CHEMICAL AND ANTIMICROBIAL INVESTIGATIONS ON ESSENTIAL OIL OF ROSMARINUS OFFICINALIS LEAVES GROWN IN ETHIOPIA AND COMPARISON WITH OTHER COUNTRIES
This study has been concerned with determining the chemical composition and antimicrobial activity of essential oil extracted from R. officinalis leaves grown in Ethiopia. The essential oil was obtained by hydrodistillation and yielded clear and intense yellow brownish 1.1% (w/w) oil with pleasant smell. The oil was analyzed by GC/MS and resulted in the identification of 43 compounds, representing 100% of the total oil. The major components of R. officinalis oil were 1, 8-cineole (23.55%), verbenone (18.89%), camphor (15.06%), α-terpineol (6.43%), isoborneol (5.68%), tridecyl acrylate (5.57%), linalool (3.71%), bornyl acetate (3.57%), trans-caryophyllene (3.36%), terpine-4-ol (2.78%) and α-pinene (1.40%). In vitro antimicrobial activities of the essential oil of R. officinalis was determined by paper disk diffusion method and showed moderate antimicrobial activity in both 10 and 20 μL concentrations. Escherichia coli and Staphylococcus aureus were used as test bacterial strain where as Apergillus niger and Fusarium oxysporum were selected as test fungi. The presence of monoterpene and oxygenated monoterpene as the major constituents of the essential oil could be responsible for the moderate antimicrobial activity in this study. The results of this study showed some differences in the antimicrobial activities and chemical composition of the essential oil when compared with similar studies conducted in other countries.