Effects of Inorganic Salts on Ethanol Precipitation Efficiency and Antioxidant Activity of Sorbus hupehensis Leaves Polysaccharides

In order to improve the alcohol precipitation efficiency of polysaccharides, the effect of adding inorganic salts on the alcohol precipitation efficiency of polysaccharide was investigated. In this study, the effect of inorganic salt type and concentration, alcohol precipitating time and alcohol precipitating volume were investigated by single factor experiments and the three main factors of Na₂SO₄ concentration, alcohol settling time and ethanol volume were optimized by orthogonal experiment. In addition, the infrared spectrum and its antioxidant activity of Sorbus hupehensis leaves polysaccharide were examined. The results showed that when the mass fraction of Na₂SO₄ was 2.0%, ethanol volume was 5 times, ethanol precipitation after 12 h, the yield of polysaccharides was 7.20%±0.12%, while the polysaccharides extracted without inorganic salt was only 2.54%. The infrared spectrum showed that the addition of inorganic salt did not affect the structure of the polysaccharide. In the total antioxidant experiment, the reduction of iron ions was enhanced with the increasing of polysaccharide concentration. When the concentration of polysaccharide was 2 mg/mL, the scavenging rate of DPPH free radical and hydroxyl radical reached 72.87% and 68.39%, respectively, which indicated that the polysaccharide had a certain antioxidant capacity. The above results showed that adding given concentration inorganic salt to the alcohol precipitation had a significant effect on the yield of the polysaccharide, and it could be used as a potential antioxidant in the food.