Abstract

 
 
 
 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.
 
 
 
Highlights
Mycobacterium tuberculosis is the etiologic agent of tuberculosis (TB) in humans which infects about one-third of the world’s population [1].Despite more than forty years of antimycobacterial chemotherapy, TB remains one of the leading infectious disease killers worldwide
Our findings show that B. saligna, C. tormentosa, C. dimidiatus, G. perpensa, and T. riparia have antimycobacterial activity
Only the aqueous extracts of G. perpensa and T. riparia; and methanol extracts of B. saligna, C. tormentosa and C. dimidiatus showed activity against M. smegmatis and M. tuberculosis H37Rv ATCC 25177 (Table 2). These plant extracts were the ones selected for further antimycobacterial study against three well-characterized clinical isolates of MDR-TB and three well-characterized clinical isolates of XDR-TB
Summary
Mycobacterium tuberculosis is the etiologic agent of tuberculosis (TB) in humans which infects about one-third of the world’s population [1].Despite more than forty years of antimycobacterial chemotherapy, TB remains one of the leading infectious disease killers worldwide. As at 2015, there were an estimated 10.4 million new cases of TB disease worldwide. Natural sources provide numerous examples of interesting secondary metabolites with antimycobacterial activity, indicating that natural products could be rewarding in the discovery of new antimycobacterial leads [6]. Medicinal plants offer a great hope to fulfill these needs and have been used for curing diseases for many centuries. These have been used extensively either as pure compounds or crude materials [7]. Many orthodox medicines are expensive or inaccessible making it very necessary to validate the efficacy and safety of plant sources of medicines
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