Comparative studies of constituents and antibacterial activities of leaf and fruit essential oils of Ocimium basilicum grown in north central Nigeria.

Abstract

Leaves and fruits (500g each) of Ocimum basilicum that were separately hydrodistilled, yielded 0.4 and 0.5% (v/w) of the oils respectively. Analyses of the oils using GC and GC-MS showed that, bulk of the oils were constituted by oxygenated monoterpenes. The principal constituents of the leaf and fruit oils were; linalool (61.7 and 62.9%), 1,8-cineole (17.2 and 18.7%), borneol (8.5 and 6.4%), eugenol (5.7 and 5.4%) and α-caryophyllene (4.3 and 4.0%). With the predominance of linalool in the oils, they are of linalool chemotypes. The antibacterial activities of the oils were evaluated on ten clinical bacterial isolates using disc diffusion method. The oils were found to inhibit three Gram-positive and three Gram-negative bacteria. The bacteria inhibited were Bacillus megaterium, Bacillus cereus, Streptococcus pyogenes, Escherichia coli, Proteus mirabilis and Klebsiella pneumonia. Bacillus megaterium had the highest susceptibility with minimum inhibitory concentration (MIC) of 2.5 mg ml-1 .Bacillus cereus, Streptococcus pyogenes, Serratia marcescens and Pseudomonas aeruginosa showed resistance to the oils.