Title : Chemical composition and antifungal activity of the essential oils of Satureja montana and Mentha longifolia
I n the interest of sustainable agriculture and to seek efficient alternatives, growing interest is being shown in developing natural phytosanitary products as an alternative to the tradition use of synthetic chemical products. Here we include essential oils from aromatic plants. Their antioxidant, antifungal, antimicrobial, germination inhibiting properties, etc., have been well-studied, often with very promising results. Those belonging to the genus Satureja stand out with its different types of biological activity, which have been well-described in the bibliography, and data are available that back its potential for antimicrobial, antioxidant and antifungal activity. The objectives pursued in this work were to characterise the chemical composition of S. montana and M. longifolia and study its antifungal activity against fungi, which damage harvests and farming products. Essential oils were identified by gas chromatography with a mass spectroscopy (GC/MS) detector, supplemented with the calculation of Kovats retention indices and some of the main compounds by pure pattern coinjections. Quantification was done with similar GC equipment, but equipped with a flame ionisation detector (FID). The majority compounds were p-cymene (11.6%), ?-terpinene (14.1%) and carvacrol (47.4 %) in summer savory, and piperitone oxide (23.1%) and piperitenone oxide (50.6 %) in M. longifolia. The “in vitro” antifungal activity of essential oils was evaluated following the modified methodology by Singh et al., (2008). Bioassays were run with 100, 200 and 300 μg/mL doses. The antifungal capacity of essential oils was evaluated on phytopathogenic and post-harvest fungi on Alternaria alternata, Botryotinia fuckeliana, Curvularia hawaiiensis, Fusarium equiseti, Fusarium oxysporum lycopersici, Rhizoctonia solani and Verticillium dahliae to obtain a botanical enviro-friendly and low-risk biofungicide. S. montana oil gave excellent results because the 300 μg/mL dose inhibited the growth of all fungi under study, with 100% mycelial growth inhibition (MGI) values for all the fungal species, except for B. fuckeliana, whose MGI value was 92%. The 200 μg/mL dose completely inhibited the growth of four of the seven studied fungal species, while the 100 μg/mL dose maintained antifungal capacity with MGI values ranging from 50-80% on the assayed fungi. The mint essential oil (M. longifolia) also gave satisfactory results for the 300 μg/mL dose, with MGI values between 45% and 60%, 77% on Fusarium oxysporum lycopersici, and a 100% MGI value on Verticillium dahliae. This study evidences the very high potential of the Satureja montana essential oil to control fungi and is a good alternative to agrochemicals.