Investigation of Chemical Composition, Antibacterial and Antioxidant Activity of Thymus daenensis and Thymus eriocalyx Essential Oils against Human Pathogenic Bacteria

Introduction: Plant essential oils can be used as alternative agents for the treatment of antibiotic-resistant pathogenic bacteria. This study aimed to investigate the chemical composition, antibacterial, and antioxidant activity of Thymus eriocalyx and Thymus daenensis essential oils against Gram-positive and Gram-negative human pathogenic bacteria. Methods: The aerial part of Thymus eriocalyx and Thymus daenensis in the full flowering stage were collected from West Azerbaijan Province (Urmia), Iran, in ۲۰۱۴. We obtained the essential oils using a Clevenger device. The disc diffusion method was used to determine the antibacterial activity of the essential oils against ۱۵ Gram-positive and Gram-negative PTCC and ATCC bacterial standards. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were measured by microdilution broth method in ۹۶-well plate and free radical scavenging activity by ۲,۲-diphenyl-۱-picrylhydrazyl. Chemical analysis of the essential oils performed out by gas chromatography connected to Mass spectrometry. Results: Eleven (۹۴.۰۶%) and seven (۹۰.۷۶%) compounds were identified in T. eriocalyx and T. daenensis essential oils, respectively. The major components of T. eriocalyx essential oil were thymol (۳۷.۸%) and α-terpineol (۱۴.۹۱%), and of T. daenensis were thymol (۵۲.۳۶%) and carvacrol (۱۶.۷۲%). T. eriocalyx essential oil showed the highest activity against B. cereus with MIC of ۰.۹۳ μg mL- and MBC of ۱.۸۷ μg mL-. The most potent radical scavenging activity was also obtained for T. daenensis essential oil. Conclusion:  Essential oil components of T. eriocalyx and T. daenensis may have the potential to be used as antimicrobial agents against antibiotic-resistant pathogenic bacteria.

Keywords:

Essential oil , Antibacterial , Chemical composition , Pathogenic bacteria , Thymus spp