodextrin

Novel 2-(β-maltooligooxy)-ethyl (meth)acrylate monomers are successfully synthesized by CGTase from Bacillus macerans catalyzed coupling of 2-(β-glucosyloxy)-ethyl acrylate and methacrylate with α-cyclodextrin or starch. HPLC-UV analysis shows that the CGTase catalyzed reaction yields 2-(β-maltooligooxy)-ethyl acrylates with 1 to 15 glucopyranosyl units. (1) H NMR spectroscopy reveals that the β-linkage in the acceptor molecule is preserved during the CGTase catalyzed coupling reaction, whereas the newly introduced glucose units are attached by α-(1,4)-glycosidic linkages. The synthesized 2-(β-maltooligooxy)-ethyl acrylate monomers are successfully polymerized by aqueous free radical polymerization to yield the comb-shaped glycopolymer poly(2-(β-maltooligooxy)-ethyl acrylate).

Production of N-doped carbon nanotubes using α- and β-cyclodextrins: The effect of solubility

Carbon nanotubes (CNTs) doped with nitrogen (N) were prepared via a floating catalyst procedure using ferrocene (FcH), dimethylformamide (DMF) and cyclodextrin (CD) moieties in order to explore CD solubility effects on the preparation of nitrogen doped carbon nanotubes (N-CNTs). Two common types of CDs (α-CDs and β-CDs containing 6 and 7 glucopyranosyl units, respectively) were employed in the synthesis of ‘bamboo-shaped’ N-CNTs. The experimental data demonstrate that N-doping of the CNT lattice by the pyrolysis of CD molecules in DMF in the presence of Fe nanoparticles results in the incorporation of substitutional N into the C hexagonal network. Indeed, the structural configuration and physicochemical properties such as solubility and volatility of precursors influence the morphology of the final product (e.g. CNT diameters, yields, compartments sizes) in Fe catalyzed reactions through a series of decomposition processes.

Novel isolation of water-soluble polysaccharides from the fruiting bodies of Pleurotus ostreatus mushrooms

Novel water-soluble polysaccharides have been isolated from the fruiting bodies of the edible mushroom Pleurotus ostreatus. Three polysaccharide fractions were obtained by ethanol precipitation from cold water, hot water and hot aqueous NaOH extracts. The fractions were purified by size exclusion chromatography showing a unique carbohydrate occurring in each fraction: PC from the cold fraction, PH from the hot fraction and PB from the hot aqueous NaOH fraction. The analysis of the methylated alditol acetates and the NMR studies revealed that all the polysaccharides displayed a linear backbone. PC was formed by α-(1→3),(1→6)-linked galactopyranosyl residues whereas PH and PB consisted of glucose-linked units. PH was exclusively composed of glucopyranosyl units bound by α-(1→4) linkages whereas PB was a β-linked glucan showing (1→3) and (1→6) glycosidic bonds. The analysis of molecular arrangement by complexation with Congo red showed that only the β-linked polysaccharide (PB) displayed a triple helix conformation.

First Per-6-O-tritylation of Cyclodextrins

Because of the large dimension of the trityl group and the truncated conical geometry of cyclodextrin (CD) molecules, it is unclear if there is enough space at the narrower end of CDs to permit a per-6-O-tritylation. This work demonstrates that it is indeed possible to simultaneously install a trityl group at the O6-position of every glucopyranosyl unit in a CD. A novel per-6-substitution method has been developed for CD chemistry.

Structural characterization of polysaccharides isolated from grape stalks of Vitis vinifera L.

The main structural polysaccharides of grape stalks are cellulose, heteroxylan, and glucan. Cellulose contributes 30.3% of grape stalk matter and has an unusually high degree of the crystallinity (75.4%). Among hemicelluloses, xylan was the most abundant one, contributing ∼12% to the weight. The heteroxylan was isolated from the corresponding peracetic holocellulose by DMSO extraction followed by precipitation in ethanol. The Mw of heteroxylan (19.0kDa) was assessed by size exclusion chromatography (SEC) and the structure was inferred by methanolysis and methylation linkage analysis, as well as 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. The heteroxylan is a partially acetylated (DS=0.49) glucuronoxylan possessing the main backbone composed by β-(1→4)-linked d-xylopyranosyl units ramified with α-(1→2)-linked 4-O-methyl-α-d-glucuronosyl residues (MeGlcpA) at a molar ratio 25:1. The isolated heteroxylan contained concomitant β-glucan (ca. 15%), whose structure was elucidated by methylation linkage analysis and by NMR spectroscopy. The results obtained revealed mixed β-(1→3; 1→4)-d-glucan with a molar ratio of β-(1→3)- to β-(1→4)-linked glucopyranosyl units of 1:2.

Polyphasic Screening, Homopolysaccharide Composition, and Viscoelastic Behavior of Wheat Sourdough from a Leuconostoc lactis and Lactobacillus curvatus Exopolysaccharide-Producing Starter Culture

After isolation from different doughs and sourdoughs, 177 strains of lactic acid bacteria were screened at the phenotypic level for exopolysaccharide production on media containing different carbohydrate sources. Two exopolysaccharide-producing lactic acid bacteria (Lactobacillus curvatus 69B2 and Leuconostoc lactis 95A) were selected through quantitative analysis on solid media containing sucrose and yeast extract. The PCR detection of homopolysaccharide (gtf and lev) and heteropolysaccharide (epsA, epsB, epsD and epsE, and epsEFG) genes showed different distributions within species and strains of the lactic acid bacteria studied. Moreover, in some strains both homopolysaccharide and heteropolysaccharide genes were detected. Proton nuclear magnetic resonance spectra suggest that Lactobacillus curvatus 69B2 and Leuconostoc lactis 95A produced the same exopolysaccharide, which was constituted by a single repeating glucopyranosyl unit linked by an α-(1→6) glycosidic bond in a dextran-type carbohydrate. Microbial growth, acidification, and viscoelastic properties of sourdoughs obtained by exopolysaccharide-producing and nonproducing lactic acid bacterial strains were evaluated. Sourdough obtained after 15 h at 30°C with exopolysaccharide-producing lactic acid bacteria reached higher total titratable acidity as well as elastic and dissipative modulus curves with respect to the starter not producing exopolysaccharide, but they showed similar levels of pH and microbial growth. On increasing the fermentation time, no difference in the viscoelastic properties of exopolysaccharide-producing and nonproducing samples was observed. This study suggests that dextran-producing Leuconostoc lactis 95A and Lactobacillus curvatus 69B2 can be employed to prepare sourdough, and this would be particularly useful to improve the quality of baked goods while avoiding the use of commercially available hydrocolloids as texturizing additives.

Deciphering sulfoglycolipids of Mycobacterium tuberculosis

For 4 decades, in vivo and in vitro studies have suggested that sulfoglycolipids (SGLs) play a role in the virulence or pathogenesis of the tubercle bacilli. However, the SGL structure and biosynthesis pathway remain only partially elucidated. Using the modern tools of structural analysis, including MALDI-time-of-flight MS, MS/MS, and two-dimensional NMR, we reevaluated the structure of the different SGL acyl (di-, tri-, and tetra-acylated) forms of the reference strain Mycobacterium tuberculosis H37Rv, as well as those produced by the mmpL8 knockout strains previously described to intracellularly accumulate di-acylated SGL. We report here the identification of new acyl forms: di-acylated SGL esterified by simple fatty acids only, as well as mono-acylated SGL bearing a hydroxyphthioceranoic acid, which were characterized in the wild-type strain. In a clinical strain, a complete family of mono-acylated SGLs was characterized in high abundance for the first time. For the mmpL8 mutant, SGLs were found to be esterified i) by an oxophthioceranoic acid, never observed so far, and ii) at nonconventional positions in the case of the unexpected tri-acylated forms. Our results further confirm the requirement of MmpL8 for the complete assembly of the tetra-acylated forms of SGL and also provide, by the discovery of new intermediates, insights in terms of the possible SGL biosynthetic pathways.

Dynamic behaviour attributed to chiral carbohydrate substituents of N-heterocyclic carbene ligands in square planar nickel complexes

Nickel complexes having acetylated glucopyranosyl group incorporated N-heterocyclic carbene (NHC) ligands with methyl or benzyl groups as an N-substituent exhibit two kinds of dynamic behaviours in solution (1)H NMR spectroscopy. One of the dynamic behaviours is attributed to the anti- and syn-rotamers, which occur by the rotation of the unsymmetrical NHC ligands around the axes of the Ni-C bonds. The other is attributed to the diastereomers of the syn-rotamers, which occur by opposite rotation of the imidazolylidene rings and the chiral carbohydrate group incorporated into the NHC ligands. Crystallographic analysis of the nickel complex having the NHC ligand with acetylated glucopyranosyl and benzyl groups as N-substituents showed CH-π interaction between the glucopyranosyl unit of each NHC ligand and the phenyl ring of the other NHC ligand in the complex in the solid state.

ABA- and BAB-triblock cooligomers of tri-O-methylated and unmodified cello-oligosaccharides: syntheses and structure-solubility relationship

Triblock cooligomers consisting of tri-O-methyl-glucopyranosyl and unmodified glucopyranosyl residues, methyl 2,3,4,6-tetra-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-α-d-glucopyranoside (1: ABA triblock cooligomer; DS = 2.1) and β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-d-glucopyranose (2: BAB triblock cooligomer; DS = 1.8) were prepared. Compound 1 dissolved both in distilled water and chloroform but compound 2 dissolved in distilled water not in chloroform, though compounds 1 and 2 consist of 4 tri-O-methyl-glucopyranosyl and 2 unmodified anhydro glucopyranosyl units.

Lipase Nanogel Catalyzed Transesterification in Anhydrous Dimethyl Sulfoxide

The present work showed that Candida rugosa lipase, which is inactive in anhydrous dimethyl sulfoxide (DMSO), has been granted its original catalytic activity and greatly enhanced stability when encapsulated into a polyacrylamide nanogel. The molecular simulation and structural analysis suggested that the polyacrylamide nanogel shielded the extraction of essential water and maintained the native configuration of encapsulated lipase in anhydrous DMSO at an elevated temperature. The electron and fluorescence microscopy showed that the lipase nanogel would be well dispersed in anhydrous DMSO where its native counterpart aggregated. The encapsulated lipase behaved as a stable catalyst for transesterification between dextran and vinyl decanoate in anhydrous DMSO at 60 degrees C for 240 h and yielded a dextran-based polymeric surfactant with regioselectivity toward the C-2 hydroxyl group in the glucopyranosyl unit of dextran. All these indicated a high potential of enzyme nanogel for nonaqueous biocatalysis.