This research shows that essential oil from cinnamon leaves can effectively prevent a dangerous fungus (Aspergillus flavus) from contaminating stored foods like peanuts and grains, and stops it from producing a cancer-causing toxin called aflatoxin. The oil works by damaging the fungus’s cell membrane, disrupting its energy production, and triggering stress responses. Ten main aromatic compounds in the oil, especially eucalyptol and borneol, are responsible for this protective effect. This suggests cinnamon leaf oil could be used as a natural, safe alternative to chemical fungicides for protecting stored food.