Essential oil of Thymus vulgaris L. and Rosmarinus officinalis L.: Gas chromatography-mass spectrometry analysis, cytotoxicity and antioxidant properties and antibacterial activities against foodborne pathogens

The essential oil composition of Thymus vulgaris L. and Rosmarinus officinalis L. endemic to France were determined by GC and GC-MS. Oils were assessed for their cytotoxic, antioxidant and antimicrobial activity. 31 and 37 different compounds were identified representing 99.64% and 99.38% of the thyme and rosemary oils respectively, where oxygenated monoterpenes constituted the main chemical class. Thymol (41.33%) and 1.8-cineole (24.10%) were identified as the main constituents of T. vulgaris L. and R. officinalis L., respectively. Essential oils (EOs) of selected plant species were evaluated for their in vitro cytotoxicity against the human lung adenocarcinoma epithelial cell line (A549). Cytotoxicity was measured using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphynyltetrazolium bromide] colorimetric assay. Dose-dependent studies revealed IC50 of 8.50 ± 0.01 μg/mL and 10.50 ± 0.01 μg/mL after 72 h on the A549 cells for R. officinalis L. and T. vulgaris L., respectively. Antioxidant activity was determined using a quantitative DPPH (1,1-diphenyl2-picryl hydrazyl) assay. Thymus and rosemary EOs exhibited effective radical scavenging capacity with 50% inhibitory concentration (IC50) of 437 ± 5.46 μg/mL and 189 ± 2.38 μg/mL respectively and therefore acts as a natural antioxidant agent. The antimicrobial activity of these species has also been studied against several foodborne pathogens and food isolated Salmonella spp. including S. enteritidis of significant importance. According to the results, T. vulgaris L. showed higher bactericidal effect than those from R. officinalis L. These results suggest that the essential oil from T. vulgaris L. and R. officinalis L. have potential to be used as a natural cytotoxic, antioxidant and antimicrobial agent in food processing.