Essential Oil of Rosmarinus officinalis L.: Phytochemical Composition, Antioxidant and Antibacterial Activity Against Multidrug-Resistant Strains Isolated from Cucumbers

The cucumber (Cucumis sativus L.) is eaten raw or lightly processed, which makes it a potential vehicle for foodborne bacteria; the spread of resistant strains has renewed interest in plant-derived control agents. This work characterized the phytochemical profile of Rosmarinus officinalis essential oil (REO) and assessed its antioxidant capacity and its antibacterial activity against multidrug-resistant (MDR) strains of Escherichia coli and Staphylococcus aureus isolated from cucumber fruits. REO was obtained by steam distillation in a Clevenger-type apparatus (yield 1.3%). Gas chromatography coupled with mass spectrometry (GC-MS) identified 21 compounds, among which α-pinene (32.53%), 1,8-cineole (20.73%), and verbenone (6.80%) predominated. Antioxidant activity was 49.60 ± 0.69 µM TE/mL REO for the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical and 13.15 ± 0.51 µM TE/mL REO for the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, with IC50 values of 24.46 ± 2.11 and 56.43 ± 1.86 mg/mL, respectively. The minimum inhibitory concentration (MIC) ranged from 0.19 to 3.12 mg/mL and the minimum bactericidal concentration (MBC) from 0.39 to 6.25 mg/mL. These results highlight REO’s in vitro bactericidal potential and support its evaluation as a component of disinfectant formulations or edible coatings for cucumber.