ABSTRACT
Laurus nobilis, generally known as ‘bay leaf or Turkish laurel’ is a small evergreen aromatic shrub or tree belonging to Lauraceae family of plants. It leaves are widely used for food seasoning as well as in folk medicine. This study was aimed at investigating the phytochemical constituents and antibacterial effects of Laurus nobilis on selected pathogens. The phytochemical screening of the leaves was done using standard method. The organism are Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Proteus sp. and Salmonella typhi. Which were obtained from University of Benin Teaching Hospital and confirmatory test was done on the isolate using cultural and biochemical method. Antibacterial susceptibility was done using disc diffusion method and MIC and MBC was done using broth dilution method. The percentage composition of saponin, alkaloid, tannin, flavonoid, and total polyphenol in the L. nobilis leaves are 4.40%, 4.00%, 13.50%, 11.00% and 0.10% respectively. In the extract for 2 days, E. coli and S. typhi were the most inhibited by the aqueous extracts (10.00±0.00 mm and 10.00±0.00 mm respectively), B. subtilis was the most susceptible to the ethanolic extracts (13.00±0.00mm), while methanol had no inhibitory activity against any of the isolates. In the extract after 4 days, P. aeruginosa was the only isolate inhibited by the aqueous extract (11.00±0.00 mm), S. aureus was the most inhibited by the ethanolic extract (8.33±1.33mm), while B. subtilis had incredibly high susceptibility to the methanolic extract (23.00±0.00 mm). In this study, more inhibitory activity was observed against the isolates in the 4 days than the 2 days extracts, and the methanolic extracts had more significant inhibitory activity across the isolates. The most remarkable inhibitionwas found in the methanolic extract against B. subtilis with MIC of 200mg/ml. Also, all the L. nobilis extracts were not bactericidal, rather displayed bacteriostatic activity. In some of the isolates standard antibiotics demonstrate higher inhibition zone compared to the extracts. While in some especially B. subtilis the isolates showed massive resistance to the antibiotics compared to the extract (methanolic). This is promising in that L. nobilis extract offer some potential in the combat of diseases caused by these bacterial agents, and may be screened for activity against several other human and plant pathogens.
