Inhibition of aflatoxin biosynthesis by tolnaftate.

Tolnaftate [2-napthyl-N-methyl-N-(m-tolyl)thionocarbamate], an antifungal drug, is widely used to control superficial fungal infections in humans and other animals. In this study the effect of tolnaftate on aflatoxin biosynthesis by Aspergillus parasiticus NRRL 3240 was investigated. Tolnaftate changed the morphology of A. parasiticus to yeastlike forms and inhibited aflatoxin formation. The formation of aflatoxin G was blocked considerably, indicating a metabolic block in the conversion of aflatoxin B to aflatoxin G. The incorporation of [1-14C]acetate into aflatoxin was significantly inhibited at a concentration of 1 mM tolnaftate. The presence of zinc in the resuspension buffer resulted in reversal of the tolnaftate-induced inhibition of aflatoxin G1 biosynthesis.