Abstract

O. O. Olajuyigbe and A. J. Afolayan*

The antibacterial activities of both water and ethanol extracts of Acacia mearnsii de Wild against Grampositive and Gram-negative bacteria were investigated. The two extracts were very active against the two groups of bacteria. While the minimum inhibitory concentration (MIC) of the ethanol extract ranged between 78.1 and 625 µg/ml, the MIC for aqueous extract ranged between 156.3 and 625 µg/ml. The minimum bactericidal concentrations (MBC) of ethanol extract ranged between 156.3 and 625 µg/ml while that of aqueous extract was between 312.5 and 5000 µg/ml. Water appeared to be a good extraction medium and its extract could be as potent as alcoholic extracts.The MICindex showed that the two extracts were bactericidal at high concentrations and bacteriostatic at low concentrations. The strong bactericidal activities of the two extracts may be attributed to the presence of some secondary metabolites which are soluble in both ethanol and water. The antibacterial activity of the extracts indicated the great therapeutic potential of this plant and has justified its ethnomedicinal use against infectious diseases.