Effects of the ultra-high pressure on structure and α-glucosidase inhibition of polysaccharide from Astragalus

A novel homogeneous polysaccharide fraction (APS) was extracted from Astragalus by hot water and purified by Sephadex G-100 and G-75 column. Its molecular weight was 693 kDa. APS and APS with ultra-high pressure treatment exhibited significant inhibitory abilities on a-glucosidase, inhibition rate from high to low in order was 400 MPa-APS, 300 MPa-APS, 500 MPa-APS and APS. The inhibition ​percentage of 400 MPa-APS (1.5 mg/mL) was 49% (max.). This suggested that the inhibitory activity of APS on a-glucosidase was improved by ultra-high pressure treatment. FT-IR, SEM, CD spectra, atomic force microscope and Congo red test analysis of APS and 400 MPa-APS showed ultra-high pressure treatment didn't change the preliminary structure but had an effect on its advanced structure.