The invention discloses a method for extracting and purifying
polysaccharide from a fermented
mycelium of
Cordyceps sinensis. The method comprises the following steps of: using the fermented
mycelium of
Cordyceps sinensis as a
raw material to produce crude
polysaccharide of the
Cordyceps sinensis via
degreasing, aqueous extraction, concentration and
alcohol precipitation; then, redissolving the crude
polysaccharide into
distilled water, deproteinizing the crude polysaccharide by Sevag, decoloring the deproteinized crude polysaccharide by H2O2, dialyzing the decolored crude polysaccharide, and precipitating the dialyzed crude polysaccharide by
alcohol to produce primarily purified polysaccharide; finally, purifying the primarily purified polysaccharide by
ion-exchange
chromatography, collecting different produced compositions stepwisely, dialyzing the compositions, precipitating the dialyzed compositions by
alcohol,
drying the precipitated compositions to produce the polysaccharide of the Cordyceps sinensis after the precipitated compositions are orderly washed by absolute ethyl alcohol,
acetone, aether and so on. In the produced polysaccharide of the Cordyceps sinensis, MPS2 is identified to be homogeneous polysaccharide by
ultraviolet absorption spectrum and gel
chromatography, with high content of total
sugar. The method has the advantages of simple and convenient extraction steps and low cost.