Abstract
BackgroundTuberculosis is a world-wide problem affecting humans and animals. There is increasing development of resistance of the pathogens to current antimycobacterial agents. Many authors have investigated activities of extracts and isolated compounds from plants. The traditional uses of plants have frequently been the criterion to select plants investigated. In this contribution, we investigate whether plant extracts with very good activity against Escherichia coli may also be active against mycobacteria.MethodsThe antimycobacterial activity of eight South African tree leaf extracts with high activity against Escherichia coli were determined in vitro against Mycobacterium smegmatis, M. fortuitum and M. aurum, using a serial microdilution method. The cellular cytotoxicity was also determined by the MTT assay using Vero monkey kidney cells. The selectivity index was determined by dividing the cytotoxicity of extracts by MIC.ResultsThe antimycobacterial activity of the extracts ranged from 0.02 to 2.5 mg/ml. Mycobacterium smegmatis was more sensitive to the extracts (Average MIC = 0.96 mg/ml) and Mycobacterium aurum was comparatively resistant (Average MIC = 2.04 mg/ml). The extracts of Cremaspora triflora had strong antimycobacterial activity with a MIC of 0.05 mg/ml that compared reasonably well with that of streptomycin (0.01 mg/ml) and rifampicin (0.03 mg/ml), p > 0.05. Cremaspora triflora had the best selectivity index of 2.87 against Mycobacterium fortuitum.ConclusionThe high activity of C. triflora extracts against the fast-growing mycobacteria and good cellular safety is promising. It may be interesting to investigate extracts against pathogenic M. tuberculosis, M. bovis and M. avium cultures and to isolate active antimycobacterial compounds.
Highlights
Tuberculosis is a world-wide problem affecting humans and animals
There are several reasons given to justify the constant search for new anti-TB drugs to improve the current treatment regimen by reducing therapy time and addressing drug resistance especially against multi-drug resistant (MDR) and extreme drug resistant (XDR) mycobacterial strains
The choice of using fast growing and non-pathogenic Mycobacterium spp. in antimycobacterial assays was based on their avirulent nature and similarity in sensitivity to pathogenic Mycobacterium strains [14, 15]
Summary
Tuberculosis is a world-wide problem affecting humans and animals. There is increasing development of resistance of the pathogens to current antimycobacterial agents. Many authors have investigated activities of extracts and isolated compounds from plants. The traditional uses of plants have frequently been the criterion to select plants investigated. In this contribution, we investigate whether plant extracts with very good activity against Escherichia coli may be active against mycobacteria. An estimated 5–15% of the 2–3 billion people exposed to M. tuberculosis will develop the disease in their lifetime. The probability is even higher among people infected with HIV [1, 2]. It has been shown that extracts of Maerua edulis, Securidaca longipedunculata, Zanthoxylum capense and Tabernaemontana elegans have high activity against Mycobacteria spp. It has been shown that extracts of Maerua edulis, Securidaca longipedunculata, Zanthoxylum capense and Tabernaemontana elegans have high activity against Mycobacteria spp. [4, 5]
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