Plant-based natural flavonoids show strong inhibition of aflatoxin production and related gene expressions correlated with chemical structure

Aflatoxins are strong carcinogenic and mutagenic fungal metabolites, and aflatoxin contamination is a critical issue in agriculture and food production. Natural flavonoids can suppress aflatoxin biosynthesis; however, the structure-activity relationship remains unclear. In the present study, a total of 36 structurally related natural flavonoids were tested against the aflatoxigenic Aspergillus flavus, both in-vitro and in-situ (on maize kernels), to investigate their structure-activity relationship and biological activity. Aflatoxin production (IC50 values: 10.85-20.09 μg/mL) and the expression of related genes (aflD, aflK, aflQ, and aflR) were found to be strongly inhibited. Structure-activity relationship studies revealed that the [-OH] or [-O-CH3] groups at position 6 of ring A and position 4' of ring B were closely associated with antifungal and antiaflatoxigenic activities. These findings provide valuable information for the development of clean and safe methods to prevent aflatoxin contamination in food.