INHIBITION OF AFLATOXIN PRODUCTION IN ASPERGILLUS-FLAVUS BY COTTON OVULE EXTRACTS

The effect of cotton ovule extracts on Aspergillus flavus growth and aflatoxin biosynthesis was investigated. Extracts derived from either noninoculated cotton ovule tissue or cotton ovule tissue challenged with A. flavus inhibited aflatoxin (B1) synthesis by fungal cultures of A. flavus. When added to fungal cultures in concentrations of 50-mu-g per mL of medium, extracts derived from fungus-challenged ovule tissue inhibited aflatoxin synthesis by as much as 93%. The ED50 for this type of extract was 18-mu-g per mL of medium (P < 0.01; r2 = 0.46). Similar experiments with a noninoculated ovule extract (50-mu-g/mL medium) produced aflatoxin inhibition levels of up to 77%. The ED50 for noninoculated extracts was 35-mu-g per mL of medium (P < 0.01; r2 = 0.66). These extracts did not inhibit the growth of A. flavus in culture. Cultures of A. flavus that contained pure gossypol (10-50-mu-g/mL medium) also showed significantly reduced levels of aflatoxin production. Gossypol may account for the aflatoxin-inhibitory activity observed in the extracts derived from noninoculated cotton ovule tissue.