Abstract:This paper explored the relationship between the antioxidant activity of pumpkin polysaccharides and its molecular weight and monosaccharides composition，and provided a new reference for the study of the relationship between pumpkin polysaccharide.Pumpkin polysaccharide was extracted by ultrasonic assisted extraction with gourd pumpkin as raw material.After the decolorization of Sevag method and AB-8 macroporous adsorption resin，the decolorized pumpkin polysaccharides （Cucurbita moschata Duch polysaccharide，CMP）was obtained，5 kinds of pumpkin homogeneous polysaccharides named CMP-A1、CMP-A2、CMP-B、CMP-C1 and CMP-D2 were isolated and purified by cellulose DEAE Cellulose-52 and Sephadex G-100 chromatography column.The molecular weight and monosaccharide composition were determined respectively，and the relationship between them and the antioxidant activity of 5 kinds of homogeneous polysaccharides was investigated.The results were as follows：compared with CMP-B，the molecular weight of CMP-C1 and CMP-B was similar.The glucuronic acid content of CMP-C1 was significantly higher than that of CMP-B.The scavenging rates of DPPH·and·OH free radicals by CMP-C1 were 10.21%and 11.03%higher than that of CMP-B，respectively.Compared with CMP-B，the content of uronic acid in CMP-D2 and CMP-B was basically the same.The molecular weight of CMP-D2 was significantly less than that of CMP-B，but the scavenging rates of DPPH·and·OH free radicals by CMP-D2 were only 1.05%and 1.96%higher than that of CMP-B，respectively.The content of uronic acid in pumpkin homogeneous polysaccharide had a great influence on its antioxidant activity.The antioxidant activity increased with the increase of glucuronic acid content.and the smaller the influence of molecular weight on its antioxidant activity.