Preparation and properties of glucosamine and carboxymethylchitin from shrimp shell

D-Glucosamine is a Potential Urease Inhibitor from Middle Eastern Medicinal Plants for Combatting Helicobacter Pylori Infections; a Molecular Docking and Simulation Approach

Helicobacter pylori stands as a significant risk factor for both peptic and stomach ulcers. Their resistance to the highly acidic host environment primarily stems from their capability to produce urease, an enzyme that rapidly converts urea into NH3 and CO2. These byproducts are crucial for the bacterium's survival under such harsh conditions. Given the pivotal role of medicinal plants in treating various ailments with minimal side effects, there is an urgent need for a natural drug that can effectively eliminate H. pylori by inhibiting urease. Hence, the current study aims to identify the most potent urease inhibitor among the natural compounds found in Middle Eastern medicinal plants, taking into consideration factors such as optimal affinity, drug-like properties, pharmacokinetic characteristics, and thermodynamic attributes. In total, 5599 ligand conformers from 151 medicinal plants were subjected to docking against the urease's active site. The top-ranking natural compounds, as determined by their high docking scores, were selected for further analysis. Among these compounds, D-glucosamine (PubChem code 439,213) exhibited the most interactions with the crucial amino acid residues in the urease's active site. Furthermore, D-glucosamine demonstrated superior absorption, distribution, metabolism, excretion, and toxicity properties compared to other top-ranked candidates. Molecular dynamics simulations conducted over 100 nanoseconds revealed stable root mean square deviations and fluctuations of the protein upon complexation with D-glucosamine. Additionally, the radius of gyration and solvent-accessible surface area values for the D-glucosamine-urease complex were notably lower than those observed in other typical urease-inhibitor complexes. In conclusion, this study provides valuable insights into the potential development of D-glucosamine as a novel urease inhibitor. This promising compound holds the potential to serve as an effective drug for combating H. pylori infections in the near future.

Design, Synthesis, and Antifungal Activities of Hymexazol Glycosides Based on a Biomimetic Strategy

Hymexazol (HYM) is irreplaceable for treating soil-borne diseases due to its high efficiency and low cost, as a broad-spectrum fungicide. However, when HYM is absorbed by plants, it is rapidly converted into two glycoside metabolites, and the antifungal activities of these glycosides are inferior to that of HYM. Therefore, in this study, to maintain strong antifungal activity in vitro and in vivo, HYM was glycosylated with amino sugars that have diverse biological activities to simulate plant glycosylation. The antifungal experiment proved that glycoside 15 has the highest antifungal activity, and N-acetyl glucosamine and HYM had obvious synergistic effects. According to the structure-activity relationship studies, glycoside 15 had greater numbers of active electron-rich regions and front-line orbital electrons due to the introduction of N-acetyl glucosamine. Moreover, glycoside 15 can significantly promote plant growth and induce an increase in plant defense enzyme activity. Additionally, compared to HYM, the results of electron microscopy and proteomics revealed that glycoside 15 has a unique antifungal mechanism. The promising antifungal activity and interactions with plants mean that glycoside 15 is a potential green fungicide candidate. Furthermore, this research conducted an interesting exploration of the agricultural applications of amino sugars.

Green synthesis of glyco-phenol by enzymatic coupling between ferulic acid and glucosamine: An ecofriendly procedure

A new glyco-phenol was produced by the coupling between glucosamine (Glu) and ferulic acid (FA) using Myceliophthora thermophila laccase as biocatalyst in mild conditions (distilled water and 30°C) as an environmentally friendly process. Results indicated that the enzymatic reaction created a new derivative (FA-Glu), produced from coupling between Glu and FA by covalent bonds. By the high production of (FA-Glu) derivative and its stability, the optimal ratio of (FA:Glu) was of (1:1) at optimal time reaction of 6 h. Under these optimal conditions, almost 55% of -NH₂ groups on Glu were bound with FA oxidation products. The new derivative showed higher hydrophobic character than Glu due to the presence of FA in its structure. Liquid chromatography-mass spectrometry analysis showed that (FA-Glu) derivative exhibited a molecular mass at MM 713 g/mol containing one Glu molecule and three FA molecules after decarboxylation. Furthermore, the new derivative presented good antioxidant and antiproliferative activities in comparison with Glu and FA. These results suggest that the enzymatic conjugation between Glu and FA is a promising process to produce a new glyco-phenol having good functional properties for potential applications.

Chitosan as a chiral ligand and organocatalyst: preparation conditions–property–catalytic performance relationships

Properties of chitosan prepared by alkaline deacetylation of chitin under various conditions were correlated with their performance as ligands or organocatalysts in asymmetric catalytic reactions.

Investigation of the Effects of Molecular Parameters on the Hemostatic Properties of Chitosan

Hemorrhea is one of the major problems in war, trauma care, and surgical operation that threaten the life of the injured and patients. As a novel polymeric hemostatic agent, biodegradable chitosan can stop bleeding through a variety of approaches. In this paper, chitosan with various molecular parameters was prepared from chitin as raw material through deacetylation, oxidative degradation, hydrophilic modification, and salt formation reactions. The influence of different polymer parameters on the hemostatic effects of chitosan was investigated by in vitro coagulation time and dynamic coagulation assay. The results showed that when the molecular weights were high (10⁵⁻10⁶) and approximate, the coagulation effect of chitosan improved with a decrease of the deacetylation degree and achieved a prominent level in a moderate degree of deacetylation (68.36%). With the same degree of deacetylation, the higher the molecular weight of chitosan, the better the procoagulant effect. The substituent derivatives and acid salts of chitosan showed significant procoagulant effects, especially the acid salts of chitosan. In addition, the hemostasis mechanism of chitosan with various parameters was preliminarily explored by analyzing the plasma recalcification time (PRT). The efforts in this paper laid a basis for further study of the structure⁻activity relationship and the mechanism of chitosan hemostasis.

Guanidination of soluble lysine-rich cyanophycin yields a homoarginine-containing polyamide

Soluble cyanobacterial granule polypeptide (CGP), especially that isolated from recombinant Escherichia coli strains, consists of aspartic acid, arginine, and a greater amount of lysine than that in insoluble CGP isolated from cyanobacteria or various other recombinant bacteria. In vitro guanidination of lysine side chains of soluble CGP with o-methylisourea (OMIU) yielded the nonproteinogenic amino acid homoarginine. The modified soluble CGP consisted of 51 mol% aspartate, 14 mol% arginine, and 35 mol% homoarginine. The complete conversion of lysine residues to homoarginine was confirmed by (i) nuclear magnetic resonance spectrometry, (ii) coupled liquid chromatography-mass spectrometry, and (iii) high-performance liquid chromatography. Unlike soluble CGP, this new homoarginine-containing polyamide was soluble only under acidic or alkaline conditions and was insoluble in water or at a neutral pH. Thus, it showed solubility behavior similar to that of the natural insoluble polymer isolated from cyanobacteria, consisting of aspartic acid and arginine only. Polyacrylamide gel electrophoresis revealed similar degrees of polymerization of the native (12- to 40-kDa) and modified (10- to 35-kDa) polymers. This study showed that the chemical structure and properties of a biopolymer could be changed by in vitro introduction of a new functional group after biosynthesis of the native polymer. In addition, the modified CGP could be digested in vitro using the cyanophycinase from Pseudomonas alcaligenes strain DIP1, yielding a new dipeptide consisting of aspartate and homoarginine.

Chitin

A comprehensive profile of chitin with 61 references is reported. A full description including nomenclature, formulae, elemental analysis, and appearance is included. Methods of preparation for chitin and its derivative, such as chitosan, are discussed. Physical properties, analytical methods, uses and applications, stability, biodegradability, and toxicity of chitin are also reviewed.

Preparation and characterization of carboxymethylated beta-chitins and their abilities of moisture absorption and retention

Carboxymethyl chitins (CM-chitins) with a high degree of substitution (DS), a low degree of deacetylation (DD), and high molecular weight were prepared directly from beta-chitin and characterized using (1)H NMR, FT-IR, TA, potentiometric titration, and elemental analysis methods. CM-chitins with different molecular weight were prepared using ultrasonic degradation method. Their abilities of moisture absorption and retention were investigated. The moisture-absorption ratio and moisture-retention ratio of CM-chitins increased as their DS increased. The moisture-absorption ratio and moisture-retention ratio of CM-chitins with high DS were close to that of hyaluronic acid (HA). The effect of molecular weight (>10(6)) of CM-chitin on its moisture-absorption ratio and moisture-retention ratio is neglectable.