Abstract:Foshou yam was used as the raw material for the ultrasound-assisted extraction of polysaccharide via cellulase. The extraction process was optimized through single factor experiments combined with response surface methodology. The structure of the extracted polysaccharide was preliminarily investigated by Fourier transform infrared spectroscopy （FTIR） and ultraviolet spectrophotometry （UV）. Furthermore， the in vitro antioxidant activity of the extracted polysaccharide was evaluated by measuring its total reducing capacity and DPPH and hydroxyl free radical scavenging rates. The results showed that the optimal extraction process was as follows： a solid-to-liquid ratio of 1∶20 （g/mL）， ultrasound time of 20 min， ultrasound power of 450 W， and enzyme addition of 2%. Under these conditions， the extraction rate of polysaccharide from Foshou yam was（33.25±0.48）%. Foshou yam had the polysaccharide content of 91.42%， with very little protein， and there were alpha-pyranose and beta-pyranose in the polysaccharide. In addition， the in vitro antioxidant test results showed that the total reducing capacity and the DPPH and hydroxyl free radical scavenging rates of Foshou yam polysaccharide increased in a concentration-dependent manner. When the polysaccharide concentration was 2.00 mg/mL， the total reducing capacity and the DPPH and hydroxyl free radical scavenging rates peaked， which were 0.459， 77.28%， and 78.58%， respectively. The results showed that the polysaccharide from Foshou yam had high antioxidant activity.