Background: Tuberculosis (TB) is still a global health problem mainly due to development of resistance and co-infection\nwith the Human immune Virus (HIV). Treatment of multi and extensively drug resistant TB requires use of second line\ndrugs which are less efficacious, expensive and very toxic. This has necessitated a need to search for new treatment\nregimens especially from medicinal plants. Zanthoxylum leprieurii, a plant species from Rutaceae is used locally in the\ntreatment of tuberculosis in Uganda. The aim of the study was to isolate, identify and characterize bio active compounds\nfrom Z. leprieurii stem bark with antimycobacterial activity.\nMethods: Crude extracts, fractions and compounds from air dried stem bark of Z. leprieurii were tested against pan\nsensitive (H37rv), isoniazid resistant (TMC 301) and rifampicin resistant (TMC 331) strains of M. tuberculosis using micro\nplate alamar blue assay. Isolation of active compounds was done by using column chromatography and thin layer\nchromatography. They were analysed using nuclear magnetic resonance spectroscopy and mass spectroscopy.\nResults: The methanol extract had minimum inhibitory concentrations (MIC) of 47.5, 75.3 and 125.0 �¼g/ml on the pan\nsensitive strain, rifampicin resistant and isozianid resistant strains of M. tuberculosis respectively. The chloroform extract had\nMIC values of 260 �¼g/ml agnaist the pan sensitive strain and 156 �¼g/ml on the rifampicin resistant strain. Of the sixteen\nfractions from the methanol extract, fraction Za4 (MIC = 6.3 �¼g/mL, 23.0 �¼g/mL, 11.7 �¼g/mL) and Za6 (MIC = 11.7 �¼g/mL\n31.2 �¼g/ml, 31.2 �¼g/ml) were the most active. Three acridone alkaloids; hydroxy-1, 3-dimethoxy-10-methyl-9-acridone (1),\n1-hydroxy-3-methoxy-10-methyl-9-acridone (2) and 3-hydroxy-1, 5, 6-trimethoxy-9-acridone (3) were isolated from Za4\nand Za6. TheMIC of compound 3 was found to be 5.1 �¼g/ml, 4.5 �¼g/ml and 3.9 �¼g/ml on H37rv, TMC 331 and TMC 301\nwhile that of 1 was found to be 1.5 �¼g/ml, 8.3 �¼g/ml and 3.5 �¼g/ml respectively.\nConclusion: The results of this study suggest that Z. leprieurii is active on resistant strains of M. tuberculosis and could be a\npotential source of new leads against resistant tuberculosis. It also verifies the local use of the plant in treatment of\ntuberculosis.
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