Medicinal plants used in the treatment of tuberculosis - Ethnobotanical and ethnopharmacological approaches

Tuberculosis is a highly infectious disease declared a global health emergency by the World Health Organization, with approximately one third of the world's population being latently infected with Mycobacterium tuberculosis. Tuberculosis treatment consists in an intensive phase and a continuation phase. Unfortunately, the appearance of multi drug-resistant tuberculosis, mainly due to low adherence to prescribed therapies or inefficient healthcare structures, requires at least 20 months of treatment with second-line, more toxic and less efficient drugs, i.e., capreomycin, kanamycin, amikacin and fluoroquinolones. Therefore, there exists an urgent need for discovery and development of new drugs to reduce the global burden of this disease, including the multi-drug-resistant tuberculosis. To this end, many plant species, as well as marine organisms and fungi have been and continue to be used in various traditional healing systems around the world to treat tuberculosis, thus representing a nearly unlimited source of active ingredients. Besides their antimycobacterial activity, natural products can be useful in adjuvant therapy to improve the efficacy of conventional antimycobacterial therapies, to decrease their adverse effects and to reverse mycobacterial multi-drug resistance due to the genetic plasticity and environmental adaptability of Mycobacterium. However, even if some natural products have still been investigated in preclinical and clinical studies, the validation of their efficacy and safety as antituberculosis agents is far from being reached, and, therefore, according to an evidence-based approach, more high-level randomized clinical trials are urgently needed.