Abstract: Through single factor and orthogonal experiment,the effect of solid-liquid ratio,ultrasonic temperature,ultrasonic power and ultrasonic action time on the extraction of cowherb seed polysaccharide were studied.UV spectrophotometry and pyrogallol autoxidation method were used to determine the effect of cowherb seed polysaccharide on scavenging DPPH·and O₂^-·. According to the result of these tests,the antioxidant activity in vitro of cowherb seed polysaccharide was evaluated. The optimum ultrasonic extraction conditions were as follows:solid-liquid ratio(g:mL) 1:50,ultrasonic temperature 60 ℃,ultrasonic power 100 W and ultrasonic action time 40 min.Under these conditions,the extraction rate of the cowherb seed polysaccharide was 9.60%.Preferable ultrasound extraction process of cowherb seed polysaccharide was time-saving,highly efficient,reliable and reproducible.The antioxidant test in vitro indicated that cowherb seed polysaccharide n had strong ability of scavenging on DPPH·and O₂^-·, and its antioxidative effect and concentration showed good dose-effect relationship in a certain range.

Key words: cowherb seed, orthogonal design, ultrasonic extraction, polysaccharides, antioxidation