1 H NMR studies of molecular interaction of D-glucosamine and N -acetyl-D-glucosamine with capsaicin in aqueous and non-aqueous media

Understanding the Molecular-Level Interactions of Glucosamine-Glycerol Assemblies: A Model System for Chitosan Plasticization

Glycerol is the most widely used plasticizer for the biopolymer chitosan. However, there remains a lack of understanding of the molecular-level interactions between chitosan and glycerol. Here, we describe an in-depth spectroscopic study of the intermolecular interactions between the monomeric repeating unit of chitosan, glucosamine, and the plasticizer glycerol. Infrared and nuclear magnetic resonance spectroscopy were used to probe glucosamine assembly at high and low concentrations to establish diagnostic signals for intra- and intermolecular glucosamine interactions. Systematic addition of glycerol was found to disrupt intramolecular glucosamine hydrogen bonds and promote glucosamine self-assembly. Furthermore, we observed a significant preference for glycerol binding to the amine functionality of glucosamine. These findings indicate that the plasticization of chitosan with glycerol requires a specific binding motif and likely occurs via the gel theory mechanism.

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.

Formulation of anomerization and protonation in d-glucosamine, based on 1H NMR

The major anomer of non-protonated neutral d-glucosamine GlcN⁰ is the β-form, while the α-anomer is dominant for protonated cationic glucosamine GlcNH⁺. The present work confirmed correlation between the anomerization and the protonation by simultaneous determination of signal intensity and chemical shift in pD-variation ¹H NMR, and formulated the equilibrium constants between subspecies α-GlcN⁰, β-GlcN⁰, α-GlcND⁺, and β-GlcND⁺ to interpret the correlation. The individual anomerization constants, K_an = [βGlcN]/[αGlcN] and K_anD = [βGlcND⁺]/[αGlcND⁺], are linked to each other through the relation K_Dα∙K_anD = K_Dβ∙K_an with the deuteration constants K_Dα and K_Dβ of the anomers. The anomer populations are stimulated by OD^- and D⁺ ions in the dose-response form. The acidic deuteron in α-GlcND⁺ is populated mostly at the nitrogen atom, whereas the population in β-GlcND⁺ is comparable at nitrogen and anomeric oxygen; this difference is consistent with the basicity of the nitrogen and the anomerization process of glucosamine.