Evaluation of the Effects of Stem Bark Solvent Extracts of Prosopis africana on Some Pathogenic Bacteria

Background: Prosopis africana is an edible medicinal tree rich in nutrients and bioactive compounds used in traditional medical practice as antimicrobial, anti-inflammatory, analgesic, and antioxidant as well as a condiment. This study was carried out to evaluate the antibacterial activity of Prosopis africana stem bark solvent extracts on selected bacteria isolates. Methods: In this study stem bark solvent extracts were tested for inhibitory activity against bacterial isolates. The bacterial isolates were obtained from microbiology department of Bayero University, Kano Nigeria. Qualitative phytochemical screening showed the presence of alkaloids, saponins, tannins and terpenoids in n-hexane extract, chloroform extract contained alkaloids, cardiac, glycosides, phenols, flavonoids, tannins, and quinones. while ethyl acetate and methanolic stem bark extracts contained alkaloids, cardiac, glycosides, saponins, phenols, flavonoids, tannins, terpenoides and quinones. Antibacterial activites were assessed against six bacterial isolates, Escherichia coli, Klebsiella pneumonia, Salmonella typhi, Shigella dysentriae, Staphlococcus aureous, and Pseudomonas aeruginosa using agar well-diffusion method with gentamicin used as standard. Four different varying concentration of each extract, 12.5 mg/ml, 25 mg/ ml, 50 mg/ml and 100 mg/ml were used. Antibacterial activity was assessed using agar well diffusion minimum inhibitory concentration (MIC) on Meuller-Hinton media in triplicates. Each zone of inhibition was measured and recorded in millimeter. Results: There is concentration dependent increase in antibacterial activities from low to high concentration in all the tested extracts fractions with ethyl acetate (from 12.29 ±1.96 at 12.5 mg/ml to 20.47±2.55 at 100 mg/ml against E. coli), showing most activities higher than other fractions. Conclusion: Prosopis africana stem bark extract contained phytochemicals with antibacterial activities against the tested bacterial isolates. This finding supports the traditional use of Prosopis africana.