Antimicrobial and Antioxidant Activities of Rosemary Essential Oil Treated By Gamma Irradiation

The antibacterial and antioxidant activity of the irradiated rosemary essential oil at doses of 0, 5, 10 and 15 kGy were studied. Rosemary essential oil was analyzed by gas chromatography/mass spectrometry (GC/MS). The major components were camphor (20.85%), caryophyllene (18.37%), 1, 8-cineole (14.49%), δ-Cadinene (9.59%) and α-Pinene (8.47%). The antibacterial of the rosemary essential oil as well as the minimum inhibitory dosage (MID) values were recorded. The irradiated rosemary essential oil was generally more effective against bacteria than non-irradiated essential oil. The gram-positive Staphylococcus epidermidis, lactic acid bacteria, Staphylococcus aureus and Bacillus megaterium were more sensitive to non-irradiated and irradiated rosemary essential oil than the gram-negative Escherichia coli, Pseudomonas aeroginosa and Pseudomonas hydrophila. The MID values of tested bacteria to rosemary were in the range of 4-16 μl.ml-1. The in vitro antioxidant activity was investigated with two methods, 2,2-diphenylpicrylhydrazyl radical (DPPH) scavenging assay and tert-butyl hydroquinone (TBHQ) was employed as positive control. The natural essential oil showed antioxidant and DPPH radical scavenging activities and it displayed the inhibition of lipid peroxidation. Then, 0.1% of irradiated rosemary essential oil was added to sunflower oil as natural antioxidant comparing to 0.02% TBHQ as artificial antioxidant. The results showed that irradiation treatment increased the antioxidant activity of rosemary essential oil