Synergistic antioxidant and antibacterial activities of essential oils from Thymus vulgaris, Cinnamomum zeylanicum, and Pistacia atlantica

Essential oils (EOs) are widely recognized as natural preservatives due to their antioxidant and antibacterial properties. Combining multiple EOs may enhance these properties compared to using them singly. Based on this hypothesis, this study aimed to determine the optimal formulation of EOs from Thymus vulgaris , Cinnamomum zeylanicum , and Pistacia atlantica for their antioxidant and antibacterial activities, employing a simplex-centroid mixture design. Antioxidant activity was evaluated using DPPH and FRAP assays. The antibacterial effect against Escherichia coli and Staphylococcus aureus was determined using a disk diffusion assay. Furthermore, the binding interactions of thymol, cinnamaldehyde, and alpha-pinene with bacterial and antioxidant receptor proteins were investigated. The chemical constituents of the EOs were identified through GC-MS analysis. Statistical analysis indicated that a quadratic polynomial model was significant for all responses. ( P < 0.01). The biological activities were reliably predicted through the optimization process. The mixture of EOs showed the highest synergistic effect on antibacterial and antioxidant activity. The optimal formulation, containing 81.927% T. vulgaris , 13.446% P. atlantica , and 4.6265% C. zeylanicum , demonstrated the highest DPPH scavenging activity (89.78%), FRAP activity (11.28 μmol Fe (II)/g), and the largest inhibition zones against E. coli (32.45 mm) and S. aureus (33.53 mm). Molecular docking studies revealed that thymol exhibited strong binding affinities with bacterial target proteins of S. aureus (PDB: 2XCS, 1E93) and E. coli (PDB: 1VLY, 1HN9), as well as antioxidant-related proteins (PDB: 1HD2). Cinnamaldehyde and α-pinene also showed specific interactions with certain proteins. Overall, the results suggest that combining these EOs may provide a promising source of natural antioxidant and antibacterial compounds potentially useful in food and medicine.