Ethnobotanical survey and antimycobacterial activities of plants used against tuberculosis in Lubumbashi, DR Congo.

Abstract

Background: Tuberculosis is still a serious threat to public health in Africa and especially in the Democratic Republic of Congo, which is one of the eight countries with approximately two-thirds of the global cases of tuberculosis. Given the difficulties in accessing health care services and antitubercular treatments, indigenous population also uses plant-based traditional medicine. This study aimed to identify plants with antituberculosis potential in traditional Katangese medicine.

Methods: Interviews were conducted on traditional healers using snowball sampling method. Ethnobotanical data were assessed by determination of the informant consensus factor and the relative frequency of citation. Guided field walks allowed to collect plants. Methanolic extracts were tested on Mycobacterium smegmatis and Mycobacterium bovis BCG using microdilution, diffusion and agar proportion methods. The cytotoxicity of the best extracts was evaluated by cell viability assay on the human cervical squamous carcinoma SiHa cell line. The 50% inhibitory concentration and minimal inhibitory concentration (MIC) were used to determine the selectivity index.

Results: Thirty-eight plant species from 23 families were identified, most of which were from Fabaceae (16%). Eleven out of 17 plant extracts inhibited the growth of M. smegmatis at MIC ranging from 13 to 250 μg/mL. The methanolic extracts of Zanthoxylum chalybeum and Parinari curatellifolia showed MIC₉₉ of 62.5 and 62.5-125 μg/mL, respectively, on M. bovis BCG and showed IC₅₀ values of 28 and 20 μg/mL, respectively suggesting a low selectivity index. This study was the first to investigate the antimycobacterial activity of Terminalia mollis, Phyllanthus muellerianus, Ochna afzelii, and Rothmannia engleriana.

Conclusions: The demonstration of antimycobacterial activity in the plants used in Lubumbashi against tuberculosis opens opportunities for more in-depth research into their chemical composition and toxicity, ultimately aiming to enhance their safety for treatment of tuberculosis.