Abstract: Houttuynia cordata polysaccharide was prepared by different methods to investigate its anti-EV71,RSV and CV-B3 activities in vitro Polysaccharides were prepared by pepsin hydrolysis,pepsin hydrolysis-Sevag with pH = 4,and pepsin hydrolysis-Sevag with pH = 7.The antiviral effects of polysaccharides and Houttuynia houttuyniae extracts on EV71,RSV and CV-B3 in vitro were investigated by CPE method. Different lyophilized products of Houttuynia cordata—water extract,enzymatic extraction of polysaccharide,enzymatic method-Sevag pH = 7 extraction of polysaccharide,enzymatic method-Sevag pH = 4 extraction yield were 1.87%,1.01%,0.83%,0.88,and the polysaccharide content was 18.21%,22.68%,29.03%,23.07%,respectively.The therapeutic index for EV71 was 24.05,2.73,12.59,6.39 (the therapeutic index of positive drug ribavirin was 43.16),and the therapeutic effect was water extract ≈ extraction of polysaccharides by enzyme-Sevag pH = 7 > extraction rate of polysaccharide by enzyme-Sevag pH = 4 > extraction of polysaccharide by enzyme.The therapeutic indexes of RSV were 2.46,5.43,15.57,9.72 (ribavirin was 19.76)，and the therapeutic effect was extraction of polysaccharides by enzyme-Sevag pH = 7 > extraction rate of polysaccharide by enzyme-Sevag pH = 4 > extraction of polysaccharide by enzyme > water extract.The therapeutic indexes of CV-B3 were 2.81,5.34,17.86 and 5.98 (ribavirin was 18.39),and the therapeutic effect was as follows:extraction of polysaccharides by enzyme-Sevag pH = 7 > Extraction rate of polysaccharide by enzyme-Sevag pH = 4 ≈ extraction of polysaccharide by enzyme > water extract.These results indicated that the polysaccharides prepared from the water extract of Houttuynia cordata and three methods have certain antiviral activity in vitro for EV71,RSV and CV-B3

Key words: Houttuynia cordata, polysaccharide, EV71, RSV, CV-B3