Antimycobacterial compounds isolated from medicinal plants: A South African comprehensive review

The current review aims at documenting the antimycobacterial compounds and derivatives against a plethora of pathogenic and non-pathogenic Mycobacteria. In South Africa, the indigenous people of different ethnic groups use medicinal plants to treat various Mycobacterial infections. However, the active ingredients, mode of action and safety profiles are not known to such lay people. A total of 117 antimycobacterial compounds were isolated, characterised, and synthesised from 35 medicinal plants belonging to 24 different families. The most dominant family was Asteraceae (20.83 %), followed by Combretaceae (16.67 %), and then Lamiaceae (12.5 %), Malvaceae and Rutaceae with 8.33 % apiece. The diversity of such compounds favoured the naphthoquinones (22.22 %), flavonoids (19.66 %), triterpenes (14.53 %), terpenes (10.26 %), steroids and glycosides (7.69 %), and coumarins (5.13 %). Naphthoquinones are well studies and compounds such as 7-methyljuglone and shinanolone from Euclea natalensis exhibited notable MIC values as low as 0.50 and 3.74 µg/ml against Mycobacterium tuberculosis and Mycobacterium bovis respectively. Several compounds showed potent antimycobacterial activity against both drug-sensitive and drug resistant strains of Mycobacterium tuberculosis. However, the toxicology and mode of action of many of the antimycobacterial compounds documented in the current paper remains unexplored. The in vivo studies and clinical trials are still lagging, making the antimycobacterial research less likely to yield possible antimycobacterial drugs in the pharmaceutical industry, alleviating antimicrobial pressure of the readily available antibiotics within the health sector. However, the in vitro bioactivity of the reported compounds from various medicinal plants serves as a first step towards eradicating various human and animal mycobacterial infections worldwide.