2-isopropyl-5-methylphenol isolated from Ruta graveolens and its structural analogs show antibacterial activity against food-borne bacteria

The antimicrobial activities of the essential oil obtained from the aerial parts of Ruta graveolens and 2-isopropyl-5-methylphenol analogs were evaluated against six food-borne bacteria. The essential oil of R. graveolens aerial parts exhibited potent antimicrobial activity against six food-borne bacteria. 2-Isopropyl-5-methylphenol was isolated by chromatographic analyses. The structure-activity relationships of the 2-isopropyl-5-methylphenol analogs, 2-isopropyl-5-methylphenol, and its structural analogs (2-isopropylphenol, 2-methylphenol, phenol, and 2-isopropyl-5-methylbenzene) were determined against six food-borne bacteria. When employing the agar diffusion method, 2-isopropyl-5-methylphenol and 2-isopropylphenol had potent antimicrobial activities against the six food-borne bacteria. The minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) values of 2-isopropyl-5-methylphenol and its structural analogs were determined against the six food-borne bacteria. 2-Isopropyl-5-methylphenol exhibited the strongest activity (MIC, 5–6.25 μg/mL; MBC, 6.25–12.5 μg/mL) against the six food-borne bacteria. Therefore, the essential oil of R. graveolens and 2-isopropyl-5-methylphenol analogs should be useful as natural food preservatives.