Efficient 1H-NMR Quantitation and Investigation of N-Acetyl-D-glucosamine (GlcNAc) and N,N'-Diacetylchitobiose (GlcNAc)2 from Chitin

Abstract

A quantitative determination method of N-acetyl-d-glucosamine (GlcNAc) and N,N′-diacetylchitobiose (GlcNAc)2 is proposed using a proton nuclear magnetic resonance experiment. N-acetyl groups of GlcNAc and (GlcNAc)2 are chosen as target signals, and the deconvolution technique is used to determine the concentration of the corresponding compound. Compared to the HPLC method, 1H-NMR spectroscopy is simple and fast. The method can be used for the analysis of chitin hydrolyzed products with real-time analysis, and for quantifying the content of products using internal standards without calibration curves. This method can be used to quickly evaluate chitinase activity. The temperature dependence of 1H-NMR spectra (VT-NMR) is studied to monitor the chemical shift variation of acetyl peak. The acetyl groups of products are involved in intramolecular H-bonding with the OH group on anomeric sites. The rotation of the acetyl group is closely related to the intramolecular hydrogen bonding pattern, as suggested by the theoretical data (molecular modeling).

Geometrical Structure, Vibrational Spectra and Thermodynamic Properties of Chitosan Constituents by DFT Method

“…These results show that there is a slight increase in C-C separation between two atoms of the rings as the polymer increases in complexity. Similar results were obtained by Liu and co-workers in their investigation of N-Acetyl-D-glucosamine [14]. The important feature in the dimer and trimer molecules is the appearance of the hydrogen bonds O···H-O.…”

Antimicrobial Activity of Chitosan Oligosaccharides with Special Attention to Antiparasitic Potential

“…The 1 H NMR spectrum ( Figure 1A) displayed signals between δH 3.2-4.3 assigned to the H2-6 from GlcN and GlcNAc monomers. Furthermore, the duplet on δH 4.99 (J = 6.3 Hz) was characteristic of the H1α anomeric hydrogen of COSs with β-1-4 glycosidic bonds [36]. The DEPTq-13 C NMR spectrum ( Figure 1B) showed overlapping spectral lines between δC 99.8 and 101.0, characteristic of anomeric carbons and signals between δC 71.0 and 79.0 compatible with oxymethine C3, C4, and C5 carbons from the β-GlcN and β-GlcNAc units, whereas spectra lines with inverted amplitude at δC 59.7-60.0 were assigned to methylene C6 carbons.…”

“…The DEPTq-13 C NMR spectrum ( Figure 1B) showed overlapping spectral lines between δC 99.8 and 101.0, characteristic of anomeric carbons and signals between δC 71.0 and 79.0 compatible with oxymethine C3, C4, and C5 carbons from the β-GlcN and β-GlcNAc units, whereas spectra lines with inverted amplitude at δC 59.7-60.0 were assigned to methylene C6 carbons. This spectrum also permitted the identification of C2-N carbons in δC 56.0 and 55.4 and the methyl carbon from GlcNAc monomers at δC 21.9 [36,37]. The 1 H-1 H-COSY ( Figure 2) revealed sequential connectivity of the hydrogens H1 (δH 4.99) and H2 (δH 3.25), H2 and H3 (δH 4.0), and H5 (δH 4.10) with the diastereotopic hydrogens 2H6 (δH 4.28 and 4.05) from the GlcN units, the majority monomer.…”

Selection of Rhizosphere Bacterial Isolates and Development of Antagonistic Bacterial-Based Formulation to Control Fusarium Wilt on Shallot

“…All bacterial isolates showed the formation of clear zone when cultured on solid medium containing 3% colloidal chitin or glucan. The clear zone was formed after the second day and the longer incubation will widen in diameter until the entire substrate was completely degraded by bacteria or it becomes completely clear (Liu et al 2011). This indicates that the isolates secrete extracellular enzymes (chitinolytic/ glucanolytic).…”