Comprehensive In Vitro and In Silico Analysis of Antimicrobial and Insecticidal Properties of Essential Oil of Myrtus communis L. from Algeria

This study investigated the phytochemical composition and biological activities of <i>Myrtus communis</i> essential oil (EO) from Algeria, focusing on its antimicrobial, antifungal, and insecticidal properties using in vitro and in silico approaches. Gas chromatography-mass spectrometry (GC-MS) analysis identified myrtenyl acetate (57.58%), 1,8-cineole (17.82%), and α-terpineol (6.82%) as the major constituents. <i>M. communis</i> EO exhibited significant antibacterial activity, particularly against <i>Staphylococcus aureus</i> (13.00 ± 0.70 mm) and <i>Salmonella typhimurium</i> (13.00 ± 1.50 mm), with moderate inhibition of <i>Bacillus subtilis</i> (10 ± 1.00 mm) and <i>Escherichia coli</i> (9.00 ± 0.70 mm), while <i>Pseudomonas aeruginosa</i> showed resistance. The antifungal activity was notable against <i>Fusarium oxysporum</i> (16.50 ± 0.50 mm), <i>Aspergillus fumigatus</i> (11.00 ± 1.00 mm), and <i>Penicillium</i> sp. (9.00 ± 0.60 mm) but ineffective against <i>Aspergillus niger</i>. Insecticidal activity against <i>Tribolium castaneum</i> was evaluated using contact toxicity, fumigation toxicity, and repellent activity assays. The EO demonstrated potent insecticidal effects, with an LC₅₀ value of 0.029 µL/insect for contact toxicity and 162.85 µL/L air for fumigation after 96 h. Additionally, the EO exhibited strong repellent activity, achieving 99.44% repellency at a concentration of 0.23 mg/cm² after 24 h. Density functional theory (DFT) calculations provided insights into the molecular geometry and electronic properties of the key bioactive compounds. Molecular docking studies evaluated their binding affinities to bacterial enzymes (<i>DNA gyrase</i>, <i>dihydrofolate reductase6</i>, and <i>Gyrase B</i>) and insecticidal targets (<i>acetylcholinesterase</i>), revealing strong interactions, particularly for geranyl acetate and methyleugenol. These findings highlight <i>M. communis</i> EO as a promising natural antimicrobial and insecticidal agent, with potential applications in plant protection and biopesticide development.