Abstract

Essential oil extracted from the aerial parts of Rosmarinus officinalis by hydrodistillation was analyzed by gas chromatography/mass spectrometry and the components identified were 15. The major constituents of the essential oil were 1,8-cineole (35.32%), trans-caryophyllene (14.47%), borneol (9.37%), camphor (8.97%), α-pinene (7.9%) and α-thujone (6.42%). R. officinalis essential oil was screened for its in vitro antioxidant activities using three different and complementary assays: 1,1-diphenyl-2-picrylhydrazyl (DPPH), β-carotene bleaching test and reducing power. The results of the DPPH assay showed an IC₅₀ inhibitory concentration of 110.20 μg/ml. In the β-carotene bleaching test, the IC₅₀ value was 20.00 μg/ml. At a higher concentration (70 μg/ml), this essential oil exhibited a lower reducing power with an absorbance value of 0.72 ± 0.02. The corresponding value EC₅₀ was evaluated as 38.68 μg/ml. Comparison of the antioxidant properties of the investigated essential oil with those expressed by BHT (used as a positive control), showed that this oil exhibited a slightly weak antioxidant potential than BHT and therefore acts as a natural antioxidant agent. 

Key words:  Rosmarinus officinalis, chemical composition, essential oil, antioxidant activity.