Optimization of antifungal activity of essential oils and in-silico computational evaluation on AA7 oxidoreductase

Abstract

Several studies have demonstrated the potential of essential oils as natural antimicrobial agents. However, few publications focus on combinations of essential oils and optimizing the concentration to reduce the minimum inhibitory concentration. The present study aimed to investigate the combined antifungal activity of three essential oils extracted from Moroccan Origanum compactum, Thymus leptobotrys and Laurus nobilis and to predict the optimal combination using the mixture design approach coupled with the microdilution test against the phytopathogenic fungal species Alternaria alternata. The individual antifungal activity of essential oils demonstrated that Origanum compactum essential oil is the most effective (MIC=0.065% (v/v)). Through the optimization of essential oils formulations, a synergistic effect was identified, enabling the modeling and validation of the data and the establishment of a predictive profile. The optimal mixture was determined to be a blend of 40% Oregano, 46% Thyme, and 14% Laurel. To identify effective biofungicides, we performed in-silico molecular docking analysis targeting the vital enzyme, AA7 oxidoreductase, from the fungus Alternaria alternata, which regulates the metabolism of pectin degradation products, using some of the main natural compounds found in studied essential oils. Virtual screening revealed that the compounds exhibited favorable binding energy with the target protein. Analysis of the SwissADME server indicated that the metabolites possess fungicidal properties, making them effective and environmentally and biologically safe fungicides. These results are important for developing biological control methods to protect olive cultivation against Alternaria alternata leaf diseases.