Use of an antifungal formulation for the treatment of fungal plant diseases, where the phytopathogenic fungi that are fought belong to one or more phytopathogenic fungi and the antifungal formulation contains at least active substances or active substance compositions of polyphenolic extracts of type- roots. Rheum, without any anthraquinone or anthraquinone derivatives, where these active substances or active substance compositions are available through a method, which includes the following steps: a) continuous or discontinuous extraction carried out in mono- or polyphasic form of purified roots and divided, where non-dried or dried roots are used, by means of an alcoholic solvent； b) careful removal of the alcoholic solvent with reduced pressure and with temperatures up to a maximum of 50 ° C by adding water, where lipophilic complementary substances precipitate from the aqueous phase formed by cooling at a temperature of 2 to 8 ° C and are removed by filtration or centrifugation and other lipophilic complementary substances are removed by subsequent stirring of the aqueous phase with petroleum ethers or lipophilic complementary substances are separated from the aqueous phase by means of a fluid / chromatographic fluid method； c) extractable separation of b) extract obtained by applying an organic solvent from the group of esters in a hydrophilic phase and a hydrophobic； and d) obtaining extracts of both phases of extract from the step of the process c) in the following partial stages: d1) a column chromatographic separation is performed in Sephadex LH-20 of the hydrophobic extract phase or the hydrophilic extract phase, where as elution medium various alcohols are used one after the other and a mixture of solvents of the alkanone series and water, and then d2) the fractions obtained from the hydrophobic phase or the hydrophilic phase with the same spectrum of components respectively correspond to fractions of substance active, to which d3) a selection of individu
