Evaluation of the Antimicrobial Effect of the Extracts of the Pods of Piliostigma thonningii (Schumach.) Milne-Redh. (Fabaceae)

Plants have been used traditionally by people in treating and the management of diseases since time immemorial. Traditional medicines including the herbal medicines are used for primary healthcare in some domains in almost every country. Approximately 80% of the population in developing coutries depend on plants as their source of medicine for combating diseases. New and effective antimicrobial agents that have novel mechanism of actions are required. Piliostigma thonningii (Schumach.) Milne-Redh. is a species of flowering plants in the legume family, Fabaceae. Different parts of the P. thonningii plants such as the roots, leaves, seeds, and fruits have been used in treating wounds, heart pain, and gingivitis and as cough remedy. This study focused on determining the antimicrobial properties found in the pods of P. thonningii. The sample was prepared by grinding the dried pods into a fine powder. Successive extraction and extraction with 1 : 1 DCM: methanol was used. The antimicrobial assay was carried out using the broth microdilution and MTT assay. The microorganism used for the tests was Pseudomonas aeruginosa, Candida krusei and Mycobacterium smegmatis. The most potent extract was then used to determine its effect on microbial cell membrane integrity. The results showed that methanol extract had the highest percentage yield of 5%. The extract with the highest antimicrobial effects was ethanol extract with the 100 μg/mL concentration inhibiting the growth of cells to 26%, 87%, and 90% for P. aeruginosa, M. smegmatis, and C. krusei, respectively. The ethanol extracts caused significant leakage of proteins in these microorganisms. In conclusion, the pods of P. thonningii contain phytochemicals with antimicrobial properties. The pods of the plant can be a source of phytochemicals that can serve as sources of lead compounds with antimicrobial effects. One of the mechanisms of action of these phytochemicals is via membrane-damaging effects on microbes.