Anti-mycobacterial activity of five plant species used as traditional medicines in the Western Cape Province (South Africa)

Ethnopharmacological relevanceFive plants used in traditional medicine in the Western Cape Province of South Africa, have been investigated for anti-mycobacterial activity: Olea capensis, Tulbaghia alliacea, Dittrichia graveolens, Leysera gnaphalodes and Buddleja saligna.Aim of the StudyThe aim was to assess antimycobacterial activity in plants used in treatment of symptoms of TB, and through activity-guided fractionation of extracts to isolate compounds or mixtures with potential as anti-TB drug leads.Materials and MethodsExtracts and derived fractions were assayed against strains of Escherichia coli, Staphylococcus aureus, and Mycobacterium aurum A+. Isolated pure compounds were further tested against Mycobacterium species M. avium ATCC 25291, M. scrofulaceum ATCC 19981, M. microti ATCC 19422 and Mtb H37Rv, and for cytotoxicity against Chinese hamster ovarian cells.ResultsExtracts of B. saligna and L. gnaphaloides exhibited significant anti-mycobacterial activity, primarily associated with the presence of non-cytotoxic triterpenoids oleanolic acid in B. saligna and both oleanolic and ursolic acids in L. gnaphaloides.ConclusionsAnti-mycobacterial activity of extracts of selected plants is consistent with their traditional use. The identification of oleanolic and ursolic acids in these plants, and verification of their activity, underlines the potential for exploring structure-activity relationships of derivatives of these ubiquitous triterpenoids.