Abstract: The fungicidal effects of seven natural isolates were evaluated by flat plate fumigation and block transfer methods. Results showed the fungicidal activity of isolates was in the order of cinnamaldehyde>thymol, salicylaldehyde, citral>anethole>eugenol. However, vanillin did not showed any fungicidal activity. The compound of salicylaldehyde, thymol, citral and cinnamaldehyde, in a ratio of 5:5:5:1, showed significant synergy effect, with the minimum fungicidal concentration (MFC) of 0.031 25 mL/L. SEM analysis showed that the isolate compound made the hypha of Aspergillus flavus become thinner, breakable and wizened, and the spores become shrunken and deformed. The compound affected the normal growth and metabolism of A. flavus, and led to fungistatic or fungicidal activity. The high electron density positions of isolate molecules were the active sites of fungicidal activity. More active sites with higher electron density and smaller steric hindrance resulted in the stronger fungicidal activity. The findings of the present study demonstrated the possible exploration of plants based isolates as safety preservatives against fungal spoilage during food stuffs storage.

Key words: Aspergillus flavus, fungicidal activity, fumigation, isolates