Abstract: We conduct this experiment in order to know the differences of molecular weight of polysaccharides from Jerusalem artichoke with different ethanol precipitation components,as well as inhibition of α-glucosidase and antioxidant activity in vitro.The polysaccharides JAP-1,JAP-2,JAP-3 and JAP-4 with molecular weight of 1959 Da,2180 Da,2746 Da and 2011 Da were obtained by the method of fractional ethanol precipitation,and purified by Sephadex G-50.The inhibitory effects of these components on the activity of α-glucosidase and the scavenging ability of DPPH and hydroxyl radical were measured.The results showed that JAP-4 inhibited the activity of α-glucosidase significantly,and the inhibition rate was 20.32% at 5 mg/mL.At the same time,JAP-1,JAP-2,JAP-3 and JAP-4 all exhibited strong scavenging capacities on DPPH and hydroxyl radicals,the scavenging activity of JAP-2 against DPPH radical and hydroxyl radical was better than other components.The scavenging rate of DPPH radical and hydroxyl radical reached 84.50% and 89.74% at 2 mg/mL,and the scavenging activity was closed to Vc.The activity of polysaccharides with different molecular weights were different,which may be due to the different molecular weights.

Key words: Jerusalem artichoke, polysaccharide, molecular weight, &alpha, -glucosidase inhibitor, antioxidation