Factors Influencing the Fungistatic Action of 8-Hydroxyquinoline (Oxine) and Its Metal Complexes

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Abstract
The fungistatic effect of oxine against Aspergillus niger is greatly reduced if the medium is first freed of Cu++ and toxicity increases with increasing amts. of Cu. The toxicity is overcome by lowering the pH of the medium even in the presence of quite large amts. of Cu. Removal of Fe++ slightly reduces the fungistatic activity of oxine but deficiencies of Zn, Mn, or Mo have no effect. Oxine inhibition is not reversed by the addition of high concns. of Co, Zn, Mn, Fe, or Cu and only partially by Mo. The toxicity of 7 chelators was tested in the presence and absence of Cu and, of these, 4 showed an increase in fungistatic action in the presence of Cu. These findings are discussed in relation to the possible mode of action of oxine and its metal complexes on fungal cells.