Carbohydrate Research最新文献

Elucidating the molecular mechanisms of chemical O-glycosylation remains a significant challenge in glycochemistry. This study examines the mechanism of the nucleophilic substitution reaction between glycosyl triflates, which are extensively used in studies of glycosylation mechanisms, and several acceptor alcohols. The investigation was conducted through a comparative analysis of permethylated glucosyl triflate GTf and its xylosyl counterpart XTf. The glycosylation reactions, conducted in dichloromethane using GTf and XTf with EtOH, tBuOH, and CF₃CH₂OH, exhibited diverse α/β selectivities depending on the types of donor and acceptor molecules used. Identifying a unified mechanism to explain this range of selectivities proved challenging. Notably, we observed a distinct trend wherein the addition of excess triflate salt (Bu₄NOTf) had a more pronounced effect on the α/β selectivity in glycosylation reactions utilizing XTf compared to those using GTf. Quantum chemical calculations performed at the SCS-MP2//DFT(M06-2X) level, with explicit inclusion of five solvent molecules, showed that contact ion pairs arising from XTf were significantly more stable than those from GTf. These experimental and computational results strongly suggest that ion pairs play a more crucial role in the glycosylation process involving XTf than GTf. Additionally, our quantum chemical analyses clarified that the enhanced stability of the ion pairs from XTf was attributed not to the strength of the C-1−OTf bond within XTf but to the flexibility in the conformational changes of XTf's pyranosyl ring.

We describe the synthesis of the full set of the so far unknown methyl altrobiosides and the initial analysis of the conformational dynamic which occurs in some of the synthesized compounds. d-Altrose chemistry has largely been neglected as it is a rare sugar and has first to be synthesized from glucose or mannose, respectively. Nevertheless, d-altrose is particularly interesting as the energy barrier between the complementary chair conformations is rather low and therefore dynamic mixtures of conformers might occur. We describe the ready synthesis of the selectively protected altrosyl acceptors for the glycosidation from d-mannose and the altrosyl-trichloroacetimidate as useful glycosyl donor to achieve the (1 → 2), (1 → 3), (1 → 4), and (1 → 6)-α-linked altrobiosides. The diastereomeric α- and β-O-(d-altropyranosyl)-trichloroacetimidates adopt different ring conformations as analyzed by NMR and VCD spectroscopy. Also, the pyranose ring conformations of the obtained altrobiosides apparently differ from a regular ⁴C₁ chair according to NMR analysis and are influenced by the regiochemistry of the interglycosidic linkage.

Liver cancer is the third leading cause of cancer deaths globally. The use of Hydroxycamptothecin (HCPT) as a first-line chemotherapeutic agent for liver, lung, and gastric cancers is often hampered by its low activity, limited targeting, and poor water solubility. This results in a low accumulation of HCPT in tumor cells, as well as the inability to maintain continuous treatment. Consequently, there is an urgent need to develop an accessory method that can enhance the therapeutic efficacy of HCPT while exhibiting good biocompatibility and targeted delivery ability. To address this critical issue, an enzyme-triggered supramolecular nanocarrier, refer as SCD/LCC SNCs, has been successfully developed, leveraging the aggregation of the negatively charged sulfate-modified β-CDs and positively charged lauroylcholine chloride (LCC). This nanocarrier demonstrates acetylcholinesterase (LCC) triggered decomposition behavior, making it a promising drug carrier for HCPT. The cellular assays conducted have demonstrated that HCPT loaded into these SCD/LCC SNCs exhibit reduced cytotoxicity towards normal cells while maintaining robust tumor inhibitory activity and inducing apoptosis. Therefore, this study offers a promising strategy for the effective use of HCPT in the treatment of liver cancer.

Fig fruit is widely accepted in warm and tropical regions due to the sweet taste and health benefits. The polysaccharides in fig fruit are responsible for the health benefits. However, information regarding polysaccharide structure remains limited. In this study, the water-soluble polysaccharides (FFP) were extracted from fig fruit with a yield of 15.3 mg/g. Anion exchange chromatography and gel permeation chromatography were used for purification. A leading polysaccharide was purified and characterized as below. The monosaccharide composition of FFP included arabinose (Ara), galactose (Gal), galacturonic acid (GalA) and rhamnose (Rha). The glycosidic linkages were revealed to be L-Ara-(1→, →5)-L-Ara-(1→, →2,4)-L-Rha-(1→, →2)-L-Rha-(1→, →4)-D-Gal-(1→ and D-Gal-(1 → . Nuclear magnetic resonnance (NMR) spectra revealed that FFP had →4)-α-D-GalpA-(1 → 2)-α-L-Rhap-(1→ as backbone. The side chains included Galp-β-D-(1 → 4)-Galp-β-D-(1 → 4)-Galp-β-D-(1 → 4)-Galp-β-D-(1→ and α-L-Araf-(1 → 5)-α-L-Araf-(1 → . They were linked to C-4 of Rhap. FFP inhibited the production of NO, IL-6 and IL-1β levels induced by LPS. IL-6 and IL-1β levels were returned to normal. These information are helpful to understand this functional fruit.

The importance of Gellan gum has been increasing gradually and its unique characteristics are suitable for various advanced food technologies. This review outlines recent developments in gellan gum production, modification, and newer applications focusing on food printing and bioactive delivery applications, in the last three years. The yield and production condition of gellan gum is a major factor that affects the cost and its applications. Moreover, modified Gellan gum has been shown to have superior characteristics and functionality as compared to native one. The viscosifying, thermosensitive, gelling etc. characteristics of gellan gum makes it an crucial ingredient in case of preparation of 3D printing ink. Further, gellan gum is also found to be important wall material in case of bioactive delivery application through encapsulation. Optimized methods of production, sustainable feedstock, and stress conditions are critical for the desired functionality and yield of the Gellan gum.

A series of new 1,2,3-triazole fused chromene based glucose triazole conjugates were synthesized from chromene fused 1,2,3-triazolyl extended alkyne and 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl azide in good to excellent yield by a copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The major advantages include mild reaction conditions, high yield, good substrate scope, and shorter reaction time. The antibacterial efficacy of the compounds were assessed in vitro against human pathogenic Gram-negative E. coli and Gram-positive S. aureus bacteria. Compound 24j was found to be the most potent molecule with zone of inhibition (ZI) of 17 mm and minimum inhibitory concentration (MIC) of 25 μg mL⁻¹ in E. coli and ZI of 16 mm and MIC of 25 μg mL⁻¹ in S. aureus. Also, it significantly inhibited E. coli DNA-gyrase in silico with a binding affinity of −9.4 kcal/mol. Among all the synthesized compounds, 24i, 24d, 24e and 24f showed significant antibacterial activity against both strains and inhibited DNA-gyrase in silico with good binding affinities. Hence, these 1,2,3-triazole fused chromene based glucose triazole conjugates may evolve to be powerful antibacterial agents in recent future, according to structure-activity relationships based on strong antibacterial properties and molecular docking studies.

Glycolipids incorporating positive charges, mediated by an imidazolium cation, have shown potential for effective formulation of vesicular drug carriers, reflecting repulsive electrostatic forces, promoting the formation of nanosized assemblies and preventing unwanted Oswald ripening (Goh et al. (2019), ACS Omega 4, 17,039). Our continuous development of an assembly-based drug delivery system prompted us to investigate a pH-sensitive analogue, leading to the synthesis of a 6-amino-Guerbet glycoside. However, in contrast to the imidazolium counterpart, the amine-mediated charge increased the intermolecular cohesions, furnishing bigger assemblies instead, which further increased upon introduction of acid. Moreover, assemblies exhibited a significantly reduced positive charge density. It is concluded that strong proton-initiated hydrogen bonding between amino groups provide cohesive head group interactions overcompensating possible repulsive charge interactions. While this behavior invalidates the application of the amino-glucoside as dispersing agent for the formulation of small vesicles, it potentially paves a route towards enhanced vesicle stability.

The DIBAL-H reduction of the Baylis-Hillman sugar adduct, obtained from 3-O-benzyl-1,2-isopropylidene-α-D-xylo-pentodialdo-1,4-furanose yielded trisubstituted alkenes by eliminating the β-hydroxyl group. Subsequently, the hydrolysis of the isopropylidene acetal to the corresponding hemiacetal was reacted with N-benzyl hydroxylamine hydrochloride to generate the nitrone, which underwent diastereoselective intramolecular 1,3-dipolar nitrone olefin cycloaddition (INOC) to give an isoxazolidine skeleton. The concomitant reductive cleavage of the N-O bond and benzyl group of the fused isoxazolidines afforded new functionalized aminocyclopentitols in good yields.

Hyaluronidases are a class of enzymes that can degrade hyaluronic acid and have a wide range of applications in the medical field. In this study, the marine bacterium Vibrio sp. ZG1, which can degrade HA, was isolated, leading to the discovery of two novel hyaluronan lyases, Vhylzx1 and Vhylzx2, through genome sequencing and bioinformatic analysis. These lyases belong to the polysaccharide lyase-8 family. Vhylzx1 and Vhylzx2 specifically degrade HA, with highest activity at 35 °C, pH 5.7 and 50 °C, pH 7.1. Vhylzx1 and Vhylzx2 are endo-type enzymes that can fully degrade HA into unsaturated disaccharides. Sequence homology assessment and site-directed mutagenesis revealed that the catalytic residues of Vhylzx1 are Asn²³¹, His²⁸¹, and Tyr²⁹⁰, and that the catalytic residues of Vhylzx2 are Asn²²⁷, His²⁷⁷, and Tyr²⁸⁶. Moreover, this study used consensus sequences to enhance the specific activity of Vhylzx2 mutants. Notably, the mutants V564I, N742D, L619F, and D658G increases the specific activity by 2.4, 2.2, 1.3, and 1.2-fold. These characteristics are useful for further basic research and applications, and have a promising application in the preparation of biologically active hyaluronic acid oligosaccharides.

Chitosan is a natural and renewable polysaccharide that can form biopolymers. It is derived from the deacetylation of chitin mainly from crustaceans' shells, but also from fungi and insects. Thanks to unique characteristics such as antimicrobial effects, antioxidant properties or film forming capacities, it has triggered an important amount of research in the last decade about possible applications in industrial fields. The main application field of chitosan is the food industry where it can be used for preservation purposes and shelf-life improvement for fresh food products such as fruits or meat. For beverages, it is used for clarification and fining as well as elimination of spoilage flora in beverages like fruit juices or wine. And in agriculture, it can be used as a plant protection product through different mechanisms like the elicitation of plant defences. The mechanisms of action of chitosan on microorganisms are multiple and complex but revolve mostly around the disturbance of microorganisms’ membranes and cell walls resulting in the leakage of cell material. The use of chitosan is still minor but is promising in finding environmentally friendly alternatives to synthetic chemicals and plastics. Therefore, its characterization is primordial for the future of sustainable production and preservation processes.