Inventory of the best-selling medicinal plants on the Lubumbashi markets (DR Congo) and authentication of samples from the 3 most popular species.

Ethnopharmacological Relevance: Knowledge of the high-sale medicinal plants and their authentication are essential parameters to ensure the safety of people using herbal medicine and to plan the safeguarding of medicinal species threatened with extinction.

Aims: The present study, carried out in Lubumbashi, Democratic Republic of Congo, aimed to geolocate medicinal plant sales points, list the best-selling species, and authenticate samples of the most popular species on the market.

Methods: A survey was conducted among the medicinal plant sellers in Lubumbashi's markets and other public spaces, to identify the best-selling species. Samples of the species reported as the most sold were purchased for sales unit weight measurement, and authentication. For the 3 most popular plant species, the identity of 92 samples, purchased from some 25 herbalists, was assessed by combining the microscopic characteristics of powdered drugs with the HPTLC fingerprints of methanolic extracts; for each species, these samples were compared with 1 or 2 botanically authenticated reference samples. As abundant starch granules were detected by microscopy, some samples were suspected of heavy flour contamination, which was confirmed by an enzymatic determination of their starch content.

Results: A total of 108 herbalists (48.1 % women) with a median age of 37 years (range, 20-67 years), and a median seniority of 5 years (0.7-30) were interviewed. From a total of 514 purchased samples, 396 (77.0 %) corresponded to 56 species that could be identified, including 92 samples representing the 3 most frequently sold plant species. The identities of 118 samples (having 82 different vernacular names), could not be determined, due to the lack of voucher specimen. Roots were the most sold organ (56.0 %; n = 514), mainly in powder form (78.7 %), and the median price was 21 USD/kg, at the time of the survey (January to May 2021). The identified specimens were, predominantly, the roots of Terminalia mollis M.A.Lawson (33.3 %), Securidaca longepedunculata Fresen (28.7 %), and stem barks of Nauclea pobeguinii Hua ex Pobég. (23.1 %); from the recorded sales figures, the amounts of material annually sold for these 3 species are estimated at about 5.7, 6.0, and 3.1 tons, respectively. Some sellers reported problems in identifying and/or preserving S. longepedonculata and T. mollis. Among the 92 samples analyzed for the three species, 18.5 % raised problems, including species substitutions (14/17), dilution with flour (1/17), dilution with flour and species substitution (1/17), and detection of a phytochemical variant (1/17), that could arise either from contamination by another species, a particular plant growth environment, or poor storage conditions.

Conclusion: The confusion/adulteration rate measured here for highly popular species is quite alarming (18.5 %); but, indeed, roots, especially as powders, are often difficult to differentiate based on the coarse organoleptic examination practiced by herbal traders. Microscopic and phytochemical characteristics reported in this study, quite easy to obtain with basic laboratory equipment, should be systematically applied by the health products regulatory authorities to control the quality of herbals and ensure that patients get the drug desired for their treatment.