A COMPARATIVE EVALUATION OF IN VITRO GROWTH INHIBITORY ACTIVITIES OF DIFFERENT SOLVENT EXTRACTS OF SOME MEDICINAL PLANTS IN NORTHERN GHANA AGAINST SELECTED HUMAN PATHOGENS

Abstract

Bacterial resistance to conventional antibiotics justifies the need to explore alternative remedies from medicinal plants since they represent a rich source of antimicrobial agents. We present a comparative evaluation of in vitro antibacterial activities of different solvent extracts of seven medicinal plants used to treat bacterial infections amongst the tribes of Northern Ghana. In the present study, extracts of the plants were obtained using solvents of different polarities and their growth inhibitory activity against Salmonella typhi and Escherichia coli evaluated in vitro. Phytochemical screening revealed the presence of alkaloids, saponins, tannins, coumarins and flavonoids in most of the extracts. These secondary metabolites have been implicated as antibacterial agents in several reports. The extracts from the seven plants showed varied antibacterial activity against the test organisms. Of the bacteria tested, Salmonella typhi was the least susceptible to most of the extracts. The ethanol extracts of the plants generally demonstrated superior growth inhibitory activity at 100 and 200mg/ml concentrations while the aqueous extracts were the least active at similar concentrations. The maximum antibacterial activity was recorded for Khaya senegalensis ethanol stem bark extract against Escherichia coli (zone of inhibition = 20.10mm) and Salmonella typhi (zone of inhibition = 17.10mm) at 200mg/ml. The result presents the basis for which these plants have been used for treatment of bacterial infections in folkloric medicine. The results further reveal that ethanol stem bark extract of K. senegalensis demonstrated the greatest activity and thus can be very useful in the search for novel antibacterial agents.