Shahrekord University of Medical Sciences Future Natural Products 2783-4662 5 1 2019 06 30 Phytochemical composition and antibacterial properties of the essential oil of Achillea biebersteinii Afan. (Asteraceae) 41 48 EN Asad Kazemi Faranak Elmi Journal Article 2019 02 04 2019 06 24 Background and aims: The aim of this study was to characterize the chemical composition and antimicrobial properties of Achillea biebersteinii essential oil (EO). Methods: The chemical composition of samples obtained from Marand city in East Azerbaijan, was assessed using gas chromatography mass spectrometry (GC/MS). The antimicrobial properties were evaluated by the disc diffusion method against methicillin-resistant Staphylococcus aureus (MRSA), other extended-spectrum beta-lactamases (ESBLs) producing, as well as Gram-negative and Gram-positive bacteria. The minimum inhibitory concentration (MIC) value of EO was assessed using the agar dilution method. Results: In A. biebersteinii the major compounds were α-terpinene (41.42%), 2-carene (13.96%), m-cymene (13.41%) and 1,8-cineole(8.91%).The EO showed antimicrobial activity against ten microorganisms, especially Streptococcus sanguis, S. aureus (MRSA strain), and Klebsiella pneumoniae (ESBL-producing strain), which was potentially better than tetracycline and kanamycin. Conclusion: This study confirmed that EO of A. biebersteinii has in vitro antimicrobial activity against Gram-negative and Gram-positive bacteria, which has made it an alternative antibacterial agent.