Influence of ethephon and soil treatments on the essential oil composition of sweet fennel and its biological activities

The manipulation of cultivation conditions in addition to environmental changes is a key factor affecting the growth, secondary metabolites production, and the biological activity of the plant. Our study aims to evaluate the impact of foliar spray of ethephon, water stress, organic and inorganic fertilizers on the cytotoxic and antimicrobial activities of the fruit oil of Foeniculum vulgare, Miller, var. dulce and its vegetative growth and oil composition. Four different soil treatments were implemented. Gas chromatography coupled with mass spectrometry GC/MS was applied to identify the volatile compounds. Evaluation of both the cytotoxic and the antimicrobial activities of the fruit oil were assessed using the viability assay and the well diffusion method respectively. Variations in the vegetative growth factors and the essential oil (EO) composition were recorded. About a 94.7% increase in the total oil yield was detected in condition 3 compared to control. The oil sample obtained under condition 1 showed the strongest antimicrobial activity against most tested strains and a significant cytotoxic effect against prostate carcinoma (PC-3) cells. Facing the global problem of water deficit, our success in producing a good quality fennel crop and its EO content upon application of drought stress and will be very beneficial at both the economic and the pharmaceutical levels.