Abstract: In order to optimize the ultrasonic-assisted enzymatic extraction process of polysaccharide from Cedrus deodara pine needles,and investigate the structure of polysaccharide and its antioxidant activity.The optimal extraction parameters were determined by response surface methodology as follows:3.0 g pine needle powder,liquid to material ratio 20∶1 (mL∶g),extraction temperature 80 ℃,ultrasonic power 560 W,ultrasonic extraction time 47 min with the amount of cellulase 12 FPU/g raw material,and extraction twice,the polysaccharide yield was as high as 10.39%.The structure of pine needle polysaccharide was characterized by high performance liquid chromatography,infrared spectroscopy and nuclear magnetic resonance spectroscopy.The purified polysaccharide,linked mainly by β-glycosidic bonds,consisted of monosaccharides such as glucose,fructose,arabinose and galactose.Antioxidant activities of the polysaccharides were evaluated on the basis of hydroxyl radical (·OH) and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·).The scavenging ability of the crude polysaccharide was much higher than that of purified polysaccharide,which showed a good dose-effect relationship.The semi-inhibitory concentrations IC₅₀ of the crude polysaccharide on ·OH and DPPH· were 0.47 g/L and 0.076 g/L,respectively.

Key words: Cedrus deodara pine needles, polysaccharide, ultrasonic-assisted enzymatic extraction, response surface methodology, characterization;antioxidant activity