Optimum extraction of acidic polysaccharides from the stems of Ephedra sinica Stapf by Box–Behnken statistical design and its anti-complement activity

The response surface methodology was employed to study the extraction of acidic polysaccharides from the stem of Ephedra sinica Stapf. The quantitative effects of extraction temperature, time, number and ratio of water to raw material on yield of ephedra acidic polysaccharides were investigated with Box–Behnken design. The experimental data were fitted to three second-order polynomial equations using multiple regression analysis and also analyzed using the appropriate statistical methods. By solving the regression equation and analyzing 3-D plots, the optimum condition was at extraction temperature 100 °C, time 3.5 h, numbers 4 and ratio of water to raw material 13.6. Under these conditions, the experimental extraction yield, polysaccharide yield and uronic acid yield were 49.47 mg/g, 33.25 mg/g, and 22.08 mg/g, which were in good agreement with the predicted values. Ephedra acidic polysaccharide exhibited excellent anti-complement activity in vitro, indicating it could be a potential anti-complement therapeutic agent.