Leaf Essential oils of <i>Salvia nilotica</i> and <i>Salvia schimperi</i>: Their Antimicrobial and Antioxidant Activities

Abstract

The compositions of the essential oils of the leaves of Salvia nilotica and Salvia schimperi were analyzed by gas chromatography-mass spectrometry (GC-MS). The results of the analyses indicated that the components of the two oils are qualitatively similar with significant quantitative differences. Twenty-seven compounds comprising 84.73% of the total peak areas were identified in S. nilotica oil with germacrene D (28.48%), guaiol (13.99%), and trans-caryophyllene (12.96%) as major components. The essential oil of S. schimperi was found to contain 42 compounds accounting for 88.3% of the total peak area, the major components being linalool (44.35%), and α-terpineol (9.27%). The in vitro antimicrobial activity of the essential oils of both plants were studied against a wide range of medically important pathogens including Grampositive and Gram-negative bacteria, as well as some fungal strains using a standard disc diffusion technique. The results revealed that the oils possessed significant activity against most of the bacterial and fungal strains used in the study. The minimum inhibitory concentration (MIC) values ranged from 25 to 100 μg/ml against the bacteria and 1000 to 1500 μg/ml against the fungi. At similar concentrations, the oils and the standard antibiotic ciprofloxacin exhibited similar activities against various Gram-positive and Gramnegative bacterial strains. In addition, the essential oils of both plants were demonstrated to have a strong free-radical scavenging potential in 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. In light of the results obtained, it could be concluded that the study supports the various uses of S. nilotica and S. schimperi in traditional medical practices of Ethiopia.

Keywords: Salvia nilotica, Salvia schimperi, essential oils, antimicrobial activity, radical scavenging potential

Ethiopian Pharmaceutical Journal Vol. 26 (1) 2008: pp. 49-58