Inhibition of aflatoxin B1 biosynthesis in Aspergillus flavus by anthocyanidins and related flavonoids

Anthocyanidins and precursors or related flavonoids mere tested at concentrations from 0.3 to 9.7 mM (similar to 0.1-3.0 mg/mL) for activity against growth and aflatoxin B-1 biosynthesis by Aspergillus flavus Link:Fr. NRRL 3357. Aflatoxin B-1 production was inhibited by all anthocyanidins tested, and 3-hydroxy compounds were more active than 3-deoxy forms. Monoglycosides of cyanidin were 40% less inhibitory than the aglycon, whereas a monoglucoside and a diglucoside of pelargonidin were 80 and 5%, respectively, as active as the aglycon. Of eight flavonoids tested, only kaempferol was moderately active, whereas luteolin and catechin were weakly inhibitory. Binary combinations of delphinidin and three other aflatoxin inhibitors acted independently of each other. Results with an aflatoxin pathway mutant indicated that anthocyanidin inhibition occurred before norsolorinic acid synthesis.