IN-VITRO ANTIMICROBIAL ACTIVITIES OF SODOM APPLE (CALOTROPIS PROCERA) AND BITTER LEAF (VERNONIA AMYGDALINA) EXTRACTS AGAINST SOME MEDICALLY IMPORTANT PATHOGENIC BACTERIA

Abstract

Plants have been used for generations as source of medicine in the treatment of a variety of human illnesses. In Ethiopia, many plants are used for this purpose by traditional healers without any scientific justification for their therapeutic values. Thus, this study was aimed atassessing the antibacterial activities of crude extracts obtained from different parts of Calotropis procera and Vernonia amygdalina against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The stems, roots and leaves of the selected plant species were shade dried and ground to powders and the bioactive components were extracted using ethanol (99.5%), methanol (99.8%), hexane (99.8%) and distilled water. The antibacterial activities of the resulting extracts against the three selected pathogens were evaluated using the paper disc method and the inhibitory zones were recorded in millimeters. Minimum inhibitory concentrations (MICs) of the plant extracts against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were assessed using the agar dilution method. Chloramphenicol and sterile distilled water were used as positive and negative controls, respectively. The bioassay studies of the crude extracts were undertaken at five different concentrations (20, 30, 40, 50 and 60 mg/ml). The results revealed that the crude extracts of ethanol, methanol, hexane and water had antibacterial activities on all three bacterial species except at 20 mg/ml of all solvent extracts. Methanol and ethanol extracts had the highest growth inhibitory effects as compared with those of the aqueous and hexane crude extracts. However, the four solvent crude extracts had less antibacterial activities than chloramephenicol. S. aureus was found to be the most susceptible pathogen to the crude ethanol (99.5%) and methanol (99.8) extracts of the leaves of Vernonia amygdalina (22 mg/ml) and ethanol extract of the leaves of Calotropis procera (22 mg/ml). Whereas Pseudomonas auruginosa was the least susceptible bacterium to crude ethanol extract (99.5%) of the root of Calotropis procera at 28 mg/ml and crude water extract of the root of Vernonia amygdalina at 28 mg/ml. The growth inhibitory activities of the crude extracts were found to be significantly different for the four concentrations (30, 40, 50 and 60mg/ml) in both plant parts (p < 0.05).