Chemical composition and antimicrobial activity of essential oil of Ocimum kilimandscharicum (R. Br.) Guerke: A new chemotype

Abstract

The hydrodistilled essential oils from the flowers and leaves of Ocimum kilimandscharicum (R. Br.) Guerke growing in Nigeria were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). Nineteen and thirteen constituents representing 98.0% and 99.6% of the flower and leaf oils were identified, respectively. The major components of the flower oil were methyl eugenol (40.4%), borneol (11.9%) and linalool (10.6%) while the leaf oil consisted mainly of methyl eugenol (53.9%) and g-cadinene (16.2%). The antimicrobial activities of the oils were assayed against 12 local bacterial isolates and one reference bacterium using agar-disc diffusion and microdilution-broth methods. The results showed that the oils exhibited a wide range of antimicrobial activities. The mean zones of inhibition (IZ) ranged between 7.3 ± 1.5 and 15.1 ± 1.5 mm in the flower; and 9.3 ± 1.7 and 24.7 ± 1.0 mm in the leaf. The minimum inhibitory concentrations (MIC) values varied between 1.25 and 10 mg/mL (flower) and between 0.16 and 10 mg/mL (leaf). A new chemotype of essential oil of Ocimum kilimandscharicum is described.