Antioxidant and antibacterial activities of Thymus numidicus and Salvia officinalis essential oils alone or in combination

Abstract

Combinations between antibiotics and other antimicrobial substances such as plant essential oils represent one of the most promising advances against drug-resistant microorganisms. The aim of this study was to evaluate, by the microdilution method, the antibacterial effects of different combinations of two essential oils with their major components or antibiotics (cephalosporines) against Staphylococcus aureus, Escherichia coli, Serratia marcescens, Klebsiella pneumoniae, Pseudomonas aeruginosa and the antioxidant effect of the same essential oils combined with thymol or DL-α-tocopherol against DPPH free radical. Two aromatic plants widely growing in north Algeria, Thymus numidicus (Poiret) and Salvia officinalis (Linné), were investigated. Essential oils were extracted from these plants through hydrodistillation method. Extraction yields were evaluated at 1.83% for T. numidicus (Poiret) and 0.97% for S. officinalis L. Synergistic interaction was observed with DL-α-tocopherol-T. numidicus essential oil tested against DPPH free radical. Additional effect was noted with ciprofloxacine-T. numidicus essential oil combination tested against S. aureus. However no significant action was observed among the other combinations used in this study for the investigation of antibacterial or antioxidant activities.