Antifungal Activities of Thymol against Aspergillus versicolor on Wheat Grains in the Post-harvest Period: in Silico, in Vitro, and in Vivo Approaches

Aspergillus versicolor (A. versicolor) is a toxigenic fungus species that causes significant post-harvest food spoilage. It is present in several foods, including wheat. The pathogenicity of this species is mainly related to the production of mycotoxins, primarily sterigmatocystin, a carcinogenic toxin that threatens human and animal health. The aim of this work is to conduct in silico, in vitro, and in vivo studies to evaluate the antifungal activity of thymol, a major compound of thyme essential oil (EO), against A. versicolor. Molecular docking of thymol was performed against two fungal proteins, specifically cutinase and chitin synthase. Thymol shows strong interaction with these two target proteins, forming conventional hydrogen bonds. In order to determine the antifungal potential of thymol against A. versicolor in vitro, the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were evaluated in agar medium. The results obtained show a significant antifungal effect of thymol against A. versicolor, with a MIC value of around 0.5 mg/mL and an MFC value double that of the MIC. The MIC concentration causes total inhibition of mycelial growth, resulting in 95% destruction of A. versicolor spores after 24 hours of exposure. Regarding the treatment of grains with thymol, a concentration of 1 mg/mL corresponds to the MFC, causing total inhibition of A. versicolor fungal proliferation and ensuring protection during 8 weeks of storage. A 100% germination rate of wheat grains treated with the MIC concentration thus ensures the agricultural safety of thymol. The results suggest that the antifungal effect of thymol, combined with its safety for wheat, presents a promising alternative for the development of a fungicide for the post-harvest preservation of grains in general, and wheat in particular, against storage fungi. Keywords: Antifungal potential, postharvest fungi, natural compound, grain storage, molecular docking.