Characterization of intracellular activity of antitubercular constituents from the roots of Euclea natalensis

Naphthoquinones and triterpenes isolated from the roots of Euclea natalensis A.DC (Ebenaceae) were evaluated for their inhibitory activity against Mycobacterium tuberculosis. Crude extract, diospyrin and 7-methyljuglone isolated from the plant, exhibited minimum inhibitory concentrations of 8.0, 8.0, and 0.5 μg ml-1, respectively, against M. tuberculosis H37 Rv (ATCC 27294), a drug-sensitive strain. Minimum inhibitory concentrations (MICs) of 7-methyljuglone against a panel of clinical pan-sensitive and drug-resistant strains of M. tuberculosis ranged from 0.32 to 1.25 μg/ml. The concentration of 7-methyljuglone that effected a 90% reduction of growth of M. tuberculosis Erdman within J774.1 macrophages was 0.57 μg/ml. The superior intracellular and extracellular inhibition of M. tuberculosis by 7-methyljuglone relative to that of the antituberculosis drugs streptomycin and ethambutol suggests that this compound be considered as a lead for further investigations. © 2005 Taylor & Francis Ltd.