Extension of the EU 'Traditional Herbal Medicine' concept to an oral transmission context: the case of the 5 anti-infectious medicinal plants most widely used in Burundi

Introduction: In Burundi, five plants, namely Urtica massaica Mildbr., Mikania natalensis DC., Senecio maranguensis O. Hoffm., Justicia nyassana Lindau and Helichrysum congolanum Schltr. & O. Foffm., are widely cited for the treatment of "diseases compatible with a microbial infection" i.e. probably infectious diseases. In view to derive a regional concept of plausible activity and safety, akin to the European Union notion of "Traditional Herbal Medicine", the present work aims to compare the local knowledge and uses of these five popular anti-infectious plants, including eventual recommendations and interdicts.

Materials and Methods: A survey was carried out among 43 traditional healers from different regions of Burundi, including the city of Bujumbura, to fully repertory the uses of these five medicinal plants and define consensus in their uses through their fidelity levels and use values for each cited disease. Phytochemical analyses of these plants allowed to identify their main classes of secondary metabolites.

Results: From their fidelity levels, the studied plants appear extensively reported for infectious diseases, except for U. massaica, that is mainly used in inflammatory conditions.
M. natalensis has the highest use value for the treatment of skin diseases (use value, 1.65), digestive tract disorders (1.07) and gastrointestinal infections (0.51); U. massaica for inflammation (1.07), digestive tract (0.51) and metabolic disorders (0.42); J. nyassana for gastrointestinal infections (2.00), skin diseases (0.81) and circulatory system disorders (0.51); S. maranguensis (2.60) and H. congolanum (2.49) for skin diseases.

Conclusions: Interviews are a quite interesting survey method to apprehend usages of herbal drugs, but the information on their efficacy, side effects and interdicts is particularly difficult to obtain. In the absence of clinical trial data, the marked convergence of some usages nevertheless indicates a plausibility of efficacy and safety, coherent with the EU concept of "Traditional Herbal Medicine", which point to possible rational recommendations of treatments. There however remains a need for a strategy to obtain reliable safety information and to legally define whether a given use can be considered as "traditional".