Metabolism and Metabolites of Dithiocarbamates in the Plant Pathogenic Fungus Leptosphaeria maculans

Synthetic compounds containing a dithiocarbamate group are known to have a variety of biological effects and applications including antifungal, herbicidal, and insecticidal application. Leptosphaeria maculans is a fungal pathogen of crucifers able to detoxify efficiently the only plant natural product containing a dithiocarbamate group, the phytoalexin brassinin. To evaluate the effects of dithiocarbamates on L. maculans, a number of structurally diverse S-methyl dithiocarbamates containing indolyl, biphenyl, and benzimidazolyl moieties were synthesized, and their antifungal activities and metabolism by L. maculans were investigated. All dithiocarbamates were transformed by L. maculans through hydrolysis to the corresponding amines, which were less antifungal than the parent compounds. Two dithiocarbonates were shown to be much less antifungal than the corresponding dithiocarbamates. Results of this investigation indicate that S-methyl dithiocarbamates are not useful inhibitors of L. maculans and that their rates of transformation by L. maculans did not correlate with the antifungal activity of the particular compound.