Characterization and bioactivity of water-soluble polysaccharides from the fruit of pumpkin

Four fractions of water-soluble polysaccharide, coded as PP1, PP2, PP3 and PP4, were isolated and purified from the fruit of pumpkin at 20°C, 40°C, 60°C and 80°C, respectively. Their chemical structure and physico-chemical properties were characterized by FT-IR spectra, gas chromatography and viscometry, respectively. Furthermore, their antioxidant activities were evaluated in vitro. The results indicated that four fractions of pumpkin polysaccharide were all composed of L-arabinose (Ara), L-rhamnose (Rha), D-glucose (Glu), D-galactose (Gal) and D-glucuronic acid, with variation of the component ratio. The polysaccharides showed polyelectrolyte effect due to the existing of glucuronic acid. PP1 showed the highest scavenging rate on hydroxyl radicals and superoxide radicals among four fractions of pumpkin polysaccharide. The four polysaccharide fractions were found to have the ability to alleviate the liver mitochondria swelling at concentration 2 mg/ml. The scavenging rate on lipid peroxidation in liver homogenate by anti-oxidation of PP1, PP2, PP3 and PP4 were 64.09%, 55.3%, 35.4% and 49.9% at concentration 2.5 mg/ml, respectively.