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International Journal of Spectroscopy
Volume 2014, Article ID 789356, 6 pages
http://dx.doi.org/10.1155/2014/789356
Research Article

Structural Characterization of Amadori Rearrangement Product of Glucosylated Nα-Acetyl-Lysine by Nuclear Magnetic Resonance Spectroscopy

1College of Chemical and Environmental Engineering, Chongqing Three Gorges University, Chongqing 404100, China
2Agriculture and Agri-Food Canada, 6000 C&E Trail, Lacombe Research Centre, Lacombe, AB, Canada T4L 1W1
3Department of Chemistry, The University of Hong Kong, Pokfulam Road, Pokfulam, Hong Kong

Received 20 November 2013; Revised 11 February 2014; Accepted 17 February 2014; Published 17 April 2014

Academic Editor: Guang Zhu

Copyright © 2014 Chuanjiang Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Maillard reaction is a nonenzymatic reaction between reducing sugars and free amino acid moieties, which is known as one of the most important modifications in food science. It is essential to characterize the structure of Amadori rearrangement products (ARPs) formed in the early stage of Maillard reaction. In the present study, the Nα-acetyl-lysine-glucose model had been successfully set up to produce ARP, Nα-acetyl-lysine-glucose. After HPLC purification, ARP had been identified by ESI-MS with intense [M+H]+ ion at 351 m/z and the purity of ARP was confirmed to be over 90% by the relative intensity of [M+H]+ ion. Further structural characterization of the ARP was accomplished by using nuclear magnetic resonance (NMR) spectroscopy, including 1D 1H NMR and 13C NMR, the distortionless enhancement by polarization transfer (DEPT-135) and 2D 1H-1H and 13C-1H correlation spectroscopy (COSY) and 2D nuclear overhauser enhancement spectroscopy (NOESY). The complexity of 1D 1H NMR and 13C NMR was observed due to the presence of isomers in glucose moiety of ARP. However, DEPT-135 and 2D NMR techniques provided more structural information to assign the 1H and 13C resonances of ARP. 2D NOESY had successfully confirmed the glycosylated site between 10-N in Nα-acetyl-lysine and 7′-C in glucose.