Use of an antifungal formulation for controlling fungal plant diseases, wherein the phytopathogenic fungi to be controlled include one or more phytopathogenic fungi and wherein the antifungal formulation comprises at least active substances or active substance compositions of polyphenolic extracts, free from anthraquinones and anthraquinone derivatives, of the roots of Rheum species, wherein these active substances or active substance compositions are obtainable by a process comprising the following process steps: a) one-step or multi-step extraction, carried out continuously or batchwise, of the cleaned and comminuted roots, wherein the roots are employed in undried or dried form, by means of an alcoholic solvent; b) gentle removal of the alcoholic solvent under reduced pressure under temperatures of up to not more than 50°C, with the addition of water, wherein, as the result of cooling at a temperature of from 2 to 8°C, lipophilic accompanying substances are precipitated from the aqueous phase formed and are removed by means of filtration or centrifugation and further lipophilic accompanying substances are removed by subsequently extracting the aqueous phase by shaking with petroleum ether or lipophilic accompanying substances are separated from the aqueous phase formed by means of liquid/liquid chromatographic methods; c) exctractive separation of the aqueous extract obtained in b) using an organic solvent from the group of the esters, to give a hydrophilic and a hydrophobic phase; and d) obtaining extracts from both extract phases of process step c) in the following substeps: d 1) a column-chromatographic separation of the hydrophobic extract phase or of the hydrophilic extract phase on Sephadex LH-20 is carried out, wherein the eluents employed in succession are different alcohols and a mixture of solvents of the alcanone series and water, and thereafter d 2) those fractions obtained from the hydrophobic phase or the hydrophilic phase which have in each case the same constituent spectrum are combined to give active substance fractions, whereupon d 3) a selection of individual active substance fractions for use is made after performing a proof of activity of the active substance fractions in respect of their protective and/or curative activity against phytopathogenic fungi. a) one-step or multi-step extraction, carried out continuously or batchwise, of the cleaned and comminuted roots, wherein the roots are employed in undried or dried form, by means of an alcoholic solvent; b) gentle removal of the alcoholic solvent under reduced pressure under temperatures of up to not more than 50°C, with the addition of water, wherein, as the result of cooling at a temperature of from 2 to 8°C, lipophilic accompanying substances are precipitated from the aqueous phase formed and are removed by means of filtration or centrifugation and further lipophilic accompanying substances are removed by subsequently extracting the aqueous phase by shaking with petroleum ether or lipophilic accompanying substances are separated from the aqueous phase formed by means of liquid/liquid chromatographic methods; c) exctractive separation of the aqueous extract obtained in b) using an organic solvent from the group of the esters, to give a hydrophilic and a hydrophobic phase; and d) obtaining extracts from both extract phases of process step c) in the following substeps: d 1) a column-chromatographic separation of the hydrophobic extract phase or of the hydrophilic extract phase on Sephadex LH-20 is carried out, wherein the eluents employed in succession are different alcohols and a mixture of solvents of the alcanone series and water, and thereafter d 2) those fractions obtained from the hydrophobic phase or the hydrophilic phase which have in each case the same constituent spectrum are combined to give active substance fractions, whereupon d 3) a selection of individual active substance fractions for use is made after performing a proof of activity of the active substance fractions in respect of their protective and/or curative activity against phytopathogenic fungi. d 1) a column-chromatographic separation of the hydrophobic extract phase or of the hydrophilic extract phase on Sephadex LH-20 is carried out, wherein the eluents employed in succession are different alcohols and a mixture of solvents of the alcanone series and water, and thereafter d 2) those fractions obtained from the hydrophobic phase or the hydrophilic phase which have in each case the same constituent spectrum are combined to give active substance fractions, whereupon d 3) a selection of individual active substance fractions for use is made after performing a proof of activity of the active substance fractions in respect of their protective and/or curative activity against phytopathogenic fungi.