The fungicide cymoxanil impairs respiration in Saccharomyces cerevisiae via cytochrome c oxidase inhibition.

Cymoxanil (CYM) is a widely used synthetic acetamide fungicide, but its biochemical mode of action remains elusive. Since CYM inhibits cell growth, biomass production, and respiration in Saccharomyces cerevisiae, we used this model to characterize the effect of CYM on mitochondria. We found it inhibits oxygen consumption in both whole cells and isolated mitochondria, specifically inhibiting cytochrome c oxidase (CcO) activity during oxidative phosphorylation. Based on molecular docking, we propose that CYM blocks the interaction of cytochrome c with CcO, hampering electron transfer and inhibiting CcO catalytic activity. Although other targets cannot be excluded, our data offer valuable insights into the mode of action of CYM that will be instrumental in driving informed management of the use of this fungicide.

Development and Validation of an Analytical Method for Volatiles with Endogenous Production in Putrefaction and Submersion Situations.

A group of 16 volatile substances (ethyl acetate, 2-propanol, 1-propanol, methanol, acetone, ethanol, acetaldehyde, diethyl ether, methyl ethyl ketone, 1-butanol, 2-butanol, t-butanol, isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 1-pentanol) were qualitatively and quantitatively analyzed through a method developed for volatiles with endogenous production in putrefaction and submersion situations. The method was validated for blood, urine and vitreous humor, using a gas chromatograph (Varian 450-GC) with a flame ionization detector coupled to a headspace injector (HS-GC-FID). The vials were prepared by diluting 100 µL of the sample of interest in 1 mL of internal standard (acetonitrile 100 mg/L), using two capillary columns (VF-624ms and VF-5ms) with different polarities to ensure that all test compounds would be properly identified and undoubtedly distinguished from the rest. All volatiles were studied in a range of 50 to 2,000 mg/L in terms of selectivity/specificity, detection and quantification limits, linearity and calibration model, precision, accuracy, bias, robustness and stability according to the Scientific Working Group for Forensic Toxicology. Detection and quantification limits were between 1 to 8 mg/L and 4 to 24 mg/L, respectively, with coefficient of variation values under 10% in bias studies and in intermediate precision studies for most substances. The developed method was applied to real cases to test the method.