Process optimization and antioxidant activity of polysaccharide from Actaea cimicifuga L. residue extracted by alkaline method

【Objective】The extraction process of polysaccharide from Actaea cimicifuga L. residue was optimized by alkaline method，and antioxidant capacity of the polysaccharide was investigated，which provided reference for comprehensive development and utilization of A. cimicifuga L. residue.【Method】Using the water extracted and alcohol precipitated A. cimicifuga L. residue as the experimental material，the polysaccharide from the A. cimicifuga L. residue was extracted by alkaline extraction method. The effects of lye concentration,liquid-material ratio,extraction temperature and extraction time on the extraction rate of polysaccharide were investigated. The optimal single factor conditions were screened and the response surface model was established. The antioxidant capacity of polysaccharide was investigated by in vitro free radical scavenging test.【Result】With the extraction rate（Y）of alkaline extracted polysaccharide from A. cimicifuga L. residue as the response value，the quadratic polynomial fitting equation established with lye concentration （A），liquid-material ratio（B）and extraction temperature（C）as independent variables was Y=4.98+0.17A+0.27B+ 0.72C-0.34AB+0.21AC-0.073BC-0.76A²-0.33B²-0.79C². The model obtained from the study was stable and well-fitted. The order of influencing factors on polysaccharide extraction rate was extraction temperature > liquid-material ratio > lye extraction concentration. Lye extraction concentration had significant effects（P<0.05，the same below），liquid-material ratio and extraction temperature had extremely significant effects（P<0.01，the same below），interaction between lye concentration and liquid-material ratio had extremely significant effects，the interaction between lye concentration and extraction temperature had significant effects. However，the interaction between liquid-material ratio and extraction temperature had no significant effect（P>0.05）. Through response surface analysis，the optimal technological conditions for extracting polysaccharide from A. cimicifuga L. residue by alkali extraction were obtained：the concentration of lye was 0.6 mol/L，the liquid-material ratio was 27∶1，and the extraction temperature was 75 ℃，and the average extraction rate of polysaccharide was 5.17%. The median inhibition concentratin（IC₅₀）values of polysaccharides from A. cimicifuga L. residue on 1,1-diphenyl-2-trinitrophenylhydrazine（DPPH）free radicals，hydroxyl free radicals and 2,2-azino-bis（3-ethylbenzothiazoline-6-sulfonic acid）（ABTS）free radicals were 2.614，1.164 and 1.306 mg/mL. When polysaccharide concentration was 1.2 mg/mL，the clearance rates were 45.83%，56.16% and 45.12% respectively.【Conclusion】This method can extract polysaccharide from A. cimicifuga L. residue efficiently，and the polysaccharide from A. cimicifuga L. residue has antioxidant activity in vitro，and its antioxidant activity has dose dependent relationship with concentration.