Effect of phosphorylation on antioxidant activities of pumpkin (Cucurbita pepo, Lady godiva) polysaccharide

Abstract Phosphorylated derivatives of pumpkin polysaccharide with different degree of substitution were synthesized using POCl 3 and pyridine. Antioxidant activities and cytoprotective effects of unmodified polysaccharide and phosphorylated derivatives were investigated employing various in vitro systems. Results showed that high ratio of POCl 3 /pyridine could increase the degree of substitution and no remarkable degradation occurred in the phosphorylation process. Characteristic absorption of phosphorylation appeared both in the IR and 31 P NMR spectrum. The d f values between 2.27 and 2.55 indicated the relatively expanded conformation of the phosphorylated derivatives. All the phosphorylated polysaccharides exhibited higher antioxidant activities. H 2 O 2 -induced oxidative damages on rat thymic lymphocyte were also prevented by the derivatives. In general, phosphorylation could improve the antioxidant activities of pumpkin polysaccharide both in vitro and in a cell system.