Anti-mycobacterial, cytotoxicity and genotoxicity effects of five traditionally used anti-tuberculosis plants in South Africa
24 October 2017 (online)
Tuberculosis (TB) is a re-emerging bacterial infectious disease that infects both humans and animals (cattle). This disease has caused major health concerns and is responsible for about 1.4 million deaths per annum. TB can be cured, however, the emergence of drug-resistant strains has made the disease difficult to treat, thus establishing a need to search for new effective agents. Worldwide, plants are believed to serve as anti-TB agents. In South Africa, there is potential to find plants with anti-TB effects due to the great floral diversity found in this region. Based on a local ethnobotanical survey identifying 24 traditionally used anti-TB plants, and after scrutiny of available literature, Hypoxis colchicifolia, Heteromorpha trifoliata, Phymaspermum acerosum, Pterocelastrus echinatus and Pittosporum viridiflorum were selected for antimycobacterial activity. Acetone, 70% ethanol, cold and hot water extracts were tested for antimycobacterial activity against non-pathogenic Mycobacterium aurum, M. bovis BCG, M. fortuitum, M. gordonae and M. smegmatis. Extracts that demonstrated MIC values less than 1 mg/ml against at least three Mycobacterium strains were evaluated for cytotoxicity (againts Vero monkey kidney cells) and genotoxicity (against Salmonella typhimurium TA98 and TA100). The MIC values ranged from 0.020 to 2.500 mg/ml, and LC50 values ranged from 0.001 to 17.739 mg/ml. P. acerosum ethanol extract demonstrated the best MIC value of 0.020 mg/ml against M. smegmatis and M. bovis, whereas P. echinatus acetone extract was the most cytotoxic (LC50= 0.001 mg/ml). Almost all tested extracts were non-genotoxic with the exception of of H. colchicifolia and P. viridiflorum that were slightly genotoxic, as the number of revertant colonies increased with increasing concentrations. The results indicate that these plants could be investigated further against pathogenic and drug-resistant TB strains, which is underway.