Characterization of the active compounds of <i>Satureja hortensis</i> L. aerial parts essential oil and its antioxidant, antimicrobial, and anti-biofilm properties against fish pathogenic microorganisms

This study investigated the chemical composition and biological activities of essential oil extracted from the aerial parts of Satureja hortensis (SHEO), with a focus on its antioxidant, antimicrobial, and antibiofilm effects against fish pathogenic strains. SHEO was extracted through Clevenger hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS), which identified carvacrol, γ-terpinene, p-cymene, α-pinene, β-pinene, and α-terpinene as major constituents. The DPPH (IC50: 20.2 μg/mL) and ABTS assays (IC50: 2.6 ± 0.15 μg/mL) revealed considerable antioxidant activity of the essential oil. Antimicrobial properties were tested against several fish pathogenic microorganisms using both disk diffusion and broth microdilution methods. In the agar disk diffusion method, Staphylococcus aureus was found to be the most vulnerable microorganism. SHEO showed broad-spectrum activity, with the lowest MIC values (31.25 μg/mL) observed for S. aureus and Bacillus cereus. Higher MICs were recorded for Escherichia coli, Aeromonas caviae, Candida albicans, and Pseudomonas aeruginosa. SHEO also demonstrated antibiofilm activity in a dose-dependent manner, effectively reducing biofilm formation by P. aeruginosa, S. aureus, and C. albicans. These findings suggest that SHEO may serve as a promising natural agent with antioxidant, antimicrobial, and antibiofilm activities, and could potentially be integrated into sustainable strategies for managing microbial diseases in aquaculture.