ABSTRACT

Medicinal plants have been used for centuries as sources of remedies for management of diseases. These medicinal plants represent potential sources for novel antibacterial compounds. In this study, methanolic extracts of fifteen medicinal plants were screened for antimycobacterial properties using Mycobacterium smegmatis ATCC 19420. The extracts were also tested against two bacterial species Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC25923. Agar dilution and Agar well diffusion techniques were used to assay for the antimycobacterial properties. The crude methanol extract of the leaves of Alchornea cordfolia produced a remarkable inhibitory effect against M smegmatis with inhibition zone of 15.5±0.70mm at 100mg/ml concentration. Similarly, at a concentration of 100mg/ml for Garcinia kola, a diameter zone of inhibition of 18.0±1.41mm was observed while the methanol extract of Asystacia gangetica at concentration of lO0mg/ml, 17.5±0.70mm was observed as the zone of inhibition. Pterocarpus santalinoides produced the least zone of inhibition of 12.5±0.70mm at same concentration. The ethyl acetate fraction of Alchornea cordifolia obtained using column chromatography produced substantial inhibitory effect against M smegmatis with inhibition zone of 14.0±0.00mm at 100mg/ml concentration. At the same concentration for dichloromethane: methanol fraction of G. kola, a diameter zone of inhibition of 12.5±0.00mm was observed while 12.0±0.00mm was reported as zone of clearing for the ethyl acetate fraction of C. odorata. No inhibitory activity was observed for the hexane fractions except the hexane fraction of Chromolena odorata which was only active at 100mg/ml with zone of inhibition of 10.0±0.00mm. The inhibitory activities of the test extracts were concentration dependent. The Minimum Inhibitory Concentrations (MIC) determined using the broth dilution assay ranged between 12.5mg/ml to lo0mg/ml for M smegmatis. The ethyl acetate fraction of A. cordfolia produced the highest antimycobacterial activity. The phytochemical screening of the leaf extract revealed the presence of tannins, saponins, flavonoids, alkaloids and terpenoids, some of which may have contributed to the observed antimycobacterial activity. Quantitatively, the percentage yields of phytochemical content of the leaves of the Aichornea cordifolia and Garcinia kola plants were as follows: alkaloids (1.86%,1.23%), flavonoids (1.07%,1.28%), terpenoids (4.02,1.21%), saponins (4.10%,2.91%), and tannins (0.68%,1.82%) respectively. The results from this study showed that the leaf extracts of A. cordfolia, G. kola, A. gangetica, P. santalinoides and C. odorata exhibited interesting antimycobacterial activity.