Chemical composition and antimicrobial effects of essential oils of ten Eucalyptus species against Micrococcus loteus and Escherichia coli

Essential oils in aromatic plants are one of the valuable classes of natural product with medicinal properties. Many species from the genus of Eucalyptus contain essential oils and these oils could be used because of their antimicrobial effects. In this research, the essential oils of ten Eucalyptus species were obtained by hydro-distillation and examined against Escheichia coli (1330) and Micrococcus loteus (1110). The Eucalyptus species were Eucalyptus gilli, E. microcarpa, E. kingesmillii, E. loxophleba, E. gongylocarpa, E. salubris, E. erythrocorys, E. salmonophloia, E. spathulata and E. flocktoniae. The essential oils were analyzed by capillary GC and GC/MS. Antimicrobial effects of essential oils were evaluated after dilution with dimethyl sulfoxide (DMSO) through agar diffusion method. The results showed that the main component of all essential oils was 1,8-cineole and α-pinene. The highest amount of 1,8-cineole (82.1%) was found in the oil of E. kingesmillii and the lowest amount (59.6%) was found in the oil of E. salubris. The results showed that all oils were effective against two bacteria. The diameters of inhibitory zones on Micrococcus loteus and Escheichia coli were 10 to 49 mm and 10 to 22 mm respectively.