The modifications of a fructan from Anemarrhena asphodeloides Bunge and their antioxidant activities

Polysaccharide modification exerts important significance for enhancing biological activity. In the present study, a fructan (AAP70-1) extracted from Anemarrhena asphodeloides Bunge was modified by carboxymethylation and sulfation modifications to obtain carboxymethylated derivatives (CM-AAP70-1s) and a sulfated derivative (S-AAP70-1), which were prepared by the chloroacetic acid-isopropanol and the chlorosulfonic acid-pyridine methods, respectively. Physicochemical characteristics and antioxidant activities in vitro of modified derivatives were determined. The results of degree of substitution (DS) and FT-IR analysis indicated that the carboxymethylated and sulfated groups were introduced successfully. After modifications, the DS of CM-AAP70-1s varied from 0.18 to 0.52 and the molecular weights (Mw) were between 4.50 × 10³ and 8.65 × 10³ g/mol. The DS and Mw of S-AAP70-1 were calculated to be 0.61 and 9.76 × 10³ g/mol, respectively. The assays of the antioxidant properties demonstrated that the modified derivatives exhibited stronger scavenging effects toward DPPH and hydroxyl radicals compared with AAP70-1. These results revealed that the chemical modifications could effectively improve the potential of polysaccharides as oxidation inhibitor.