Chemical modification and antioxidant activity of the polysaccharide from Acanthopanax leucorrhizus

A water-soluble polysaccharide (ALP) from Acanthopanax leucorrhizus was chemically modified to obtain two sulfated derivatives (S-ALP1 and S-ALP2), two phosphorylated derivatives (P-ALP1 and P-ALP2) and two acetylated derivatives (A-ALP1 and A-ALP2) with different degree of substitution (DS). Their structures were characterized by chemical and spectral (IR, 13C NMR and 31P NMR) analysis, and in vitro antioxidant activity were evaluated by reducing power assay, DPPH• and HO• scavenging assay. The results obtained showed that the modifications were successful, although the molecular weight (Mw) of the ALP derivatives decreased due to slight degradation during the reaction. Physicochemical and antioxidant properties of ALP changed by the chemical modifications, and the type of the substitution group and DS played a decisive role in the antioxidant activity of the derivatives. P-ALP and S-ALP with higher DS displayed stronger antioxidant abilities on scavenging DPPH• and HO•, ferric-reducing power compared with ALP, and exhibited a certain dose-effect relationship, whereas A-ALP were less effective. These results provide a scientific basis for the further studies and utilization of A. leucorrhizus polysaccharides.