Abstract: The polysaccharide from blackcurrant fruit obtained by microwave-assisted solvent extraction was degraded by the Fe2+-VC-H2O2 method under ultrasonic assistance, and purified by Sepharose 6B column chromatography inton two fractions (DP-1 and DP-2). The results of liquid chromatography showed that the molecular masses of DP-1 and DP-2 were 1.29 × 106 and 1.07 × 106 Da, respectively. Gas chromatography indicated that both polysaccharides were composed of six monosaccharides but with different molar ratios. Fourier transform infrared (FTIR) spectroscopy, periodate oxidation and nuclear magnetic resonance (NMR) spectroscopy proved the existence of α- and β-pyranose rings in the chains of both polysaccharides and that each was mainly composed of six sugar residues. The functional characterization showed that DP-1 and DP-2 had definite moisture absorption and retention abilities and thermal stability. The two polysaccharides had significant inhibitory activity on α-glucosidase and α-amylase with maximum inhibition percentages of (67.45 ± 3.45)% and (73.22 ± 0.48)% for α-glucosidase, and (64.74 ± 2.08)% and (73.28 ± 2.52)% for α-amylase being observed at a concentration of 2.0 mg/mL respectively. Besides, the inhibitory effects of the two polysaccharides on α-amylase were reversible and competitive. Therefore, this study may provide a theoretical basis for further utilization of polysaccharides from blackcurrant fruit.

Key words: blackcurrant; degraded polysaccharide; structure characteristics; moisture absorption and moisture retention capacity; hypoglycemic activity