A Multi‑Dimensional Evaluation of the Antimycobacterial Activity, Cytotoxicity, and Mechanisms of Action of South African Medicinal Plants Against Mycobacterium smegmatis
1
1 Biochemistry, Microbiology and Biotechnology, University of Limpopo, Polokwane, South Africa
2
2 Centre for TB Research Division of Molecular Biology and Human Genetics, Stellenbosch University, Cape Town, South Africa
Popul. Med. 2026;8(Supplement Supplement 1):A206
ABSTRACT
BACKGROUND:
Tuberculosis remains a major global health challenge, intensified by rising multidrug resistance and the ability of Mycobacterium tuberculosis to persist in dormant states 1,2. Given the limitations of current therapies, medicinal plants offer a potential source of new antitubercular agents 3,4. This study examined how varying concentrations of selected plant extracts influence resistance‑related mechanisms in Mycobacterium smegmatis, with the aim of understanding how natural compounds may disrupt bacterial resistance and support future TB treatment development.
METHODS:
The study determined the antimycobacterial activity of the plant extracts and examined how it corresponds to the extract concentrations effective for antibiofilm activity, metabolic disruption, mechanisms of action and cytotoxicity. Comparative bioactivity analyses were conducted across the different plant extracts to identify the most promising species for further pharmacological exploration. Cytotoxic effects were evaluated using the human leukemia monocytic (THP‑1) cell line.
RESULTS:
The minimum inhibitory concentrations (MICs) of the plant extracts ranged from 310 to 1250 µg/mL, with Polygala myrtifolia exhibiting the most potent antimycobacterial activity. The concentrations required to inhibit biofilm formation and metabolic activity at various developmental stages were significantly lower than the MIC values and differed among the plant species. All extracts were non‑toxic to THP‑1 cell lines, except for Harpephyllum caffrum, which displayed an IC₅₀ value of 18.43 ± 1.13ab µg/mL, indicating measurable cytotoxicity 5. The plant extracts disrupted the membrane integrity of M. smegmatis as shown by the protein and DNA leakage which was proportional to extract concentrations 6,7.
CONCLUSIONS:
The plant extracts showed strong antimycobacterial activity, with P. myrtifolia most effective. Sub MIC levels reduced biofilms and metabolic activity, indicating disruption of persistence mechanisms. Most extracts were non toxic to THP 1 cells, though H. caffrum showed some cytotoxicity. Overall, these plants appear promising sources of new antimycobacterial agents.
Tuberculosis remains a major global health challenge, intensified by rising multidrug resistance and the ability of Mycobacterium tuberculosis to persist in dormant states 1,2. Given the limitations of current therapies, medicinal plants offer a potential source of new antitubercular agents 3,4. This study examined how varying concentrations of selected plant extracts influence resistance‑related mechanisms in Mycobacterium smegmatis, with the aim of understanding how natural compounds may disrupt bacterial resistance and support future TB treatment development.
METHODS:
The study determined the antimycobacterial activity of the plant extracts and examined how it corresponds to the extract concentrations effective for antibiofilm activity, metabolic disruption, mechanisms of action and cytotoxicity. Comparative bioactivity analyses were conducted across the different plant extracts to identify the most promising species for further pharmacological exploration. Cytotoxic effects were evaluated using the human leukemia monocytic (THP‑1) cell line.
RESULTS:
The minimum inhibitory concentrations (MICs) of the plant extracts ranged from 310 to 1250 µg/mL, with Polygala myrtifolia exhibiting the most potent antimycobacterial activity. The concentrations required to inhibit biofilm formation and metabolic activity at various developmental stages were significantly lower than the MIC values and differed among the plant species. All extracts were non‑toxic to THP‑1 cell lines, except for Harpephyllum caffrum, which displayed an IC₅₀ value of 18.43 ± 1.13ab µg/mL, indicating measurable cytotoxicity 5. The plant extracts disrupted the membrane integrity of M. smegmatis as shown by the protein and DNA leakage which was proportional to extract concentrations 6,7.
CONCLUSIONS:
The plant extracts showed strong antimycobacterial activity, with P. myrtifolia most effective. Sub MIC levels reduced biofilms and metabolic activity, indicating disruption of persistence mechanisms. Most extracts were non toxic to THP 1 cells, though H. caffrum showed some cytotoxicity. Overall, these plants appear promising sources of new antimycobacterial agents.
| eISSN: | 2654-1459 |
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