African Journal of Biotechnology Vol. 6 (6), pp. 760-765, 19 March 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Chemical composition and antimicrobial activity of the essential oil of Ocimum gratissimum L. growing in Eastern Kenya

Lexa G. Matasyoh¹*, Josphat C. Matasyoh², Francis N. Wachira³, Miriam G. Kinyua⁴, Anne W. Thairu Muigai¹ and  Titus K. Mukiama ⁵

¹Department of Botany, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000, Nairobi, Kenya.

²Department of Chemistry, Egerton University, P.O. Box 536, Njoro, Nakuru, Rift Valley, Kenya.

³Department of Biochemistry, Egerton University, P.O. Box 536, Njoro, Nakuru, Rift Valley, Kenya.

⁴Kenya Agricultural Research Institute, P.O. Njoro, Nakuru, Kenya.

⁵Department of Botany, Nairobi University, P.O. Box 29053, Nairobi, Kenya.

*Corresponding author. E-mail: lexa111@hotmail.com.  Tel: +254 722614696

Accepted 10 November, 2006

Hydro-distilled volatile oils from the leaves of Ocimum gratissimum L. (Lamiaceae) from Meru district in Eastern Kenya were analysed by gas chromatography-mass spectrometry (GC-MS) and also evaluated for antimicrobial activity. The oil was dominated by monoterpens which accounted for 92.48%. This monoterpene fraction was characterized by a high percentage of eugenol (68.8%). The other major monoterpenes were methyl eugenol (13.21%), cis-ocimene (7.47%), trans-ocimene (0.94%), β-pinene (1.10%) and camphor (0.95%). The sesquiterpenes present in fairly good amounts were germacrene D (4.25%) and trans-caryophyllene (1.69%). The minor sesquiterpenes were α-farnesene (0.85%) and β-bisabolene (0.74%). The antimicrobial activities of the essential oils were evaluated against both Gram positive (Staphylococcus aureus, Bacillus spp.) and Gram negative (Escherichia coli, Pseudomonas aeruginosae, Salmonella typhi, Klebisiella pneumoniae, Proteus mirabilis) bacteria and a pathogenic fungus Candida albicans. The oil had pronounced antibacterial and antifungal activities on all the microbes.

Key words: Antimicrobial activity, Ocimum gratissimum L., eugenol, methyl eugenol.