Study of the anti-mycobacterial and cytotoxicity of medicinal plants used in traditional treatment of tuberculosis in northern Mexico

Tuberculosis (TB) is a global public health threat. Many medicinal plants used in the traditional treatment of TB and other respiratory illness by Tarahumara and other indigenous ethnic groups in Mexico. There is high scientific interest in testing medicinal plants due to increasing drug resistance. Investigation of plants used in traditional medicine for many centuries may be more efficient than blind screening of plants without any ethnomedical context. The major study goal was to  investigate the in-vitro anti-mycobacterial activity and cytotoxicity of extracts from three plants used in the traditional treatment of TB and other respiratory infections in Mexico (L. porteri, A. adstringens, P. canescens). The results revealed that all three extracts had significant inhibitory action against M. tuberculosis at lowest concentration tested in main study (5 µg/ml) and appeared to have relatively low cytotoxicity at low concentrations in 0-50 µg/mL range. The L. porteri plant used by the Tarahumara to treat TB exhibited a MIC50 that was roughly half of that of other plants. The L. porteri extract also exhibited low cytoxicity and had a Therapeutic Index (TI) that was > 10 which suggests it has potential therapeutic value. The results suggest that future studies should investigate the molecular mechanism for observed anti-mycobacterial activity and cytotoxicity of L. porteri. The anti-mycobacterial of A. adstringens was not as robust as the other two plants but its low cytotoxicity and promising TI warrant further study.