In vitro inhibition of Mycobacteria by Rwandese medicinal plants

A series of 15 Rwandese medicinal plants used by traditional healers to treat pulmonary diseases were screened for anti-Mycobacterium tuberculosis activity. Three plant extracts showed activity at 1000 μg/mL: Bidens pilosa (leaves), Pentas longiflora (roots) and Tetradenia riparia (leaves). These plant extracts were studied further against several mycobacterial species: M. tuberculosis, M. avium complex, M. simiae and a new simiae like Mycobacterium species (SLM). None of the plant extracts showed activity against M. avium and SLM at 1000 μg/mL. M. simiae was sensitive to T. riparia and P. longiflora extracts (1000 μg/mL) and M. tuberculosis towards T. riparia (500 μg/mL) and B. pilosa (100 μg/mL). The active principle of T. riparia, 8(14), 15-sandaracopimaradiene-7α, 18-diol, was also evaluated for its antimycobacterial activity and the concentration required for inhibiting M. tuberculosis ranged from 25 μg/mL to 100 μg/mL. The extract of the leaves of T. riparia can be used as a differentiation test (at 1000 μg/mL in the medium) for M. simiae and SLM.