Abstract: The aim of this study was to optimize hot-water extraction conditions of polysaccharides from Sphallerocarpus gracilis. On the basis of single factor test,response surface methodology was applied to optimize the main extraction conditions.The result showed that the optimized conditions were:extraction duration of 5.45 h,extraction temperature of 75 ℃,solid/liquid ratio of 1:34 (g/mL) and with 3 times of extraction.Under these optimized conditions,the extraction yield of polysaccharide was 15.52%.According to the study on DPPH·,·OH and O₂^·- radical scavenging activity,chelating of Fe²⁺ and reducing power, S.gracilis polysaccharide exhibited excellent antioxidant ability.

Key words: Sphallerocarpus gracilis polysaccharide, response surface methodology, chemical structure, antioxidant activity