Investigations of organic fungicides. VIII. The biochemical mode of action of bisdithiocarbamates and diisothiocyanates

The inhibitory action of tetramethylene diisothiocyanate (TMDI) and of disodium ethylene bisdithiocarbamate (nabam) on the spore germination of Penicillium italicum and of Aspergillus niger is strongly antagonized by the thiol compounds, thioglycollic acid and cysteine. This antagonism is supposed to be due to a chemical reaction between fungicide and -SH compound. The observation that the preformed reaction products of either of the fungicides with thioglycollic acid are almost non-toxic is strong evidence for this hypothesis. The observed reactivity of thiol compounds towards TMDI and nabam is an indication that the antifungal action of the latter compounds is due to their combination with cell constituents carrying essential -SH groups. In a final section the mode of antifungal action of the bisdithiocarbamates and related compounds is discussed more generally