The invention relates to the field of
pharmacy, and discloses a
Bletilla striata
polysaccharide extract and a preparation method thereof. The preparation method comprises the following steps: crushingand sieving a
Bletilla striata medicinal material to prepare
Bletilla striata
powder; adding the
Bletilla striata powder to water, and carrying out ultrasonic extraction, centrifuging and filtering to prepare
Bletilla striata water extract; concentrating the
Bletilla striata water extract, adding
ethanol to precipitate, taking the obtained precipitate, and washing and
drying the precipitate to obtain crude Bletilla striata polysaccharides; and adding
distilled water to dissolve the crude Bletilla striata polysaccharides, centrifuging the obtained solution, taking the obtained supernatant, sequentially carrying out
microfiltration and
ultrafiltration, concentrating the filtered supernatant, precipitating the obtained concentrate with
alcohol, and taking, washing and
drying the obtained precipitate in order to obtain the Bletilla striata
polysaccharide extract. The ultrasonic extraction process used to destroy
cell walls of the Bletilla striata
powder facilitates the full dissolving ofthe Bletilla striata polysaccharides, and
microfiltration-
ultrafiltration combined purification is carried out based on the preparation of the crude Bletilla striata polysaccharides through an ultrasonic
water extraction and
alcohol precipitation technology to prepare the Bletilla striata
polysaccharide extract, so the method can effectively remove proteins,
starch and other impurities, and the prepared Bletilla striata polysaccharide extract has a high purity and a
low protein content, and is free from
starch and inactive polysaccharides.