Chemical Composition of Essential Oils and in vitro Antibacterial Activity of Methanolic Extract of Sonchus arvensis and Eremurus spectabilis against Food-borne Pathogenic Bacteria

Abstract

In this experimental study, chemical composition of essential oils of aerial parts of Sonchus arvensis and roots of Eremurus spectabilis were determined by GC-MS technique. Also antibacterial activity of methanolic extracts of these plants was evaluated on some gram-positive and gram-negative bacteria by disk-diffusion and micro-dilution method to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The bacterial strains included: Bacillus cereus PTCC1015, Staphylococcus aureus PTCC1431, Salmonella enterica PTCC1709 and Escherichia coli PTCC1399. The serial dilutions of the oil were between 3.125 to 400 mg ml-1 prepared in 96 wells microplates using Mueller-Hinton broth for micro-dilution. Results showed thirty-five compounds in the hydro-distilled essential oil from aerial parts of S.arvensis, representing 99.82 % of the total oil. N-Octane (29.82 %) and n-Decane (11.09 %) were the main components. The MIC and MBC varied respectively between 12.5-100 and 100 to >400 mg ml-1 for all gram-positive and gram-negative bacteria. The lowest MIC and MBC observed against S.aureus (12.5 and 100 mg ml-1, respectively). The methanolic extracts of S.arvensis and E.spectabilis also could inhibit the growth of gram-positive and gram-negative bacteria. However, the inhibitory effect was more on gram-positive rather than gram-negative bacteria.