Application of Simplex-Centroid Design Methodologies to Optimize the Anti-bacterial and Anti-candidal Activity of the Mixture of Mentha pulegium, Pituranthos chloranthus and Thymus algeriensis Essential Oils

Abstract

This work aims to study the antimicrobial activities of the essential oils of M. pulegium, P. chloranthus and T. algeriensis and to identify the antagonistic or synergistic impacts of their combinations. Antimicrobial activities were analyzed by disc diffusion and microdilution against six foodborne microbial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and Candida albicans). That's why, to predicate the optimal mix, we are using the Augmented Simplex Centroid Design. The chemical composition shows that the main compound of M. pulegium were pulegone (50.31%) and menthone (26.92%). For P. chloranthus EO, The major constituents were dillapiole (13.56%) and pregnane (8.47%) and the main products of T. algeriensis EO are Camphor (14.06%), β-Phellandrene (13.71%) and α-pinene (8.55%). The antimicrobial activity of the three studied EOs confirms the highest antibacterial activity of T. algeriensis and P. chloranthus EO against a lower antibacterial activity of M. pulegium EO. Moreover, the response surface analysis showed significant synergistic effects in some binary and ternary mixtures. The optimal mixture predicted against C. albicans corresponded to 12%, 35% and 53% of M. pulegium, P. chloranthus and T. algeriensis EOs, respectively. While the optimal mixture predicted against S. aureus was composed by P. chloranthus and T. algeriensis essential oils at 84% and 16%, respectively. Similarly, this binary mixture, between P. chloranthus and T. algeriensis, presented optimal antimicrobial activity against P. aeruginosa composed by essential oils at 20% and 80%, respectively. Generally, the combination between 19% M. pulegium, 41% P. chloranthus and 40% T. algeriensis consisting the optimal ternary mixture Eos. Our findings show that by the use of mixture design we can predict antibacterial interaction of essential oils. Therefore, it can be used as a natural antimicrobial agent and a food additives.