Effect of Collection Time on Chemical Composition and Antibacterial Activity of Flower Essential Oil of Ocimum canum (Sims) Grown in Nigeria.

Abstract

Flowers (1000 g) of Ocimum canum harvested at different times (7 am, 10 am, 1 pm, 4 pm, and 7 pm) in a day were separately hydrodistilled and yielded 0.19 - 0.27% (w/w) of essential oils. GC and GC-MS analyses revealed that the oils were predominated by oxygenated monoterpenoids (51.2-74.4%). Hydrocarbon monoterpenoids constituted 6.2-10.2% of the oils. Percentage composition of hydrocarbon and oxygenated sesquiterpenoids in the oils were in the range of 1.3-22.0%. The most abundant constituent of the oils was linalool (40.5-58.7%). Other principal constituents were as follows: Limonene (0.6 –7.5%), terpinen-4-ol (1.4–5.6%), eugenol (4.4–8.9%), geranyl acetate (0.2–4.9%), α-trans-bergamotene (3.2–9.4%) and (E)-isoeugenol (4.1–5.5%). The predominance of linalool in the oils showed that the oils were of linalool chemotype. Antibacterial activity of the oils was evaluated against Staphylococcus aureus and Escherichia coli using agar diffusion method. Irrespective of the time of collection of the flower, the oils were found to be active against the tested organisms. However, they are more active on Escherichia coli than Staphylococcus aureus. The activity of the oils on the organisms was concentration-dependent.