Antibacterial and Potential Toxicological Evaluation of Leaf Extracts of Guiera senegalensis against Gram Negative Bacteria

Objective: To evaluate the antibacterial and potential toxicity effects of leaves extract of Guira senegalensis.

Methods: The plant material was extracted with methanol and aqueous solvents using sohxlet extractor and assayed for qualitative/quantitative phytochemicals. The extracts were bioassayed against clinical isolates of selected gram negative bacterial (Echerichia coli, Salmonella typhi, Klebsiela pneumoniae and Pseudomona aeruginosa). Tetracycline and chloramphenicol were used as positive standard drugs. Acute toxicity studies were conducted by administering different doses (100, 200, 400, 600, 800, 1000, 1200 mg/kg) of the extract to eight groups (4 animals per group). A ten weeks sub acute toxicity investigation was also conducted in rats.

Results: Analysis showed that the extracts contain alkaloids, phenols, tannins, steroids and saponins. Estimation of the phytochemicals revealed high concentration between 87.3±0.5 g/ml and 123.3±0.34 g/ml of phenols, while saponins, flavonids, tannins and alkaloids were present in less amounts and at varied concentrations. The aqueous extract shows appreciable antibacterial activity when tested at 40 mg/ml concentration against all isolates with diameters zone of inhibitions ranging 14.40±1.60 mm to 15.60±0.51 mm. Tetracycline and chloramphenicol demonstrated higher inhibitory zones than the plant extract. Low MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) values were observed for E. coli, K. pneumonia, P. aeruginosa except S. typhi. The selected safe dose was 800 mg/kg and the LD50 value was estimated to be 894.43 mg/kg. Haematological, and biochemical analysis revealed no toxic effects after weeks 1 and 5 of treatment. However, cumulative toxic effects were manifested after week 10 of treatment. The result of liver and kidney histopathology revealed mild necrosis of the hepatocytes and gross nephrotoxicity.

Conclusion: Although the leaf extracts of G. senegalensis appeared to be relatively safe, potential hepatic and renal toxicity may occur with prolonged usage.