Antioxidant and antibacterial activities of the essential oils obtained from seven Iranian populations of Rosmarinus officinalis

Rosemary (Rosmarinus officinalis) is an aromatic shrub belonging to the Lamiaceae family and widely used as herbal remedy and spices. In this work, the leaf essential oil from seven populations of rosemary growing in Western Iran was obtained by hydrodistillation and analyzed by GC-FID and GC-MS. The major chemical groups occurring in the essential oils were monoterpene ketones (14.55 to 37.31%), hydrocarbons (28.36 to 36.81%) and oxygen-containing compounds (9.05 to 27.60%). The major constituents of the essential oils were 1,8-cineole (5.63 to 26.89%), camphor (1.66 to 24.82%) and α-pinene (14.69 to 20.81%). The essential oils were screened for antibacterial and antioxidant activities. The antibacterial activity of the essential oils was evaluated on two gram-positive and two gram-negative strains, namely Streptococcus agalactiae, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae by the agar disc diffusion method. Results of antibacterial test indicated that the largest inhibition (inhibition zone of 18.51 mm) was achieved with essential oil from Ma population against E. coli. This sample showed high level of 1,8-cineole. Antioxidant activity of the essential oils was evaluated using the DPPH radical inhibition assay (at 0.4, 0.8, 1.6 and 3.2 mg/ml). Overall, the essential oils from the seven populations, at 3.2 mg/ml, exhibited high antioxidant activity (more than 50% radical inhibition). Statistical analysis revealed a significant correlation between some essential oil components and biological activity displayed.