Chemical composition of selected aromatic plant essential oils and their antifungal efficacy against toxigenic fungi associated with maize (Zea mays L)

Essential oils (EOs) are volatile compounds that can serve as alternatives to chemical pesticides for the management of plant pests, including fungal pathogens. The current study was carried out to investigate the chemical composition and antifungal activities of EO extracted from three plants, Thymus vulgaris, Coriandrum sativum and Cymbopogon martini, grown in southwestern Ethiopia. EOs were extracted from the leaves of each plant by hydro distillation using a Clevenger apparatus. The chemical composition of the oils was analyzed by Gas chromatograph-Mass Spectrometry (GC-MS), and their inhibitory effects were tested against mycotoxigenic fungi isolated from maize kernels belonging to Aspergillus and Fusarium. Chemical analysis revealed the presence of 32 compounds in C. sativum with hexanedioic acid, bis (2-ethylhexyl) ester (46.9%) and 2-Decenal (E)-(12.6%) being the dominant compounds. T. vulgaris contained 25 compounds, of which thymol (34.4%) and o-cymene (17.5%) were the major components. Twenty-five compounds were detected in C. martinii of which geraniol (51.4%) and geranyl acetate (14.5%) were dominant. The EOs of the tested plants had very high antifungal activity (up to 100% efficacy) against Aspergillus flavus, A. niger, Fusarium graminearum and F. verticillioides in vitro and on maize grains. The anti-fungal activities of these EOs were dependent on their major components, including thymol, hexanedioic acid, bis (2-ethylhexyl) ester and geraniol. This study confirmed the potential of EOs as bio-fungicides for the management of mycotoxigenic fungi associated with maize. This could reduce the health impacts of mold and toxigenic compounds produced in maize in a sustainable and environmentally friendly manner.