Validating the antimicrobial activity of African traditional medicines – Reflecting on a decade of research

Abstract

Unique and diverse botanical resources make traditional healing an integral part of the African cultural heritage. Plants have been used for centuries as anti-infective agents and the need to validate the traditional use in the last decade is addressed with respect to past challenges, latest developments and future recommendations. Microbiological methods (disc diffusion, minimum inhibitory concentration, time-kill and interactive assays) will be reviewed with practical examples given from some of the most widely used indigenous African medicinal plants. An extensive review of Artemisia afra will be given, encompassing antimicrobial screening, geographical variation, major compound analysis, comparison with commercial essential oils and the use in combination with other plants. Furthermore, the potential use in formulations is demonstrated where preservative efficacies within a cream formulation indicated bactericidal activity against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Pathogen specific studies will be presented where some of the most commonly used plants to treat sexually transmitted infections demonstrate activities as low as 0.2mg/ml (Hypericum aethiopicum and Polygala fruticosa, tested against Gardnerella vaginalis). Also, the five most active plants tested against anti-diarrhoeal pathogens in the remote area of northern Maputaland include Psiduim guajava and Garcinia livingstonei (MIC values of 0.01 and 0.08mg/ml respectively against Bacillus cereus), Gymnosporia senegalensis and Syzygium cordatum (0.13mg/ml against Enterococcus faecalis) and Sclerocarya birea (0.13mg/ml against Proteus vulgaris, Salmonella typhimurium, Shigella flexneri and Staphylococcus aureus). These antimicrobial studies play an important role in the understanding of traditional healing and advancing the phytotherapeutic application of medicinal plants.