Antimicrobial activity and mutagenic effects of twelve traditional medicinal plants used to treat ailments related to the gastro-intestinal tract in South Africa

Petroleum ether, dichloromethane, ethanol (70%) and water extracts of 12 South African plants were screened using microdilution assays against Gram-positive (Bacillus subtilis, Staphylococcus aureus), Gram-negative (Escherichia coli) bacteria, and the fungus Candida albicans. No antimicrobial activity was observed in water extracts. The ethanol extracts of Becium obovatum leaves showed the best antibacterial activity with a minimum inhibitory concentration value of 0.074 mg/ml against B. subtilis. The petroleum ether extract of leaves of Cucumis hirsutus, Haworthia limifolia and Protea simplex showed good antibacterial activity with MIC values ranging between 0.098 and 0.780 mg/ml against all the test bacteria. The petroleum ether extract of P. simplex leaves showed the best anti-candidal activity with a minimum fungicidal concentration value of 0.014 mg/ml. The ethanol extracts of Agapanthus campanulatus (leaves and root), Dissotis princeps and Gladiolus dalenii as well as the dichloromethane extract of P. simplex leaves showed good anti-candidal activity with minimum fungicidal concentration values ranging between 0.037 and 0.39 mg/ml. Mutagenicity tests conducted on extracts that showed good antimicrobial activity suggest the plants are probably safe for consumption. The results obtained in this study show that some of the traditional plants may indeed be effective for the treatment of ailments related to gastro-intestinal disorders that may be due to the test pathogens.