Abstract

The antibacterial potency of ethanol, acetone and chloroform leaf extracts of Vernonia amygdalina, Ocimum gratissimum, Corchorous olitorius and Manihot palmata were screened against ten bacterial isolates using the agar-well diffusion method. The leaf extracts were screened for antibacterial activities at 25 mg/ml concentration. Antibacterial efficacy of extracts against the bacterial isolates was indicated by the appearance of clear zones of inhibition around the wells. The extracts (except that of Corchorous olitirious), showed inhibitory activities against Bacillus cereus, Salmonella typhi, Staphylococcus aureus, Shigella dysenteriae andEscherichia coil with zones of inhibition ranging between 2 and 20mm. Result of the antagonistic activity of the extracts compared favourably with the activity of standard antibiotics. The rate of killing by the extracts was carried out, using 50 mg/ml. It was observed that the number of bacterial cells was decreasing as the time of interaction between the extract and the bacteria increased until all cells were killed. Phytochemcial screening of the extracts revealed the presence of some bioactive components like alkaloids, saponins, tannins, anthraquinones, steroids, flavonoids and cardiac glycosides. These properties determine the antimicrobial potential of the leaf extracts.

Key words: Antibacterial activity, phytochemical components, extracts, zone of inhibition.