Chapter Nine - Potential of African flora to combat tuberculosis and drug resistance of Mycobacteria: Rationale classification of antimycobacterial agents from a natural source

This chapter presents a synopsis of African medicinal plants and their derived products with antimycobacterial properties. Several secondary plant metabolites are reported to have anti-tuberculosis activity comparable to existing anti-tuberculosis drugs. Using the data obtained from 77 active plant extracts and 75 active derived molecules towards Mycobacterium tuberculosis H37Rv, the rationale cut-off points for the classification of antimycobacterial agents from natural sources were established. (i) For botanicals: outstanding activity when MIC ≤ 6 µg/mL; excellent activity when 6 2048 µg/mL. (ii) For phytochemicals: outstanding activity when MIC ≤ 2.5 µg/mL, excellent activity when 2.5 512 µg/mL. Importantly, we have identified Artemisia abyssinica Schultz Bip. (Lamiaceae), Diospyros canaliculata De Wildeman (Ebenaceae), Diospyros crassiflora Hien (Ebenaceae), Croton macrostachyus Hochst. ex Del. (Lamiaceae), and Echinops giganteus A. Rich (Asteraceae) as the most active plants, and isobachalcone (1), diospyrone (2), laburnetin (3), 3,4′-di-O-methylellagic acid 3′-O-β-D- xylopyranoside (4), O¹-demethyl-3′,4′-deoxy-psorospermi-3′,4′ diol (5), plumbagin (6), crassiflorone (7), and bafoudiosbulbins C (8), as the most promising antimycobacterial phytochemicals.