Optimization of enzyme-assisted extraction of polysaccharides from alfalfa and its antioxidant activity.

In this present study, an efficient complex enzyme-assisted extraction technology was developed and optimized to extract polysaccharides from alfalfa using four factors at five levels central composite rotatable response surface design (CCRD). The experimental data was fitted to a second order polynomial equation with high coefficient of determination values (R(2)>0.95). The results of statistical analysis showed that the linear and quadratic terms of these four variables had significant effects (P<0.05) on the yield of polysaccharides from alfalfa. The optimum conditions were as follows: enzyme concentration of 2.5%, 2.0%, 3.0% (weight of alfalfa) of cellulase, papain and pectase, extraction temperature 52.7 °C, extraction pH 3.87, ratio of water to raw material 78.92 mL/g and extraction time 2.73 h. Under the optimal conditions, the experimental extraction yield of alfalfa polysaccharides was 5.05 ± 0.02%, which was well matched with the value (5.09%) predicted by the CCRD model. Moreover, evaluation of the antioxidant activity of polysaccharides from alfalfa in vitro suggested that the polysaccharides had good antioxidant effect, especially scavenging activity for hydroxyl radical and DPPH radical, which indicated that the polysaccharides from alfalfa may be explored as a novel natural antioxidant.