Fungitoxic Action of 8-Hydroxyquinoline, Pyridine-N-oxide-2-thiol and Sodium Dialkyl-dithiocarbamates, and their Copper Complexes

Abstract

IN a previous communication¹ on the mode of fungitoxic action on Aspergillus niger, we found that of the copper complexes of 8-hydroxyquinoline (oxine) and pyridine-N-oxide-2-thiol (PTO), the 1 : 2 complexes are toxic, but of the sodium dimethyl-dithiocarbamates (NaDDC) the 1 : 1 complex is toxic but 1 : 2 complex is not. We suggested that this discrepancy is not fundamental but can be explained simply by the difference in solubility of the complexes (Table 1). This hypothesis can now be substantiated by observations on the fungitoxic action on Glomerella cingulata, a more sensitive mould than A. niger. The experiments were carried out as described before¹, in shaken flasks with a basal medium of glass distilled water and analytical grade reagents, the total copper content not exceeding the equivalent of 0.01 p.p.m. CuSO₄.5H₂O. We found that, unlike A. niger, Glomerella cingulata does not show ‘inversion growth’ with sodium dimethyl-dithiocarbamate and copper and, as could be expected on this ground, it is inhibited by copper dimethyldithiocarbamate (CuDDC₂) (Table 1). The toxic concentration of copper dimethyldithiocarbamate appeared to be somewhat higher than the concentration of a saturated solution², but this can be easily understood since the dissolution is a rather slow process. From Table 1 it follows that for all three 1 : 2 complexes G. cingulata is more sensitive than A. niger.