Structural characterization and antioxidant activity of a heteropolysaccharide isolated from Hedysarum polybotrys

Abstract

A water-soluble polysaccharide (HPS3aS) with a molecular mass of 1.22 × 10⁴ Da was isolated from Hedysarum polybotrys using anion-exchange and gel-permeation chromatography. HPS3aS exhibits a globular-shaped conformation in 0.1 M NaNO₃ by size exclusion chromatography with multi-angle laser light scattering (SEC-MALLS). The investigation of the structural features of this heteropolysaccharide through a combination of chemical and instrumental analyses revealed that the backbone of HPS3aS is composed of α-d-(1 → 4)-linked glucopyranose residues, which occasionally branched at O-6. The branches are composed of (1 → 4)-linked galactopyranose residues and terminated with glucopyranose residues. HPS3aS possesses good in vitro antioxidant activity, as evaluated by scavenging assays with 1,1-diphenyl-2-picrylhydrazyl, hydroxyl, and superoxide radicals, which suggests that HPS3aS could be a potential antioxidant.

Keywords::

• Hedysarum polybotrys
• polysaccharide
• structure feature
• antioxidant activity

Acknowledgments

This study was financed by a grant from Science and Technology Program of Gansu Province (No.1304FKCA101). The authors are grateful to Professor Wei Zhou, for providing instrumental facilities of GC–MS, Gansu Entry-Exit Inspection and Quarantine Bureau. The authors are also grateful to College of Chemistry and Chemical Engineering of Lanzhou University for the NMR spectra and elemental analysis.