Asymmetric Reduction of 2-Methyl-2-aryloxyacetic Acids by Glomerella cingulata

The mycotoxin citrinin had antifungal activity under acidic conditions. At the minimum inhibitory concentration, it completely inhibited cellular respiration and partially inhibited the incorporation of radioactive precursors into macromolecules in Saccharomyces cerevisiae. It had no effect on cell permeability. In mitochondrial preparations, it significantly inhibited succinate oxidase and NADH oxidase. Rhizopus chinensis was more sensitive than S. cerevisiae; its growth and mycelial respiration at acidic pH were completely inhibited by lower concentrations of citrinin. The pH-dependent antifungal activity of citrinin seems to be associated with its uptake by fungi. Approximately half of the citrinin taken up was found in mitochondria. The main site of the antifungal action of citrinin, therefore, appears to be the mitochondrial electron transport system.