Optimization of the Antibacterial Activity of a Three-Component Essential Oil Mixture from Moroccan Thymus satureioides, Lavandula angustifolia, and Origanum majorana Using a Simplex-Centroid Design.

Background/objectives: The rise of antibiotic-resistant pathogens has become a global health crisis, necessitating the development of alternative antimicrobial strategies. This study aimed to optimize the antibacterial effects of essential oils (EOs) from Thymus satureioides, Lavandula angustifolia, and Origanum majorana, enhancing their efficacy through optimized mixtures.

Methods: This study utilized a simplex-centroid design to optimize the mixture ratios of EOs for maximal antibacterial and antioxidant effectiveness. The chemical profiles of the EOs were analyzed using gas chromatography-mass spectrometry (GC-MS). The antibacterial activity was assessed against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa using minimum inhibitory concentration (MIC) tests, while antioxidant activity was evaluated through DPPH (2,2-diphenyl-1-picrylhydrazyl), and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assays.

Results: The optimized essential oil mixtures demonstrated potent antibacterial activity, with MIC values of 0.097% (v/v) for E. coli, 0.058% (v/v) for S. aureus, and 0.250% (v/v) for P. aeruginosa. The mixture ratios achieving these results included 76% T. satureioides, and 24% O. majorana for E. coli, and varying proportions for other strains. Additionally, L. angustifolia essential oil exhibited the strongest antioxidant activity, with IC₅₀ values of 84.36 µg/mL (DPPH), and 139.61 µg/mL (ABTS), surpassing both the other EOs and standard antioxidants like BHT and ascorbic acid in the ABTS assay.

Conclusions: The study successfully demonstrates that optimized mixtures of EOs can serve as effective natural antibacterial agents. The findings highlight a novel approach to enhance the applications of essential oils, suggesting their potential use in food preservation and biopharmaceutical formulations. This optimization strategy offers a promising avenue to combat antibiotic resistance and enhance food safety using natural products.