Antimicrobial: Antibiofilm, Anti-Quorum Sensing and Cytotoxic Activities of Dorystoechas hastata Boiss & Heldr. ex Bentham Essential Oil

<b>Background/Objectives:</b> The aim of the present study was to evaluate the antimicrobial, antibiofilm, anti-quorum sensing, and cytotoxic activities of the essential oils extracted from the leaves of <i>Dorystoechas hastata</i> Boiss & Helder. ex Bentham (Lamiaceae) (DHL-EO) as well as to determine the chemical composition of the essential oils obtained from both the leaves and roots. <b>Methods:</b> The essential oils of the root and leaf were extracted by the hydrodistillation method. The chemical composition of the two oils was determined by Gas Chromatography-Mass Spectrometry (GC-MS). The antimicrobial activity of DHL-EO was determined against Gram-positive, Gram-negative bacteria, and various <i>Candida</i> species using the broth microdilution method. <i>Pseudomonas aeruginosa</i> PAO1 and <i>Chromobacterium violaceum</i> ATCC 12472 were used for antibiofilm and anti-quorum sensing activities, respectively. The cytotoxic activity of the DHL-EO was examined by MTT assay. <b>Results:</b> Eucalyptol (21.3%), 2-bornanone (17.0%), and α-pinene (10.3%) were the main compounds of the DHL-EO. The root essential oil (DHR-EO) had <i>trans</i>-ferruginol (19.2%), guaiol (14.1%), and <i>ar</i>-abietatriene (14.0%) as the main components. The DHL-EO displayed weak and moderate antimicrobial activity. The DHL-EO showed moderate antibacterial activity against <i>Staphylococcus aureus</i> ATCC 29213 (methicillin-susceptible, MSSA) and <i>S. aureus</i> ATCC 43300 (methicillin-resistant, MRSA), with a MIC value of 12.5 mg/mL. The DHL-EO exhibited the strongest antifungal activity against <i>Candida parapsilosis</i> RSKK 994, with a MIC value of 0.78 mg/mL. It also demonstrated antifungal activity against <i>C. parapsilosis</i> ATCC 22019 and <i>Candida krusei</i> RSKK 3016, with MIC values of 3.12 mg/mL. The DHL-EO showed antibiofilm activity in a concentration-dependent manner, particularly at higher concentrations, and inhibited violacein production in a dose-dependent manner, with anti-quorum sensing activity. The DHL-EO displayed moderate cytotoxic activity against MCF-7 (IC₅₀: 110.3 μg/mL) and A549 (IC₅₀: 120.4 μg/mL) cell lines. <b>Conclusions:</b> The chemical composition of DHL-EO and DHR-EO showed qualitative and quantitative differences from each other in the present study. The essential oil of the leaves showed moderate cytotoxic and antibacterial activities.