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

Hang Thi Thuy Le,Hiep Minh Dinh,Lai Thi Nguyen,Phuong Thi Xuan Nguyen,Thu Huynh,Trang Minh Tran

doi:10.32508/stdjns.v2i4.806

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 CO-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.

Highlights

The results showed that the antioxidant properties of these derivatives for OH and ABTS radical scavenging potentials considerably rose compared to non-sulfated EPS-1
The bioactivities were closely related to their physicochemical features, such as molecular weight (M.W.) and sulfate contents, in which antioxidant activity of sulfated derivatives were correlated with increasing sulfate contents, but decreasing M.W. [2, 10]
O. sinensis strain was obtained from Dr Truong Binh Nguyen as a kind gift (Dalat University, Vietnam)

Summary

Introduction

Polysaccharide/exopolysaccharides represented as one of the most prominent compounds of antioxidants, especially the crude expolysaccharides (EPS) isolated from the O. sinensis culture broth [5, 6]. Sinensis culture broth [5, 6] To improve such of activities, sulfation has widely applied to modify the natural polysaccharides [7, 8]. Sulfated modification is an effective method to increase the biological activities of polysaccharides. It enhances the water solubility of polysaccharides due to the presence of polyanionic charges that which leads to increasing of absorption and application as functional foods [2]. Yan et al obtained four sulfated EPS-1 derivatives of C. sinensis fungus by using chlorosulfonic acid (CSA)-pyridine (Pyr) method [2]. The bioactivities were closely related to their physicochemical features, such as molecular weight (M.W.) and sulfate contents, in which antioxidant activity of sulfated derivatives were correlated with increasing sulfate contents, but decreasing M.W. [2, 10]

Objectives

Methods

Results