METHOD FOR PREPARING DIHYDROQURCETIN Russian patent published in 2008 - IPC A61K36/15 A61K31/35 C07D311/40 

FIELD: chemical-pharmaceutical industry.

SUBSTANCE: invention relates to an improved method for preparing dihydroquercetin from Siberian or Daurian larch wood. Method for preparing dihydroquercetin involves milling larch wood, thermal treatment of milled larch wood by steam at temperature 110-120^oC, its extraction with extractant followed by separation of extract by filtration, evaporation of extract, distillation off of organic solvent to obtain extract aqueous solution from filtrate, evaporation of aqueous solution to the concentration of dihydroquercetin to be 10%, its acidification with acid to pH 3-3.5, cooling to room temperature and drying at temperature 105-110^oC for 2-3 h. Before first extraction an aqueous condensate formed after thermal treatment of milled larch wood with steam is removed from extraction zone by filtration followed by additional thermal treatment of milled larch wood by steam at temperature 110-120^oC before each change of an extractant. As an extractant method involves using aqueous solution of organic oxygen-containing polar solvent(s) wherein extractant is acidified with acid to pH 5-6. After termination of extraction residues of extractant organic component are distilled off from chips by steam. Method provides increasing yield of dihydroquercetin, reducing volume of used organic solvent and to decrease losses of organic solvent.

EFFECT: improved preparing method.