Evaluation of antifungal properties of some medicinal plants against Aspergillus flavus isolated from contaminated Corn in vitro

Abstract

Aspergillus strains especially A. flavus and A. parasiticus are the most frequent grains molds producing carcinogenic aflatoxins, which is one of the main challenges in the agriculture and food industries. Chemical pesticides for control of the fungi have adverse effects on human health and environment; therefore, the necessity of finding acceptable substitutes for these substances seem apparent.  In the present study, aqueous extracts of aerial parts of zataria (Zataria multiflora Boiss.), thyme (Thymus vulgaris L.), pennyroyal (Mentha pulegium L.), peppermint (Mentha piperita L.), senna (Cassia senna L.), and basil (Ocimum basilicum L.) along with flowers of safflower (Carthamus tinctorius L.) were examined against A. flavus isolated from contaminated corn.  The extracts with different concentrations (100-600 ppm) and poly ethylene glycol (PEG) with equal osmotic potential of the plant extracts were added to potato dextrose agar (PDA) medium to evaluate fungus growth after 7 days and using agar dilution method.  All concentrations of the extracts significantly inhibited the fungus growth in comparison with each other and the control, while the extracts of thyme and zataria were manifested to be the most effective prohibition with minimum inhibitory concentration (MIC) of 600 ppm. Potency of the plants' extracts on the growth of fungus was evaluated as follows: zataria> thymus> safflower> peppermint> pennyroyal> senna> basil.  Results of this study presented aqueous extracts of thyme and zataria as effective preservatives against growth of A. flavus for corn products.