Mode of action of pesticides on aflatoxin biosynthesis and oxidase system activity

Area of Science:

• Mycology
• Food Science
• Toxicology

Background:

• Aflatoxins are toxic secondary metabolites produced by Aspergillus species.
• Pesticide use can potentially influence fungal metabolism and toxin production.
• Understanding these interactions is crucial for food safety and agricultural practices.

Purpose of the Study:

• To investigate the effects of nine different pesticides on aflatoxin biosynthesis.
• To examine the impact of these pesticides on oxidase activity in Aspergillus flavus and mutant strains.
• To determine which pesticide classes and specific compounds inhibit or alter aflatoxin production pathways.

Main Methods:

• Tested nine pesticides against wild-type Aspergillus flavus and mutant strains (A. parasiticus avr-1, A. parasiticus ver-1).
• Quantified aflatoxin (B1, B2, G1, G2) and anthraquinone (versicolorin A, versiconal hemiacetal acetate, averufin) biosynthesis.
• Assessed oxidase enzyme activity involved in aflatoxin production.

Main Results:

• Different pesticide classes exhibited varied effects on aflatoxin and anthraquinone accumulation.
• Phosphonic, phosphorothioic, phosphorodithioic, and phosphoric acid derivatives showed differential inhibition of aflatoxins and accumulation of intermediates.
• Phenylurea derivatives (linuron, pencycuron) inhibited all aflatoxins, while iprodione completely blocked the pathway in mutant strains.
• Oxidase activity was linked to averufin and versicolorin A conversion; profenfos and iprodione inhibited enzymes in this pathway.

Conclusions:

• Pesticides have diverse impacts on aflatoxin biosynthesis pathways in Aspergillus.
• Specific pesticide chemistries, like iprodione and profenfos, can significantly disrupt aflatoxin production.
• Further research is needed to understand the mechanisms and implications of these interactions for food safety.