Extraction and scavenging free radical effects of polysaccharides from Gastrodia elata

Response surface methodology（RSM）was applied to optimize the extraction conditions for polysaccharides from Gastrodia elata based on single factor tests. Technological condition parameters were determined according to regression analysis. The optimum conditions were as follows：ratio of water to material was 40：1，ultrasonic power output was 75.70%，extraction time was 29.32 min. Spectrophotometry and chemiluminescence were employed to compare the abilities of scavenging free radicals including DPPH·，O2 -·，·OH，H2O2 and ONOO- of polysaccharides extracted from G. elata and three natural antioxidants α-lipoic acid，Vc and VE. The results showed that at the concentration of 0-500 μg/mL，the scavenging ability of polysaccharides extracted from G. elata on DPPH· was similar to that of α-lipoic acid，stronger than that of VE，obviously weaker than that of Vc，the highest clearance rate reached 12.23%；the scavenging ability on ·OH was weaker than that of Vc，similar to that of α-lipoic acid and VE at the concentration of 400-500 μg/mL，the highest clearance rate reached 4.85%；the scavenging ability on H2O2 was stronger than that of α-lipoic acid，slightly weaker than that of VE，obviously weaker than that of Vc，the highest clearance rate reached 25.80%；the scavenging ability on ONOO- was obviously weaker than that of Vc and α-lipoic acid，the highest clearance rate reached 20.52%.