Anti-Mycobacterial Activity of Medicinal Plant Extracts Used in the Treatment of Tuberculosis by Traditional Medicine Practitioners in Uganda

Tuberculosis (TB) remains a public health challenge and one of the leading causes of death worldwide. TB is preventable and curable. However, treatment of tuberculosis has continued to be difficult as a result of rapid increase of multidrug and extensively drug resistant strains of Mycobacterium tuberculosis. Medicinal plants have for centuries been traditionally used in treatment of tuberculosis and similar ailments. They possess antimicrobial properties which render them a new hope as a source of novel bioactive leads in the development of antimycobacterial agents. In this study, 2 plant species commonly used traditionally in Uganda for treatment of tuberculosis, Zanthoxylum leprieurii and Rubia cordifolia were screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis strains; pan sensitive MTB H37Rv, Rifampicin resistant TMC 331 strain and two wild strains (one rifampicin resistant and another one rifampicin susceptible). Antimycobacterial activity of aqueous, ethanolic and methanolic plant extracts was determined using Resazurin Microtiter Assay (REMA). Both plant extracts exhibited significant in vitro antimycobacterial activity against all strains of Mycobacterium tuberculosis. Minimum inhibitory concentrations (MIC) of methanolic crude extracts of both plants ranged from 23.4 μg/mL to 187.5 μg/mL. Comparatively, methanol extracts of both plants possessed superior antimycobacterial activity against all Mycobacterium tuberculosis strains. Our findings indicated that both plants exhibited activity against susceptible and resistant strains of Mycobacterium tuberculosis. While antimycobacterial activity of Z. leprieurii confirms results from previous studies, activity of the extracts of R. cordifolia is reported for the first time in East Africa. Further studies aimed at determining the effects of combination of these plant extracts and standard anti-TB drugs should be carried out.