From sustainable harvesting to antibacterial activity: Yield optimisation, chemical composition, and foodborne pathogen inhibition of Juniperus communis L. and Pistacia lentiscus L. essential oils
Abstract
The present study evaluated the chemical composition and antibacterial activity of Juniperus communis L. and Pistacia lentiscus L. essential oils and their 50:50 mixture against clinically relevant Gram-positive and Gram-negative bacteria. Antibacterial activity was assessed using agar diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and fractional inhibitory concentration index (FICI) assays, while chemical profiles were characterised by gas chromatography-mass spectrometry (GC-MS) and FTIR (Fourier-transform infrared spectroscopy) analyses. Both essential oils exhibited antibacterial activity, with Gram-positive bacteria showing greater susceptibility than Gram-negative strains. The MBC/MIC ratios were ≤ 4 for all tested samples, indicating a predominantly bactericidal effect. Among the evaluated formulations, the 50:50 mixture displayed the highest antibacterial activity, particularly against Staphylococcus aureus ATCC 6538, with a MIC value of 6.25% (v/v) and a synergistic interaction against S. aureus (FICI = 0.49). GC–MS analysis showed that the mixture was predominantly composed of monoterpene hydrocarbons (71.42%), followed by sesquiterpene hydrocarbons (14.71%), oxygenated monoterpenes (7.11%), and oxygenated sesquiterpenes (1.14%). The major constituents identified were α-pinene, limonene, β-pinene, myrcene, and terpinen-4-ol. FTIR analysis confirmed the terpene-rich nature of the oils and supported the GC-MS results. The enhanced antibacterial activity of the mixture is likely associated with additive and synergistic interactions among its bioactive compounds, leading to increased disruption of bacterial cellular functions. These findings suggest that the combination of J. communis and P. lentiscus essential oils represents a promising natural antibacterial agent, particularly against Gram-positive pathogens.