Sulfated modification of the polysaccharides from blackcurrant and their antioxidant and α-amylase inhibitory activities.

Sulfated modification was conducted to modify a homogenous polysaccharide from blackcurrant (BCP). The sulfated polysaccharides (SBCPs) with different degree of substitution (DS) were synthesized using the aminosulfonic acid (ASA)/4-dimethylaminopyridine method by varying reaction conditions such as the mass ratio of ASA to BCP, temperature, and time. Three sulfated derivatives were chosen for high-performance gel-permeation chromatography, gas chromatography, fourier-transform infrared (FT-IR) spectroscopy, and nuclear magnetic resonance (NMR), and activity studies, designated as SBCP-1, SBCP-2, and SBCP-3 with DS of 1.28, 0.95, and 0.53, respectively. Results showed that the sulfated modification was successful, and SBCPs had an increase in molecular weight compared to BCP. Both SBCPs and BCP were composed of rhamnose, arabinose, xylose, mannose, galactose, and glucose, with different molar ratios. Sulfate substitution was further confirmed by FT-IR and 13C NMR analysis. SBCPs exhibited excellent antioxidant capacities (DPPH, hydroxyl, and superoxide radical scavenging, reducing power, and ferrous metal-chelating capacities) and α-amylase inhibitory activity in vitro, and the activities of SBCPs were significantly improved in positive correlation with the DS value. This study suggested that SBCPs could serve as potential antioxidant agents to be used as alternative supplements or functional foods.