Combination of Chemically-Characterized Essential Oils from , and : Optimization of a New Complete Antibacterial Formulation Using Simplex-Centroid Mixture Design.

This study aims to identify the volatile profile of three essential oils obtained from (EPEO), (OMEO), and (LBEO) and to examine their combined antibacterial activity that affords the optimal inhibitory ability against and using simplex-centroid mixture design and checkerboard assay. Essential oils (EOs) were isolated by hydrodistillation and characterized using gas chromatography-mass spectrometry (GC-MS) and gas chromatography coupled with flame-ionization detector (GC-FID). The antibacterial activity was performed using disc diffusion and microdilution assays. The chemical analysis revealed that 1,8-cineole (23.75%), p-cymene (22.47%), and -pinene (11.20%) and p-menthane-1,8-diol (18.19%), -pinene (10.81%), and D-germacrene (9.17%) were the main components detected in and EOs, respectively. However, EO was mainly represented by linalool (24.40%) and linalyl acetate (18.68%). The EPEO, LBEO, and OMEO had a strong antibacterial effect on with minimal inhibitory concentrations (MICs) values ranging from 0.25 to 0.5% (v/v). Furthermore, the combination of 1/2048 MIC + 1/4 MIC showed a synergistic antibacterial effect on with a FIC index of 0.25, while the formulation of 1/4 MIC + 1/4 MIC demonstrated an antibacterial synergistic activity on with a FIC index of 0.5. Moreover, the simplex-centroid mixture design reported that the most effective combinations on and correspond to 32%/28%/40% and 35%/30%/35% of , and respectively. Presented information highlights the action of antibacterial formulations of these EOs and suggests their potential applications as alternatives to commercialized drugs to contract the development of bacteria causing serious infections and food deterioration.