essential oil components and biological activities of coleus parvifolius leaves

The essential oil distilled from the leaves of Coleus parvifolius Benth. (Labiatae) was studied by gas chromatography and mass spectrometry (GC-MS). The main components were found to be (E)-phytol (42.77%), followed by eicosatrienoate (16.39%), n-tetradecanoic acid (14.42%), octoil (6.54%), 2-methyl-7- octadecyne (5.97%), nonadecane (3.25%), germacrene-D (2.19%) and α-humulene (1.42%), respectively. Regarding biological activities, the ethanolic extract of C. parvifolius showed potent antimicrobial activity against gram positive bacteria (Staphylococcus aureus, Bacillus subtilis and B. cereus) with inhibition zones of 7-11 mm at a concentration of 10 mg/disc and moderate activity against gram negative bacteria (Salmonella typhi, S. enteritidis and Escherichia coli) with inhibition zones of 9-11 mm at 100 mg/disc, whereas it was inactive against fungus, Candida albicans at a concentration of 100 mg/disc. The extract also exhibited strong antioxidant activity (ED50 = 5.87±0.03 μg/ml) three times higher than that of butylated hydroxytoluene (BHT, ED50 = 18.08±0.43 μg/ml). Moreover, it was non-toxic to brine shrimp with LC50 value > 1,000 μg/ml.