Preparation method of high-molecular-weight rehmannia polysaccharide and method for steaming fresh rehmannia under high pressure to obtain prepared rehmannia root

The invention discloses a preparation method of high-molecular-weight rehmannia polysaccharide and a method for steaming fresh rehmannia under high pressure to obtain prepared rehmannia root. The preparation method of the prepared rehmannia root comprises the following steps: taking yellow wine as an auxiliary material, and directly steaming fresh rehmannia root at high pressure to obtain the prepared rehmannia root. The preparation method of the high-molecular-weight rehmannia polysaccharide comprises the following steps: (1) performing water extraction on rehmannia to obtain a water extract; (2) carrying out alcohol precipitation on the water extract obtained in the step (1), and collecting the precipitate; and (3) dialyzing the precipitated aqueous solution by adopting a dialysis bag, collecting trapped fluid, and drying to obtain the rehmannia polysaccharide, wherein the molecular weight cutoff of the dialysis bag is 2000 to 50000 Da. According to the high-pressure integrated preparation method of the pre