No abstract

The phytochemical screening, antibacterial and toxicological activities of extracts of the leaves, stem bark and roots of Acacia nilotica were investigated. The phytochemical analyses according to standard screening tests using conventional protocols revealed the presence of tannins and sterols in the leaves stem barks and roots of the plant. Alkaloids were detected only in the leaves. Glycosides, saponins, resins and flavonoids were not detected in the plant. In-vitro agar-diffusion sensitivity tests of crude extract fractions of the plant extracts using ethanol, chloroform, methanol, petroleum ether, water and ethyl acetate were investigated on nine bacterial isolates. The extract fractions generally exhibited marked antibacterial activities on Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhi, Shigella dysenteriae Staphylococcus aureus and Escherichia coli except on Streptococcus pneumoniae and Streptococcus pyogenes. All the leaves extract fractions of the plant exhibited weak or no antibacterial activity on the bacterial isolates tested but the stem bark and root extracts generally exhibited strong antibacterial activities on them. The minimum inhibitory concentration and minimum bactericidal concentration studies revealed that some bacterial isolates were inhibited at concentrations of about 12.5mg/ml and 50mg/ml and killed at concentrations of about 100mg/ml and 400mg/ml. Toxicity studies of the ethanol extracts revealed that they exhibited no significant toxicity (LD 50 of 123.86µg/ml and312.55µg/ml) against Artemia salina . These results suggest that the plant may not be toxic to man and could be a potential source of novel antibacterial compound.