Synergistic antimicrobial activity of essential oils mixture of Moringa oleifera, Cinnamomum verum and Nigella sativa against Staphylococcus aureus using L-optimal mixture design.

The urgent need to address the growing problem of antimicrobial resistance in multidrug-resistant bacteria requires the development of pioneering approaches to treatment. The present study aims to evaluate the antimicrobial potential of the essential oils (EOs) of Moringa oleifera (moringa), Cinnamomum verum (cinnamon), and Nigella sativa (black seed) and the synergistic effect of the mixture of these oils against Staphylococcus aureus MCC 1351. Statistical modeling revealed cinnamon oil had the highest individual antimicrobial potency, followed by black seed oil. The combination of the three EOs exhibited significant synergistic effects compared to the individual oils, with a Fractional Inhibitory Concentration (∑FIC) index of 0.27. L-Optimal mixture design of response surface methodology (RSM) identified the optimal mixture as moringa: cinnamon: black seed oils by the ratio of (1:1:1) in run 15 (0.338:0.307:0.355 mL) (v/v). This mixture exhibited significant antibacterial efficacy, outperforming individual oils and conventional antibiotics like tetracycline. Specifically, the combination reduced the MIC values from 3.12, 0.78, and 6.25 to 0.25, 0.06, and 0.78 μg/mL for moringa, cinnamon, and black seed oil, respectively. Synergistic interactions between oils further boosted efficacy, with moringa-cinnamon and cinnamon-black seed pairings exhibiting the strongest synergies. The developed predictive models for IZD and MIC showed excellent fit, with R