Antibacterial Activity of Acacia nilotica Stem-Bark Fractions against Staphylococcus aureus and Escherichia coli

Abstract

Aims: This research was carried out to determine the antibacterial activity of Acacia nilotica stem bark extract and bioactive fractions against the test bacteria (Staphylococcus aureus and Escherichia coli). Place and Duration of Study: Acacia nilotica was collected within Aliero town, Kebbi State, Nigeria between April and September, 2017. Methodology: The crude and bioactive fractions were obtained using soxhlet extraction and column chromatographic method respectively. The qualitative phytochemical screening was conducted to detect the presence of some phytochemical constituents in the crude extract and fractions. The antibacterial activity was determined at various concentrations (10, 50, 100, 150 and 200 mg/ml) using disc diffusion method. Results: The crude antibacterial activity indicated that ethanol extract showed higher activity than the n-hexane extract with 14.0±0.00 and 12.0±0.00 mm zones of inhibition compared with the control drug (10 µg Ciprofloxacin drug), which showed 14.0±0.00 and 13.0±0.00 mm zone of inhibition against the test bacteria. The MIC and MBC values determined for ethanol extracts against the test bacteria was 12.5 mg/ml and 25 mg/ml, while the MIC and MBC values obtained for n-hexane extracts were 25 and 50 mg/ml against the test bacteria. The bioactive fractions (Yellow, Purple and Blue Black Fractions) tested against the test bacteria showed higher activity compared with the crude extract. The phytochemical properties of the plant crude extract and the bioactive fractions indicated the presence of phenol, tannins, alkaloids, saponins, flavonoids, terpenoids, steroids and glycosides and  this attributed to the high antibacterial activities of 17.0±0.00 and 16.0±0.00 mm showed by the fractions against Staphylococcus aureus and 15.67± and 14.0±0.00 mm against Escherichia coli respectively. Conclusion: Acacia nilotica crude extract and fractions exhibited antibacterial activity which was comparable to the standard drug ciprofloxacin. This validates the folkloric medicinal use of this plant by the indigenous people of Aliero, Kebbi State.