Abstract Infectious diseases caused by bacteria, fungi, parasites and viruses are still a major threat to public health. Their impact is particularly large in developing countries due to the relative unavailability of medicines and the emergence of widespread drug resistance. This has lead to the search of new antimicrobial agents mainly among plant extracts. As part of our ongoing research to purify, isolate and characterized antibacterial compounds from the extracts of some Nigerian medicinal plants, Acacia nilotica (Linn.), Sclerocarya birrea (A. Rich, Hochst.) and Parkia biglobosa (Jacq) were screened for their preliminary phytochemical and antibacterial activity. The preliminary phytochemical screening of the extracts was carried out using standard methods while the antibacterial activity was done using disc diffusion method. The results for the phytochemical secreening showed the presence of most of the phytochemicals tested. The results for the antibacterial activity of the crude methanolic extracts of the plants showed varying degree of antibacterial activity against the bacterial isolates. The extracts at a concentration of 100 mg/mL were found to inhibit the growth of most of the test bacterial isolates comprising of both Gram-positive and Gram-negative organisms. These findings support previous reports on the antimicrobial activity of these plants. However, Acacia nilotica leaves extract shows relatively high (18.00 ± 2.00 for P. aeruginosa and 22.67 ± 0.58 for K. Pneumonia.) zone of inhibition than all the other plants part used. The result of the present study signifies the potential of Acacia nilotica leaf as a source of therapeutic agents, which may provide leads in the ongoing search for antimicrobial agents from plants.
Keywords Acacia nilotica, Sclerocarya birrea Parkia biglobosa, phytochemicals, zone of inhibition.