Abstract

Antibacterial activity of the methanolic leaf extract of Plukenetia conophora Mull. arg. (African walnut) on selected urinary isolates: Pseudomonas aeruginosa, Escherichia coli, Klebsiella aerogenes and Proteus mirabilis, was investigated using the agar punch-hole diffusion and agar broth dilution methods to verify claims by the locals of its medicinal value in the treatment of urinary tract infection. The extract exhibited bactericidal activity against the uro-pathogens in varying degrees at different concentrations tested. In the agar diffusion test, P. aeruginosa showed the highest zone of inhibition (18 mm) at the highest concentration tested (200 mg/mL); while P. mirabilis, K. aerogenes and E. coli showed zones of inhibition of 15, 13 and 12 mm respectively. E. coli and K. aerogenes did not show any zone of inhibition, while P. aeruginosa (14, 12, 10 and 8 mm) and P. mirabilis (13, 11, 8 and 7 mm) showed varied zones of inhibition at extract concentration of 150, 100, 50 and 25 mg/mL, respectively. P. aeruginosa had the least minimum inhibitory concentration (6.25 mg/mL), followed by P. mirabilis (12.5 mg/mL); while E. coli and K. aerogenes has the same MIC (150 mg/mL). The minimum bactericidal concentration (MBC) gave a range of (6.25 – 200) mg/mL. All the isolates had MBC higher than MIC except, P. aeruginosa with sensitivity significantly higher than that of E. coli and K. aerogenes at P<0>0.05). There was no significant difference between the sensitivity of E. coli and K. aerogenes to the extract (P>0.05). Phytochemical screening of the extract, revealed the presence of tannins, anthraquinones, saponins, flavonoids, resins and alkaloids, while cardiac glycosides and steroids were absent. The result further strengthening earlier works on the efficacy of the plant, and it therefore stands a chance for clinical trial as an alternative treatment option for urinary tract infection, though; the molecular mechanism behind its antibacterial activity would require further investigation.