Preparation, chemical structure and α-glucosidase inhibitory activity of sulfated polysaccharide from Grifola frondosa
Zehong Chen, Yuxuan Liu, Dan Wang, Niuniu Wu, Kaiping Wang, Yu Zhang
Abstract
Sufalted modification of Grifola frondosa polysaccharide (GFP) was performed using the chlorosulfonic acid-pyridine (CSA-Pyr) method. The chemical structure and α-glucosidase inhibitory activity of sulfated Grifola frondosa polysaccharide (S-GFP) were investigated. FT-IR and NMR spectra both revealed C-6 as the main substituted position owing to steric hindrance. Molecular weight (Mw) analysis indicated that sulfation and degradation could exist concurrently during the sulfation reaction given that the Mw of S-GFP was different from that of natural GFP. Inhibition test of α-glucosidase activity implied that S-GFP is a noncompetitive inhibitor of α-glucosidase. S-GFP effectively inhibited the activity of α-glucosidase with an IC50 value of 3.353 µg mL−1. The results of inhibitory mechanism indicated that S-GFP quenched the endogenous fluorescence of α-glucosidase and changed the backbone structure of the protein. Circular dichroism (CD) analysis showed that treatment with S-GFP changed the conformation of α-glucosidase, increased the content of the α-helix structure, and destroyed the hydrogen bond system of the enzyme. This experiment aims to elucidate the potential α-glucosidase inhibitory activity of sulfated polysaccharides and to provide new insights into the targets of their bioactivities.