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

Abstract

Essential oils (EO) of <i>Origanum compactum</i> Benth. (<i>O. compactum</i>) 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 <i>O. compactum</i> 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 <i>Candida albicans (C. albicans), Aspergillus flavus (A. flavus), Aspergillus niger (A. nige)</i>, and <i>Fusarium oxysporum (F. oxysporum)</i>. Repellent potential and toxicity of EO by contact and inhalation were tested against <i>Callosobruchus maculatus</i> (<i>C. maculatus</i>). The yield of essential oil obtained by hydrodistillation of <i>O. compactum</i> 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 <i>A. niger</i> and <i>C. albicans</i> even at the lowest MIC values (3.125 μg/mL). Concerning insecticidal activity, the EO caused total mortality of <i>C. maculatus</i> adults at a dose of 20 μL/L air with LC₅₀ 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 <i>O. Compactum</i> EO could be a sustainable and environmentally friendly alternative bioinsecticide and bio-fungicide to replace the chemically synthesized forms.