Antimycobacterial activity of aqueous and methanol extracts of nine plants against Mycobacterium bacteria

Purpose: The present study was done to evaluate the antimycobacterial activity of aqueous and methanol extracts of nine plants viz., Buddleja saligna, Carpobrotus dimidiatus, Capparis tomentosa, Dichrostachys cinerea, Ekebergia capensis, Ficus sur, Gunnera perpensa, Leonotis leonurus and Tetradenia riparia in South Africa. Methods: Aqueous and methanol extracts of the leaves the plants were tested in vitro for their activity against Mycobacterium smegmatis, Mycobacterium tuberculosis H37Rv (ATCC 25177) and three well-characterized clinical isolates of MDR and XDR-TB isolates using the agar incorporation method. The minimum inhibitory concentration (MIC) of each of the active plant extract was determined using the broth microdilution method. Cytotoxic effect was evaluated against the mouse BALB/C monocyte macrophage (J774.2) and peripheral blood mononuclear cells (PBMCs) whole the toxicity screening was done using the brine shrimp lethality assay. Composition of each of the plants was determined using thin layer chromatography while qualitative analysis of antimycobacterial compounds was done using TLC-Bioautography Results: The methanol extracts of B. saligna, C. tormentosa and C. dimidiatus; and aqueous extracts of G. perpensa and T. riparia possessed significant activity against M. smegmatis, M. tuberculosis H37Rv (ATCC 25177) and the three well-characterized clinical isolates of MDR and XDR-TB. Except for a high concentration of G. perpensa none of the other plants which possessed antimycobacterial activity showed any toxic or cytotoxic activity. Conclusion: Our findings show that B. saligna, C. tormentosa, C. dimidiatus, G. perpensa, and T. riparia have antimycobacterial activity. Further studies would aim at isolation and identification of the active compounds from the plants extracts which had positive antimycobacterial activity.