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DOI: 10.1055/s-0039-3399961
Antimycobacterial screening and safety evaluation of Tithonia rotundifolia, a southern Africa alien invasive weed
Publication History
Publication Date:
20 December 2019 (online)
Tuberculosis remains a global threat and a leading cause of mortality. Multidrug-Resistant (MDR) and Extensively-Drug Resistant (XDR) tuberculosis are major challenges, especially in Africa. Considering this, the investigation of medicinal plants as a source of treatment is advocated. Tithonia rotundifolia, an invasive plant with negative ecological impacts in Africa, was screened against non-pathogenic Mycobacterium aurum, M. fortuitum, M. smegmatis and pathogenic M. bovis and M. tuberculosis H37RV. The serial microdilution assay was used to determine antimycobacterial activity of acetone, dichloromethane and hot water extracts of the weed plant. Cytotoxicity of the extracts against African Vero monkey kidney, human colon Caco-2 and C3A liver cells was studied using a tetrazolium-based colorimetric assay while genotoxicity tests were conducted against Salmonella strains TA98 and TA100 using the Ames test. The tested extracts were inhibitory against both the pathogenic and non-pathogenic Mycobacterium strains. Better activity was displayed against the non-pathogenic M. aurum, M. fortuitum and M. smegmatis with minimum inhibitory concentration values ranging between 0.04 and 0.08 mg/ml. Little cytotoxicity of the extracts was noticed with LC50 values against Vero Monkey kidney cells between 0.78 and 0.96 mg/ml (selectivity index, SI = 0.38 to 24.05), Caco-2 between 0.198 and 0.32 mg/ml (SI = 0.05 to 5.84) and C3A between 0.67 and 0.88 mg/ml (SI = 0.29 to 22.56) respectively. No genotoxicity was detected against the Salmonella strains TA98 and TA100. The results from this study motivate further investigation of T. rotundifolia for possible development of effective antimycobacterial treatments.