Abstract
Medicinal plants serve as an important source of natural bioactive compounds that support human health and are widely utilized in the treatment of various diseases. Their therapeutic potential lies in their ability to enhance antifungal and antioxidant activities, inhibit bacterial growth, and modulate genetic pathways involved in disease processes. This study was designed to evaluate the phytochemical composition and antibacterial efficacy of Acacia nilotica leaf crude extracts against bacterial isolates of Escherichia coli, Staphylococcus aureus, and Salmonella typhi. Phytochemical analysis was conducted using classical (wet chemical) methods, Isolation of fungi isolates was done using direct method and agar well diffusion method was used to determine the antibacterial activity. The result of phytochemical screening indicates the presence of tannins, steroids, saponins, glycosides, phenols, alkaloids, flavonoids and terpenoids. The result of quantitative phytochemical result showed that tannins has the highest content (24.70±0.709 %) and steroids with the lowest content (1.16±0.081 %). The result of antibacterial activity of methanolic crude extracts showed higher antibacterial activity against E. coli for all the tested concentrations ranging from (7.76±0.03 to 12.56±0.03 mm), and S. typhiwith the lowest antibacterial activity ranging from (1.76±0.03 mm) to (6.76±0.03 mm). From the fractionation result of antibacterial activity, only sub-fraction A3, A4, A5 and A6 showed the antibacterial activity, A3 (0.00±0.00 to 0.36±0.03 mm) A4 (1.46±0.03 to 9.53±0.03 mm) A5 (2.53±0.03 to 5.06±0.03 mm) and A6 (2.53±0.03 to 4.03±0.03 mm). Sub-fraction A1, A2, A7, A8 and A9 showed zero activity. The antibacterial evaluation of Acacia nilotica leaf extracts against the tested bacterial isolates revealed that the extracts produced stronger inhibitory effects on E. coli than on S. aureus and S. typhi. This finding suggests that Acacia nilotica leaf extracts could serve as a promising source for the development of new antibiotic agents.

Key words: Antibacterial activity, Acacia nilotica, Sub-fractions, Medicinal plants, Phytochemicals