In vitro inhibition of drug-resistant and drug-sensitive strains of Mycobacterium tuberculosis by ethnobotanically selected South African plants

Twenty South African medicinal plants used to treat pulmonary diseases were screened for activity against drug-resistant and drug-sensitive strains of Mycobacterium tuberculosis. A preliminary screening of acetone and water p lant extracts against a drug-sensitive strain of Mycobacterium tuberculosis ; H37Rv, was done by the agar plate method. Fourteen of the 20 acetone extr acts showed inhibitory activity at a concentration of 0.5 mg/ml against thi s strain. Acetone as well as water extracts of Cryptocarya latifolia: Eucle a natalensis, Helichrysum melanacme, Nidorella anomala and Thymus vulgaris inhibited the growth of M. tuberculosis. Given the activity of 14 acetone e xtracts at 0.5 mg:ml against the drug-sensitive strain by the agar plate me thod, a further study was done employing a rapid radiometric method to conf irm the inhibitory activity. These active acetone extracts were screened ag ainst the H37Rv strain as well as a strain resistant to the drugs isoniazid and rifampin. The minimal inhibitory concentration of Croton pseudopulchel lus, Ekebergia capensis, Euclea natalensis, Nidorella anomala and Polygala myrtifolia was 0.1 mg/ml against the H37Rv strain by the radiometric method . Extracts of Chenopodium ambrosioides, Ekebergia capensis, Euclea natalens is, Helichrysum melanacme, Nidorella anomala and Polygala myrtifolia were a ctive against the resistant strain at 0.1 mg/ml. Eight plants showed activi ty against both strains at a concentration of 1.0 mg/ml. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.