Ethnobotany, toxicity and antibacterial activity of medicinal plants used in the Maseru District of Lesotho for the treatment of selected infectious diseases

Abstract Treatment of diseases is a major challenge in Lesotho due to several factors, such as limited availability and affordability of western medicine, as well as accessibility to healthcare facilities. As a result, traditional medicine plays a vital role in the well-being of the population in the country. Many studies conducted on medicinal plants in Lesotho have primarily focused on indigenous uses of the plants. However, the therapeutic potential and safety of a majority of these plants are still unknown. The aim of the study was therefore to evaluate the antibacterial activity and toxicity of plants used in the Maseru District, Lesotho, to treat tuberculosis (35 species), other respiratory tract infections (RTIs) (31 species), gastrointestinal conditions (13 species) and skin ailments (13 species), using the minimum inhibition concentration (MIC) micro-titre plate dilution assay. The antibacterial activity for at large proportion of plant species are reported here for the first time, which may mean that their medicinal use is only limited to the Basotho people. Several plant species demonstrated noteworthy (≤ 0.16 mg/ml) or moderate (> 0.16 and ≤ 1.00 mg/ml) antibacterial activity with Ipomoea oblongata demonstrating the highest antibacterial activity (0.09 mg/ml) against B. cereus. Of the plants that showed noteworthy to moderate activity, Eragrostis curvula, Gerbera piloselloides, Ipomoea oblongata, Metalasia muricata and Thesium costatum had previously not been tested for toxicity levels. The highest levels of toxicity were observed for G. piloselloides, I. oblongata, Senecio asperulus and Withania somnifera. The antibacterial results support to some extent, the traditional Lesotho utilization of previously unstudied plant species for the treatment of some bacterial infections.