In vitro Fungistatic Action of Phenanthrolines against Pathogenic Fungi

Abstract

WORKING with a diffusion technique described elsewhere¹, I found in August 1948 that a number of phenanthrolines had fungistatic properties, until then unknown. o-Phenanthroline, highly bacteriostatic for Gram-positive and Gram-negative bacteria, has a stronger growth-inhibiting effect against Ctenomyces interdigitalis (=Trichophyton interdigitale) than p- or m-phenanthroline. Alkylation of o-phenanthroline increased its fungistatic action. 2,9-Dimethyl-o-phenanthroline proved to be the most potent fungistatic agent of all phenanthrolines tested. Further alkylation or chlorination of the latter substance resulted in a reduction of its fungistatic action. 2,9-Dimethyl-o-phenanthroline was still effective in the test mentioned above when used in M/1600 solution. The fungistatic properties of this compound were not affected by adding serum to the medium, as happens with a number of fatty acids and their sodium salts. This substance also showed marked bacteriostatic properties against Gram-positive bacteria.