Preparation, chemical structure and α-glucosidase inhibitory activity of sulfated polysaccharide from Grifola frondosa

Abstract

• Sulfated Grifola frondosa polysaccharide was prepared and characterized. • Sulfation and degradation could exist concurrently during the sulfation reaction. • S-GFP is a noncompetitive inhibitor of α-glucosidase. • S-GFP could significantly quench the endogenous fluorescence of α-glucosidase. 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 IC 50 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.