Abstract

Trichilia roka (Forsk) Choiv, Tridax procumbens Linn and Maerua angolensis DC are medicinal plants commonly used in traditional medicine to treat various diseases. The aims of this study were to screen the extracts of the leaves of the three medicinal plants for phytochemicals, and to determine the antimicrobial activity of the extracts against nine common strains of bacteria and one yeast strain. The extraction of the leaves was performed using methanol and petroleum ether. The phytochemical screening and the antimicrobial activity of the extracts were carried out using standard laboratory methods. The results of the phytochemical screening showed that the methanol extracts contained tannins, saponins, flavonoids, cardiac glycosides and alkaloids. The minimum inhibitory concentrations (MICs) of the methanol extracts of  M. angolensis and T. roka ranged between 6.25 and 25 mg/ml for all the test microorganisms, while those of petroleum ether extracts of M. angolensis and T. procumbens obtained for Bacillus subtilis were 6.25 and 12.5 mg/ml, respectively. The petroleum ether extract of T. roka was active againstStreptococcus pyogenes, Escherichia coli and Neisseria gonorrhoeae, and the MIC was between 6.25 and 12.5 mg/ml. The methanol extracts of the plants were demonstrated to possess greater inhibitory activity against the pathogenic microorganisms than the petroleum ether extracts. In conclusion, the results of the study support the use of the plants in traditional phytomedicine for the treatment of diseases caused by the microorganisms.

Key words: Trichilia roka, Tridax procumbens, Maerua angolensis, secondary metabolites, antimicrobial activity.