Antimycobacterial effects of stem bark and wood extracts of African medicinal plants Terminalia laxiflora and Terminali brownii

Terminalia brownii and Terminalia laxiflora are popular medicinal plants in Africa, used for treatment and prevention of various ailments and diseases, among them tuberculosis and related symptoms. Decoctions of the leaves, bark and roots are used against cough in Sudan. Tuberculosis is common in sub-Saharan Africa and the incidence of antibiotic resistant Mycobacterium tuberculosis is increasing. New antimycobacterial compounds could be found from African medicinal plants. The purpose of this study was to investigate the growth inhibitory effects of extracts of different polarities of T. brownii and T. laxiflora against Mycobacterium smegmatis using modified agar disk diffusion and microdilution methods [1,2]. M. smegmatis is commonly applied as a model organism due to its similarity to M. tuberculosis as well as its relative resistance to rifampicin. Acetone extracts of the leaves and cold water extracts of the roots of T. brownii gave significant growth inhibitory effects with inhibition zones of 27.0 and 26.7 mm and MIC 2500 and 5000 µg/ml, respectively. In addition, hot water decoctions of the roots of T. brownii gave significant growth inhibitory results. Compared to stem wood, bark and leaf extracts, the root of T. laxiflora gave the best antimycobacterial effects and especially acetone (MIC 625 µg/ml), methanol and ethyl acetate extracts (MIC 1250 µg/ml) gave good activities. A hot water decoction of T. laxiflora roots showed slight antimycobacterial activity. Our results support the traditional uses of the roots of T. brownii as hot water decoctions for treatment of tuberculosis and cough.