Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 12 6 2020 12 16 577 583 Mahmoud Osanloo Noncommunicable Diseases Research Center, Fasa University of Medical Sciences, Fasa, Iran AND Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Fasa University of Medical Sciences, Fasa, Iran Ghazal Ghaznavi Department of Medical Biotechnology, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran Abbas Abdollahi Department of Microbiology, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran 2020 07 04 2020 10 20 Background and Objectives: Essential oils (EOs) with different biological activities, such as antibacterial properties, are a valuable resource for developing new drugs. Materials and Methods: Ingredients of six medicinally important EOs, including Artemisia dracunculus, Anethum graveolens, Citrus limon, Citrus sinensis, Cinnamomum zeylanicum and Zingiber officinale, were identified using GC-MS analysis. Moreover, their five major compounds were also listed. Furthermore, the half-maximal inhibitory concentration (IC50) against four important human bacteria was also investigated using the 96-well plate microdilution. Results: C. sinensis EO with IC50 of 1.0 and 4.7 mg.mL-1 have the most effect on the growth of S. aureus and P. aeruginosa. Moreover, EOs of Cinnamomum zeylanicum (IC50: 1.0 mg. mL-1) and Artemisia dracunculus (IC50: 1.3 mg.mL-1) significantly showed better inhibitory effect on E. coli and K. pneumoniae. Conclusion: These EOs could be used for developing inexpensive, potent, and green antibacterial agents. https://ijm.tums.ac.ir/index.php/ijm/article/view/2698 https://ijm.tums.ac.ir/index.php/ijm/article/download/2698/1297