Method for extracting polysaccharide from gynura procumbens

The invention discloses a method for extracting polysaccharide from gynura procumbens. The method comprises the following steps: drying a raw material, namely gynura procumbens; performing primary crushing on the dried gynura procumbens, and further performing superfine crushing so as to obtain a powder material; mixing the powder material with cold water, extracting by using ultrasonic waves in combination with negative pressure cavitation method, and performing centrifugation filtration so as to obtain supernate; filtering the supernate with an ultrafiltration membrane of which the molecularcutoff is 20-30 thousand, collecting a cutoff liquid a, further filtering the cutoff liquid a with an ultrafiltration membrane of which the molecular cutoff is 80-100 thousand, and collecting a cutoff liquid b; and performing vacuum freezing drying on the cutoff liquid b, thereby obtaining a gynura procumbens product. The method is simple in process procedure, that is, can be completed with onlycommon procedures, does no