Abstract

The antibacterial activity of aqueous and ethanolic extracts of two Nigerian medicinal plants, Euphorbia heterophylla and Jatropha curcas was investigated using disc agar diffusion and broth dilution assays against four clinical isolates of bacteria consisting of two gram positive (Staphylococcus aureus and Enterococcus faecalis) and two gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The antibacterial activity was measured by the diameter zone of inhibition and minimum inhibitory concentration (MIC). The extracts exhibited broad spectrum antibacterial activities against the microorganisms. The diameter of zone of inhibition ranged from 10-15 mm at 2000 μg of crude extract per disc. The MIC values were between 125 -1000 μg/ml. The results of this study indicate that these plants contain compounds with antibacterial activity which validates their use for treatment of various microbial infections in traditional medicine. The findings in this study provide the basis for further study on the plants with the aim of isolating and identifying the active substances. The plants could also be standardized to develop cheap, culturally acceptable herbal medicines.

Key words: Antimicrobial activity, medicinal plants, Jatropha curcas, Euphorbia heterophylla, minimum inhibitory concentration.