Study on bath extraction technology of polysaccharide from Hylocereus undatus（Haw.）Britt. et. Rose by ethanol water and evalution on DPPH free radical scavenging ablity of the polysaccharide

The conditions for ethanol water bath extraction of polysaccharide from Hylocereus undatus（Haw.）Britt. et.Rose were optimized by single facfor test and L9 （3^4） orthogonal array design methods. A material-to-liquid ratio of 1：60(g/mL) of 80% ethanol for 20 min extractions performed thrice proved to be the optimal. Using phenol sulfuric acid method and anthrone sulfuric acid method for determination of H. undatus polysaccharide content, the contents of polysaccharide were 19.80% and 20.63%. By comparing the content of polysaccharide from stamens, flower, petal and calyx of H. undatus, we found that flower polysaccharide content was the highest, up to 20.65%. And evaluation of the antioxidant activity of the polysaccharide by DPPH method, EC50 was 5.391 μg/mL.