Antibacterial Activity and Acute Toxicity Study of Acacia nilotica

Abstract

Methanol crude extract and chloroform, ethyl acetate, n-butanol and aqueous fractions of the methanolic extract of fruits and stem bark of Acacia nilotica (L.) Willd. ex Del. (Fabaceae) were screened for antibacterial activity of diarrhoea-causing bacterial species (Escherichia coli, Shigella dysenteriae and Salmonella typhi) in Ethiopia using standard agar dilution method. Oral acute toxicity studies were also carried out on mice with the ethyl acetate fruit fraction of A. nilotica. Compared with standard antibiotic (chloramphenicol and tetracycline) extracts and fractions, A. nilotica had low activity (P<0.05). The ethyl acetate fruits fraction showed antibacterial activity with minimum inhibitory concentration (MIC) of 0.25 mg/ml. n-Butanol fraction of fruits and stem bark of A. nilotica. showed lower activity (P<0.001) than ethyl acetate and chloroform fraction. The aqueous fraction of the plant did not exhibit any activity at concentration of 2 mg/ml. LD50 value of the ethyl acetate fruit fraction was 7393.4 mg/kg with 95% confidence limit of 6019.5-9207.9 mg/kg which was significantly higher in comparison to the active dose of the fraction (P<0.001). Results of this study suggested the potential of this highly active fraction and supported the ethnomedicinal uses of the plant to some extent in Ethiopian traditional medicine to treat diarrhoea.

Keywords: Acacia nilotica; Antibacterial activity; Crude extract; Traditional medicine.

Ethiopian Journal of Biological Sciences Vol. 6 (1) 2007: pp. 4349