Preparation of a sulfated exopolysaccharide (S-EPS) from Ophiocordyceps sinensis fungus and its antioxidant effects

Abstract

Sulfated exopolysaccharides have been well-known to enhance biological activities. Exopolysaccharide (EPS) produced by Ophiocordyceps sinensis fungus is a source of natural compounds. The aim of our study is to improve the EPS biological activities by its sulfated modification using the chlorosulfonic acid (CSA)-pyridine (Pyr) method. The appropriate conditions of the sulfation reaction were explored, including CSA/Pyr ratio (v/v) of 1:3 and 6h. The degree of substitution (DS) of S-EPS11 was the highest (DS = 1.59). The total contents of polysaccharides and SO42- of S-EPS11 were 52.25% and 47.15%, respectively. Besides, the FT-IR spectra analysis indicated the presence of C-O-S (peak of 815 cm-1) and S=O (peak of 1129 cm-1) stretching vibrations, while the natural EPS did not appear. Importantly, OH• and ABTS• radical scavenging potential of S-EPS11 significantly increased compared with those of the natural EPS. Together, we successfully generated sulfated EPS extracted from O. sinensis fungus which enhanced antioxidant activities of natural EPS.