Research Article
Iyamu, M. I., Ekozien, M.I. &
Abstract
Acetone, ethanol, n-hexane, petroleum ether and aqueous (cold and hot) extracts of the stem bark of African Locust Bean Plant (Parkia filicoidea Welw.) were tested against six bacterial isolates: Staphylococcus aureus NCTC 10788, Bacillus subtilis, Streptococcus viridans, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae using the agar well diffusion method. The crude powdered plant samples of the stem bark were subjected to phytochemical screening using standard methods to test for the presence of carbohydrates and reducing sugars, anthraquinones, cardiac and cyanogenetic glycosides, saponins, tannins flavonoids and alkaloids. The hexane and petroleum ether extracts of the stem bark including the control solvents distilled water and dimethylsulphoxide (DMSO) exhibited no antibacterial activity. The aqueous (hot and cold) extracts of the stem bark were generally active against the Gram positive bacteria S. viridans and B. subtilis including the control organism S. aureus NCTC 10788 with a zone of inhibition which ranged from 17.00 ± 1.73 mm to 19.30 ± 0.46 mm and 17.67 ± 0.67 mm to 23.17 ± 1.51 mm respectively. Acetone and ethanol extracts were active against both the Gram positive and Gram negative organisms E. coli and P. aeruginosa and K. pneumoniae with a zone of inhibition which ranged from 18.33 ± 2.32.58 mm to 21.50 ± 0.00 mm and 13.00 ± 0.00 mm to 20.00 ± 2.08 mm respectively. The minimum inhibitory concentration (MIC) for the bioactive extracts ranged from 2.50 to 20.00 mgml-1 . The test organisms were generally more sensitive to the commercial antibiotics gentamicin, ciprofloxacin and amoxicillin than the plant extracts with a zone of inhibition which ranged from 16.96 ± 0.09 mm to 29.30 ± 0.36 mm; E. coli and K. pneumoniae were not sensitive to amoxicillin. The results of the phytochemical screening showed that carbohydrates, reducing sugars, saponins, tannins and flavonoids were present.