Agarose oligosaccharide- silver nanoparticle- antimicrobial peptide- composite for wound dressing.

Marine polysaccharides or oligosaccharides have potential to promote wound healing due to their biocompatibility and physicochemical properties. However, microbial infection delays wound healing process, and novel antimicrobial wound dressings are urgently needed. Here, agarose oligosaccharides (AGO) obtained from marine red algae were used as a reducing and stabilizer for green synthesis of silver nanoparticles (AgNPs), and further successfully connected with odorranain A (OA), one of antimicrobial peptides (AMPs), to obtain a novel composite nanomaterial (AGO-AgNPs-OA). Transmission electron microscopy (TEM) and Malvern particle size analyzer showed that AGO-AgNPs-OA was spherical or elliptic with average size of about 100 nm. Circular dichroism (CD) spectroscopy showed that AGO-AgNPs stabilized the α-helical structure of OA. AGO-AgNPs-OA showed stronger anti-bacterial activities than AGO-AgNPs, and had good biocompatibility and significant promoting effect on wound healing. Our data suggest that AMPs conjugated marine oligosaccharides and AgNPs may be effective and safe antibacterial materials for wound therapy.

Constrained saccharides: a review of structure, biology, and synthesis.

Review primarily covers from 1995-2018Carbohydrate function, recognized in a multitude of biological processes, provides a precedent for developing carbohydrate surrogates that mimic the structure and function of bioactive compounds. In order to constrain highly flexible oligosaccharides, synthetic tethering techniques like those exemplified by stapled peptides are utilized to varying degrees of success. Naturally occurring constrained carbohydrates, however, exist with noteworthy cytotoxic and chemosensitizing properties. This review highlights the structure, biology, and synthesis of this intriguing class of molecules.

Synthesis and Antigenicity against Human Sera of a Biotin-Labeled Oligosaccharide Portion of a Glycosphingolipid from the Parasite Echinococcus multilocularis.

Synthesis of a biotinylated analog of the carbohydrate portion of a glycosphingolipid from the parasite Echinococcus multilocularis has been achieved. We synthesized ß-D-Galp-(1→6)-ß-D-Galp-(1→6)-[α-L-Fucp-(1→3)]-ß-D-Galp-(1→R: biotin probe) (1) and compared the antigenicity by an enzyme linked immunosorbent assay (ELISA) with biotinylated trisaccharide α-D-Galp-(1→4)-ß-D-Galp-(1→3)-α-D-Galp-(1→R: biotin probe) (F), which has been shown to have significant antigenicity. Both of the oligosaccharides reacted with sera of alveolar echinococcosis (AE) patients, but showed different reactivity. Among the 60 sera of AE patients, more sera reacted with the linear sequence Galα1→4Galß1→3GalNAcα1→R of oligosaccharide (F) than for branched compound 1. Some sera showed high specificity to one of the compound, indicating that the antibodies in the sera of AE patients differ in their specificity to recognize carbohydrate sequences of glycosphingolipids. Our results demonstrate that both of the biotinylated oligosaccharides 1 and F have good serodiagnostic potential and are complementary to detect infections caused by the parasite Echinococcus multilocularis.

Human Milk Oligosaccharides and Synthetic Galactosyloligosaccharides Contain 3'-, 4-, and 6'-Galactosyllactose and Attenuate Inflammation in Human T84, NCM-460, and H4 Cells and Intestinal Tissue Ex Vivo.

BACKGROUND: The immature intestinal mucosa responds excessively to inflammatory insult, but human milk protects infants from intestinal inflammation. The ability of galactosyllactoses [galactosyloligosaccharides (GOS)], newly found in human milk oligosaccharides (HMOS), to suppress inflammation was not known. OBJECTIVE: The objective was to test whether GOS can directly attenuate inflammation and to explore the components of immune signaling modulated by GOS. METHODS: Galactosyllactose composition was measured in sequential human milk samples from days 1 through 21 of lactation and in random colostrum samples from 38 mothers. Immature [human normal fetal intestinal epithelial cell (H4)] and mature [human metastatic colonic epithelial cell (T84) and human normal colon mucosal epithelial cell (NCM-460)] enterocyte cell lines were treated with the pro-inflammatory molecules tumor necrosis factor-α (TNF-α) or interleukin-1ß (IL-1ß) or infected with Salmonella or Listeria. The inflammatory response was measured as induction of IL-8, monocyte chemoattractant protein 1 (MCP-1), or macrophage inflammatory protein-3α (MIP-3α) protein by ELISA and mRNA by quantitative reverse transcriptase-polymerase chain reaction. The ability of HMOS or synthetic GOS to attenuate this inflammation was tested in vitro and in immature human intestinal tissue ex vivo. RESULTS: The 3 galactosyllactoses (3'-GL, 4-GL, and 6'-GL) expressed in colostrum rapidly declined over early lactation (P < 0.05). In H4 cells, HMOS attenuated TNF-α- and IL-1ß-induced expression of IL-8, MIP-3α, and MCP-1 to 48-51% and pathogen-induced IL-8 and MCP-1 to 26-30% of positive controls (P < 0.001). GOS reduced TNF-α- and IL-1ß-induced inflammatory responses to 25-26% and pathogen-induced IL-8 and MCP-1 to 36-39% of positive controls (P < 0.001). GOS and HMOS mitigated nuclear translocation of nuclear transcription factor κB (NF-κB) p65. HMOS quenched the inflammatory response to Salmonella infection by immature human intestinal tissue ex vivo to 26% and by GOS to 50% of infected controls (P < 0.01). CONCLUSION: Galactosyllactose attenuated NF-κB inflammatory signaling in human intestinal epithelial cells and in human immature intestine. Thus, galactosyllactoses are strong physiologic anti-inflammatory agents in human colostrum and early milk, contributing to innate immune modulation. The potential clinical utility of galactosyllactose warrants investigation.

[In vitro antitumor activity of heterochitooligosaccharides (a review)].

This review presents an analysis of the literature data over the last decade in order to reveal the relationship between the structure and composition of chitin/chitosan oligomers and their antitumor activity. Oligosaccharides consisting of N-acetylglucosamine and/or glucosamine units connected to each other by ß-1,4-O-glycoside bond are generally called chitooligosaccharides. Homochitooligosaccharides are the oligomers of N-acetylglucosamine (AGA) or glucosamine (GA). Heterooligosaccharides are a mixture of various oligomers differing in the degree of polymerization (DP), acetylation (DA), or deacetylation (DD), as well as in the location of N-acetyl residues in the oligomer chain. Heterochitooligomers with a polymerization degree of no more than 10 are usually water soluble. The solubility of chitooligosaccharides with a DP of more than 10 depends on the DA and pH of a solution. The pharmaceutical and food industries, as well as scientists engaged in basic research, are interested in the use of heterochitooligosaccharides. This is explained by their unique properties, such as good water solubility; minimal toxicity; biocompatibility; the ability to penetrate cell membranes, resulting in a high degree of absorption (unlike chitin and chitosan); and their biological activity. Therefore, in the last decade, researchers have focused their attention on studying the relationship of the structure of oligosaccharides and their specific activity, such as antitumor, antimicrobial, antioxidant, immunemodulatory, and other activities. This is shown by the number of publications, which has doubled compared to the number in 2001.

Synthesis of the Tetrasaccharide Repeating Unit from Acinetobacter baumannii Serogroup O18 Capitalizing on Phosphorus-Containing Leaving Groups.

The first convergent synthesis of the tetrasaccharide repeating unit of the polymeric O antigen isolated from Acinetobacter baumannii serogroup O18 has been achieved. The ManNAcß1→4Gal and GalNAcß1→3Gal units were successfully obtained through ß-selective glycosylation with 2-azido-4,6-O-benzylidene-2-deoxymannosyl diphenyl phosphate and Tf2NH-promoted glycosylation with 2-acetamido-2-deoxygalactosyl diethyl phosphite, respectively. The disaccharide units could be coupled with the aid of TMSClO4 as an activator of the diphenyl phosphate leaving group, and global deprotection completed the synthesis of the tetrasaccharide.

Effect of pretreatments and endo-1,4-ß-xylanase hydrolysis of canola meal and mustard bran for production of oligosaccharides.

Alkali/acid-pretreated canola meal and mustard bran were subjected to endo-1,4-ß-xylanase (T. longibrachiatum) hydrolysis for oligosaccharide production. Pretreatments significantly (α = 0.05) increased the relative content of pentose sugars, especially in alkali-pretreated canola meal (∼44 %) and mustard bran (∼72 %). The amounts of pentosan (g/100 g) in acid- and alkali-pretreated canola meal were 7.50 and 8.21 and in corresponding mustard bran were 8.67 and 10.39, respectively. These pretreated substrates produced a pentose content (g/100 g) of 2.10 ± 0.14 (18 h) and 2.95 ± 0.10 (24 h), respectively, during hydrolysis. As per UPLC-MS data, the main oligosaccharides in the hydrolyzates of alkali-pretreated substrates are xylo-glucuronic acid and xylobiose. The release of total phenolics of the hydrolyzates increased until 18 h irrespective of the type of substrate or pretreatment. Hydrolyzates of acid-pretreated substrates indicated more total antioxidant activity than alkali-pretreated substrates, attributed to its high phenolic content. The study suggests the potential of canola meal and mustard bran for the production of oligosaccharides, wherein the use of various combinations of cell-wall-degrading enzymes and its optimization may result in a better yield, with simultaneous production of endogenous phenolics.

Synthetic disialyl hexasaccharides protect neonatal rats from necrotizing enterocolitis.

Two novel synthetic α2-6-linked disialyl hexasaccharides, disialyllacto-N-neotetraose (DSLNnT) and α2-6-linked disialyllacto-N-tetraose (DS'LNT), were readily obtained by highly efficient one-pot multienzyme (OPME) reactions. The sequential OPME systems described herein allowed the use of an inexpensive disaccharide and simple monosaccharides to synthesize the desired complex oligosaccharides with high efficiency and selectivity. DSLNnT and DS'LNT were shown to protect neonatal rats from necrotizing enterocolitis (NEC) and are good therapeutic candidates for preclinical experiments and clinical application in treating NEC in preterm infants.

Preparation of inulin-type fructooligosaccharides using fast protein liquid chromatography coupled with refractive index detection.

A fast protein liquid chromatography coupled with refractive index detection (FPLC-RID) method was firstly developed for preparation and purification of fructooligosaccharides with different degree of polymerization from burdock, Arctium lappa. After extraction with 60% ethanol and decolorization with MCI gel CHP20P, total fructooligosaccharides were purified on Bio-Gel P-2 column eluted with water at the flow rate of 0.3 ml/min, which was the optimized conditions. The obtained fructooligosaccharides with degree of polymerization of 3-9 were identified based on their methylation analysis, MS and NMR data. This method has the advantages of high automation, good recovery and easy performance, which could be used for preparation of FOS from other sources, as well as other targeted compounds without UV absorbance.

Synthesis of oligosaccharide fragments of the rhamnogalacturonan of Nerium indicum.

Three trisaccharides, one pentasaccharide, and one heptasaccharide, namely α-D-GalA-(1→2)-α-L-Rha-(1→4)-ß-D-GalA-OC3H7 (1), α-L-Rha-(1→4)-α-D-GalA-(1→4)-ß-D-GalA-OC3H7 (2), α-D-GalA-(1→4)-α-D-GalA-(1→2)-α-L-Rha-OC3H7 (3), α-D-GalA-(1→2)-α-L-Rha-(1→4)-α-D-GalA-(1→2)-α-L-Rha-(1→4)-ß-D-GalA-OC3H7 (4), and α-D-GalA-(1→2)-α-L-Rha-(1→4)-α-D-GalA-(1→2)-α-L-Rha-(1→4)-α-D-GalA-(1→2)-α-L-Rha-(1→4)-ß-D-GalA-OC3H7 (5), which are relevant to the fragments of the rhamnogalacturonan of Nerium indicum, were concisely synthesized. The syntheses feature highly stereoselective formation of the α-D-GalA-linkage with GalA N-phenyltrifluoroacetimidates as donors.

Chemistry and biology of oligovalent ß-(1→2)-linked oligomannosides: new insights into carbohydrate-based adjuvants in immunotherapy.

A series of oligovalent carbohydrate assemblies (ranging from mono- to pentavalent), derived from three structurally different ß-linked or ß-(1→2)-linked mannosides, has been chemically synthesized, and the respective compounds have been biologically evaluated in order to investigate their immunostimulatory properties. The Crich methodology for ß-mannosylation was successfully utilized to introduce the ß-linkages, and a click chemistry protocol was utilized to generate the oligovalent derivatives. A convenient protecting group strategy involving the simultaneous use of both p-methoxybenzyl and benzylidene groups was employed, which allowed a simple and cost-effective global deprotection step. The immunomodulatory properties of the synthesized multivalent mannosides were evaluated by assessing cytokine production in human white blood cell cultures. The Th2-type cytokines interleukin-4 and interleukin-5 (IL-4 and IL-5), the Th1 cytokine interferon-γ (IFN-γ), the Treg cytokine IL-10, and the pro-inflammatory cytokine tumor necrosis factor (TNF) were included in the screening. A single trivalent acetylated mannobiose derivative was identified as a potent inducer of Treg and Th1 immune response, resulting in strong IL-10 and moderate IFN-γ productions dose-dependently, while inducing no Th2 cytokine response. The immunomodulatory properties of this trivalent mannoside were further studied in vitro in allergen (Bet v)-stimulated human peripheral blood mononuclear cell cultures of birch pollen allergic subjects. Stimulation with birch pollen induced strong IL-4 and IL-5 responses, which could be suppressed by the trivalent acetylated mannobiose derivative. The IL-10 response was also suppressed, whereas the production of IFN-γ was strongly enhanced. The results suggest that the identified lead compound has suppressive effects on the Th2-type allergic inflammatory response and shows potential as a possible lead adjuvant for the specific immunotherapy of allergies.

Pectic-oligosaccharides prepared by dynamic high-pressure microfluidization and their in vitro fermentation properties.

Pectic-oligosaccharides (POSs) were prepared from apple pectin by dynamic high-pressure microfluidization (DHPM). Operating under selected conditions (pectin concentration 1.84%, solution temperature 63 °C, DHPM pressure 155MPa and number of cycles 6 passes), 32.92% of the pectin was converted into POS. The resulting POS contains 29.56% galacturonic acid and 58.53% neutral sugars. The prebiotic properties of POS were then evaluated using a fecal batch culture fermentation. The POS increased the number of Bifidobacteria and Lactobacilli, and produced a higher concentration of acetic, lactic, and propionic acid than their parent pectin. Furthermore, POS decreased the number of Bacteroides and Clostridia while their parent pectin increased them. Moreover, the effects of POS on the growth of these bacteria and production of short-chain fatty acids are comparable to those of the most studied prebiotic, fructooligosaccharide. These results indicated that the POS prepared by DHPM has a potential to be an effective prebiotic.

Uronic acids in oligosaccharide and glycoconjugate synthesis.

This chapter describes the assembly of uronic acid containing oligosaccharides and glycoconjugates. Two strategies are available to access these target molecules, namely a pre-glycosylation oxidation approach, in which uronic acid building blocks are used, and a post-glycosylation oxidation strategy, which employs an oxidation step after the assembly of the oligosaccharide chain. Because uronic acid building blocks are generally considered to be less reactive than their non-oxidized counterparts, the latter approach has found most application in carbohydrate synthesis. With the aid of selected examples of recent syntheses of biologically relevant oligosaccharides and glycoconjugates, the reactivity of different uronic acid building blocks is evaluated. From these examples it is apparent that the generally assumed low reactivity of uronic acids does not a priori rule out an efficient assembly of these target compounds. Besides influencing the reactivity of a given pyranoside, the C-5 carboxylic acid function can also have a profound effect on the stereochemical course of a glycosylation reaction, which can be exploited in the stereoselective formation of glycosidic bonds.

Biological properties of (1 → 3)-ß-D-glucan-based synthetic oligosaccharides.

Despite the fact that ß-glucans are well-established immunomodulators, the problems with batch-to-batch heterogeneity remains problematic. The aim of this study was to prepare and evaluate new type of synthetic oligosaccharides. A new family of oligo-(1 → 3)-ß-d-glucans modified on the reducing end was synthesized using a controlled and specific inversion of configuration at C-2 starting from already formed oligo-(1 → 3)-ß-d-glucans. The designed glycosides are characterized by the presence of four or five glucopyranose entities and a mannose residue at the reducing end. To study of the impact of well-defined structural modulations, we used murine and human models to evaluate their immunostimulating potential. These novel oligosaccharides showed strong and long-lasting stimulation of phagocytosis and significant potentiation of synthesis and/or secretion of interleukin (IL-2, IL-4, IL-5, IL-6), tumor necrosis factor-α, and vascular endothelial growth factor. In addition, the oligosaccharides tested showed significant effects on expression of several genes in human fibroblasts and breast cancer cells. From our results it is clear that these synthetic oligosaccharides represent a better alternative to natural ß-glucans.

Development of idraparinux and idrabiotaparinux for anticoagulant therapy.

Idraparinux is an analogue of fondaparinux binding with high affinity to antithrombin. It was designed for weekly, rather than daily, administration, with an exceptionally long half-life. One potential problem with small heparin-like fragments of this type is the difficulty of neutralising excessive activity in the case of side-effects or overdose. The efficacy of idraparinux was was proven in clinical studies with patients suffering from venous thromboembolism (VTE) or atrial fibrillation. Due to major bleeding events during treatment for more than six months the development of idraparinux was stopped. Idrabiotaparinux has an attached biotin moiety at the non-reducing end unit, which allows its neutralisation with avidin, an egg-derived protein with low antigenicity. This compound is currently investigated in clinical trials for prevention of recurrent VTE in patients with acute pulmonary embolism. The future of idrabiotaparinux depends also on the safety and efficacy of avidin.

Synthesis of rhamnogalacturonan I fragments by a modular design principle.

The improved syntheses of methyl 2-O-acetyl-3-O-benzyl-alpha-L-rhamnopyranoside (12) and 1,2-di-O-acetyl-3-O-benzyl-alpha-L-rhamnopyranose (15), which were used as glycosyl acceptor and donor, respectively, are described. Glycosylation of the O-4 position of both rhamnose derivatives with 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl bromide (26) provided disaccharides 27 and 29. After partial deprotection of 27 and coupling of the resulting 28 with disaccharide 19, tetrasaccharide 31 was obtained. Furthermore, transforming of 29 into the corresponding bromide 30 and coupling with galacturonates 16 and 32 provided trisaccharides 33 and 34, respectively, which could be regarded as building blocks of ramified rhamnogalacturonan fragments. The preparation of tetra- (21) and hexasaccharide (25) of rhamnogalacturonan I is reported to demonstrate the feasibility of the synthesis of larger pectin fragments using the modular design principle with this type of building blocks.

Synthesis and structure verification of the vaccine adjuvant QS-7-Api. Synthetic access to homogeneous Quillaja saponaria immunostimulants.

QS-7-Api is an exceedingly potent immuno-adjuvant isolated from the bark of Quillaja saponaria. It is significantly less toxic than QS-21, a related saponin that is currently the favored adjuvant in anticancer and antiviral vaccine clinical trials. Tedious isolation/purification protocols and uncertainty in its structural constitution have hindered the clinical development of QS-7. A chemical synthesis of QS-7-Api is described, providing structural verification of the adjuvant. A novel semisynthetic sequence to QS-7-Api has also been established, greatly facilitating access to QS-7 for preclinical and clinical evaluation.

Synthesis of two repeat units corresponding to the backbone of the pectic polysaccharide rhamnogalacturonan I.

A tetrasaccharide corresponding to a sequence of the rhamnogalacturonan I backbone has been synthesized. This synthesis relies on only two protected monosaccharides and proceeds through a common disaccharide intermediate. Synthesis of this tetrasaccharide has been designed to allow for the addition of branching elements at the 4-positions of the rhamnosyl units, or further chain elongation at the 2-position.

Inulin-type prebiotics--a review: part 1.

This article is part 1 of a two-part review of inulin-type prebiotics. Prebiotics are a category of nutritional compounds grouped together by the ability to promote the growth of specific beneficial (probiotic) gut bacteria. Inulin-type prebiotics contain fructans of the inulin-type. Fructans are a category of nutritional compounds that encompasses naturally occurring plant oligo- and polysaccharides in which one or more fructosyl-fructose linkages comprise the majority of glycosidic bonds. To be inulin-type a fructan must have beta (2(1) fructosyl-fructose glycosidic bonds, which gives inulin its unique structural and physiological properties, allowing it to resist enzymatic hydrolysis by human salivary and small intestinal digestive enzymes. Inulin-type prebiotics include fructooligosaccharides (FOS), oligofructose, and inulin - terms that have been used inconsistently in both the scientific literature and in food applications. Commercially available inulin-type prebiotics can be extracted from food (typically chicory root) or synthesized from a more fundamental molecule (typically sucrose). Depending on the starting source and degree of processing, inulin-type prebiotics can be produced with very different chemical compositions. Some inulin-type prebiotics are relatively high in free sugars (the monosaccharides fructose and glucose and the disaccharide sucrose), while others have most or all free sugars removed. Processing can also result in mixes consisting exclusively of inulin-type oligosaccharides, polysaccharides, or both. Because inulin, oligofructose, and FOS resist enzymatic digestion in the upper gastrointestinal tract, they reach the colon virtually intact where they undergo bacterial fermentation. All inulin-type prebiotics are bifidogenic - stimulating the growth of Bifidobacteria species. The effects they have on other gut organisms are less consistent. A minimal dose of inulin-type prebiotic appears to be needed to produce a bifidogenic effect. However, intra-individual response to an identical dose of the same inulin-type prebiotic, in terms of stimulation of total number of Bifidobacteria and individual Bifidobacteria species, can be variable. Research on therapeutic uses of inulin-type prebiotics will be covered in part 2 of this review.