Antifungal Activity of Essential Oil and Hydrosol Extract of Ballota nigra L. and their Protective Effects Against the Black Rot of Tomatoes

Background: Bellota species are used to treat various diseases in traditional folk medicine. Objectives: This study aimed to chemically characterize the essential oils and the hydrosol extract and regional specificity of the major components of Ballota nigra essential oil and to evaluate their in vitro and in vivo antifungal activities. Methods: Essential oils were obtained by a Clevenger-type apparatus and analyzed by using Gas Chromatography (GC) and Gas Chromatography Mass Spectroscopy (GC/MS). The antifungal activities were tested to three phytopathogenic stains (Penicillium expansum, Aspergillus niger and Alternaria alternata). Results: Altogether, 38 compounds were identified in the essential oils, representing 92.1-96.8% of the total oil composition. Their main constituents were E-β-caryophyllene (4.8-24.6%), E-β-farnesene (3.3-22.9%), β-bisabolene (7.6-30.2%), α-humulene (2.1-13.3%) and geranyl linalool (1.1-8.2%). The statistical methods deployed confirmed that there is a relation between the essential oil compositions and the harvest locations. Hydrosol extract was constituted by seven components, represented principally by methyl eugenol (75.2%) and caryophyllene oxide (12.5%). The results of in vitro antifungal activity with essential oil and hydrosol extract have shown very interesting antifungal activities on Penicillium expansum and Alternaria alternata strains with percentage reductions up to 80%. Additionally, in in vivo assays, Ballota nigra essential oil and hydrosol extract significantly reduce decay in artificially inoculated tomato by Alternaria alternata. Conclusion: The essential oil and hydrosol extract can be used as a potential source of sustainable eco-friendly botanical fungicides to protect stored tomatoes from pathogens, saprophytic fungi causing bio-deterioration to a variety of food commodities.