The invention discloses a method for preparing
astragaloside IV by converting total saponins of
astragalus by microorganisms, which comprises the following steps of: preparing
bacteria, mould and
yeast into bacterium suspension or
spore suspension and inoculating the bacterium suspension or the
spore suspension into a seed culture medium to form seed solution; then inoculating the seed solution into a
fermentation medium to carry out culturing; after the seed solution grows well, adding the total saponins of
astragalus to carry out conversion; carrying out scanning and analysis by a TLC (
Thin Layer Chromatography) to convert other
astragaloside into the
astragaloside IV, so that the amount of the
astragaloside IV is improved by over four times; and extracting the conversion solution by an
organic solvent and separating and purifying the conversion solution by
macroporous resin to obtain a pure product of the
astragaloside IV. According to the method disclosed by the invention, the defects of damage to the saponins, serious
pollution, poor purposiveness and the like in the process of hydrolyzing the total saponins of
astragalus by a chemical method can be overcome and the problem of
enzyme instability in the process of hydrolyzing the total saponins of astragalus by an
enzyme method can be solved. The method has the advantages of no
pollution, strong specificity and high conversion rate. The purity of the prepared
astragaloside IV can reach over 99.9 percent.