Influence of new fenpropimorph fungicides on the growth and sterol composition in Saccharomyces cerevisiae: Relationship between structure and activity

The toxicity of fenpropimorph and seven newly synthesized analogues against Saccharomyces cerevisiae has been determined in liquid media. The inhibitory effect of the most efficient derivative is 120 times more th an that of standard fenpropimorph. The non-linear relationship between hydr ophobicity and toxicity indicates that the binding of the compounds to the receptors does not differ and so the differences in toxicity reflect change s in the rate of metabolism. The presence of inhibitors in the fermentation medium resulted in a reduction in harvested biomass and Lipid yield, and c hanges in sterol composition-the amount of ergosterol decreased whereas the amounts of lanosterol, dihydroergosterol and squalene increased. The toxicity of the compounds was most influenced by their lipophilicity. U se of this information could lead to development of more potent ergosterol inhibitors.