Optimization of total polysaccharide extraction from Herba Lophatheri using RSM and antioxidant activities. 
Effects of extraction temperature, extraction time and ratio of water to material as well as their interactions on the yield of total polysaccharide from Herba lophatheri were studied by response surface methodology (RSM).  The optimal conditions for the extraction of polysaccharides were determined to be the ratio of liquid to solid of 39.01, extraction time of 2.11h and extraction temperature of 97.09°C.  Under these optimal conditions, the yield of polysaccharides obtained was 5.73±0.10%, which was well matched with the value predicted by the model.  In vitro antioxidant assays showed that the polysaccharides HLP possessed significant inhibitory effects on superoxide radical.  It also exhibited strong 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities, hydroxyl radical scavenging activities and its reducing power, ferrous ions chelating effect was also strong.  These results suggested that H. lophatheri polysaccharides could be a suitable natural antioxidant and may be the functional foods for humans.