Abstract
Agar well diffusion techniques and macrobroth dilution methods were used to screen the ethanolic leaf extracts of four medicinal plants (Picralima nitida, Chromolaena odorata, Aspilia africana and Hyptis suaveolens) for antibacterial activity against the following bacterial pathogens: Escherichia coli, Pseudomonas aeruginosa, Salmonella spp., Staphylococcus aureus and Bacillus cereus. The minimal inhibitory concentration (MIC) of P. nitida ranged from 1.56 mg/ml to 6.25 mg/ml and that of C. odorata ranged from 2.0 mg/ml to 7.8 mg/ml, while that of A. africana and H. suaveolens varied from 1.56 mg/ml to 4.69 mg/ml and 6.25 mg/ml to 31.25 mg/ml respectively. The extracts appeared to perform best at concentration of 100 mg/ml in agar well diffusion with average inhibition zone diameters ranging from 15 mm to 21 mm (for P. nitida), 16 mm to 22 mm (for C. odorata), 15 mm to 20 mm (for A. africana) and 11 mm to17 mm (for H. suaveolens). P nitida was the most active extract against E. coli and Salmonella spp (P < 0.05), while C. odorata and A. africana were the most active against P. aeruginosa and S. aureus. The phytochemical screening of the crude extracts revealed the presence of varied concentrations of bioactive compounds including tannins, flavonoid, alkaloid, etc. The results provide justification for the use of these plants in treatment of various infections in herbal medicine.