Optimization of extraction conditions and investigation of antioxidant activity of polysaccharides from purple yam

The polysaccharide extraction from purple yam was optimized based on single factor experiment combined with orthogonal design.The optimum extraction conditions were achieved when the ratio of solid to liquid was 1∶15( mg / m L) at 55 ℃ for 2 h.Under such conditions,the yield ratio of purple yam polysaccharide reached as high as 2.58% ± 0.03%. The antioxidant activity of crude polysaccharide from purple yam was extensively investigated by antioxidant experiments tests based on DPPH,superoxide radical,ABTS and EDTA. The experimental results showed that the polysaccharides from purple yam exhibited significant antioxidant activity in the DPPH and ABTS tests with free radical scavenging rates being 66.24% at 2 mg / m L and 69.50% at 24 mg / m L,respectively,which was better than the polysaccharides from Yam.