Chemical composition and evaluation of antibacterial activity of fennel (Foeniculum vulgare Mill) seed essential oil against some pathogenic bacterial strains

The aim of this work is to assess the in vitro antibacterial activity of the extracted essential oil (EO) obtained from dry seeds of fennel, Foeniculum vulgare Mill, collected from Meknes, (Morocco), against seven pathogenic bacteria: Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus epidermidis and Staphylococcus aureus. The extraction of EO from fennel was performed by hydro-distillation in the Clevenger-type device. The yield was close to 2.82%. The identification of the chemical composition of fennel EO by gas chromatography coupled with mass spectrometry (GC/MS), has given 25 constituents. They represent 97.525% of all constituents existing in the essential oil. The major compound was the trans-anethole (with 44.376%). The result of this study showed that the fennel EO has a remarkable inhibitory activity against the majority of the examined microorganisms, especially against A. baumannii, with the exception of P. aeruginosa and E. coli, as compared to three standard antibiotics. It also exhibited a strong antimicrobial activity against A. baumannii (with a growth inhibition zone of 26 mm) compared to the standard antibiotics examined, with minimum inhibitory concentration (MIC) of 1/2000 (v/v) and S. aureus (growth inhibition zone of 20 mm) with MIC of 1/10000 (v/v). These results indicate that the fennel OE examined represents a potential source of natural antibacterial substances which can be used against pathogenic strains.