Chemical composition, antibacterial activity and mechanism of action of essential oil from seeds of fennel (Foeniculum vulgare Mill.)

Fennel (Foeniculum vulgare Mill.) is widely cultivated and used as a culinary spice. In this work, the chemical composition of the essential oil obtained by hydrodistillation of fennel seeds was analyzed by gas chromatography-mass spectrometry (GC-MS), and 28 components were identified. Trans-anethole (68.53%) and estragole (10.42%) were found to be the major components. The antibacterial activity, minimum inhibitory concentration (MIC), and minimum bactericide concentration (MBC) of essential oil against several food-borne pathogens were evaluated. The results showed that the gram positive and gram negative strains of bacteria had different sensitivities to essential oil of fennel seeds, the essential oil exhibited antibacterial activity against Staphylococcus albus, Bacillus subtilis, Salmonella typhimurium, Shigella dysenteriae and Escherichia coli according to the results of MIC and MBC. Among these bacteria, S. dysenteriae was the most sensitive to essential oil, showing the lowest MIC and MBC values of 0.125 and 0.25 mg/mL respectively. In addition, kill-time assay also showed that the essential oil had a significant effect on the growth rate of surviving S. dysenteriae. We concluded that the mechanism of action of the essential oil against S. dysenteriae might be described as essential oil acting on membrane integrity according to the results of the leakage of electrolytes, the losses of contents (proteins, reducing sugars and 260 nm absorbing materials) assays and electron microscopy observation.