Chemical Composition and Antifungal, Insecticidal and Repellent Activity of Essential Oils From Origanum compactum Benth. Used in the Mediterranean Diet

Essential oils (EO) of Origanum compactum Benth. (O. compactum) are well known for their biological and pharmacological activities. This study aimed to assess the chemical composition, antifungal, insecticidal and repellent activities of EO of O. compactum used in the Mediterranean diet. Phytochemical screening was conducted using gas chromatography-mass spectrometry (GC/MS). Antifungal activity was tested by the disc diffusion method followed by a minimal inhibitory concentration (MIC) assay against Candida albicans (C. albicans), Aspergillus flavus (A. flavus), Aspergillus niger (A. nige), and Fusarium oxysporum (F. oxysporum). Repellent potential and toxicity of EO by contact and inhalation were tested against Callosobruchus maculatus (C. maculatus). The yield of essential oil obtained by hydrodistillation of O. compactum was 4.41 ± 0.35%, mainly composed of Carvacrol (38%) and Thymol (31.46%). Regarding antifungal activity, the results revealed a wide antifungal spectrum of the studied EO against the tested strains, which reached 100% growth inhibition, especially against A. niger and C. albicans even at the lowest MIC values (3.125 μg/mL). Concerning insecticidal activity, the EO caused total mortality of C. maculatus adults at a dose of 20 μL/L air with LC(50) value of 5.3 μL/L air. A significant reduction in the number of eggs and emergence was proportionally recorded with increasing doses up to 100% at 20 μL/L air. For repellent activity, the studied EO showed a moderate repellent activity with an average percentage of 39.16%. The outcome of this work revealed that O. Compactum EO could be a sustainable and environmentally friendly alternative bioinsecticide and bio-fungicide to replace the chemically synthesized forms.