Antimicrobial activities of four plant species from the Southern Overberg region of South Africa

Four plant species used for medicinal purposes in the Bredasdorp/Elim (Southern Overberg) region of the Western Cape Province in South Africa, were screened for their antimicrobial activity. The antimicrobial activity of aqueous, methanol, ethanol and ethyl-acetate leaf extracts of Bulbine lagopus (Asphodelaceae), Chironia baccifera (Gentianaceae), Conyza scabrida (Asteraceae) and Dodonaea viscosa var. angustifolia (Sapindaceae), were tested against Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Mycobacterium smegmatis. In the disc-diffusion assay, 20 out of the 80 extracts showed activity. Better activity was observed in the liquid dilution assay with all extracts showing a degree of activity. The best activity was observed in the ethanol extract of B. lagopus and the methanol extract of C. scabrida both having an MIC value of 0.3125 mg/ml. In the bioautography, M. smegmatis was chosen as the test organism along with the ethanol, ethyl-acetate and methanol extracts of C. scabrida and D. viscosa var. angustifolia. All six extracts showed at least two zones of inhibition on the TLC plates overlaid with M. smegmatis.