Artemisia afra Jacq. Wild also known as African wormwood, ”umhlonyane„ (Xhosa and Zulu), ” lengana„ (Sotho and Tswana) and ”wildeals„ (Afrikaans) is an aromatic shrub belonging to the Asteraceace. It is widespread in South Africa extending from the mountainous regions of the South Western Cape, along the eastern coast to the Northern Province (van Wyk et al., 1997). Due to the popular use of A. afra, herbal tinctures have been prepared for commercial distribution. As the chemotypic variation remains
unrecorded it has been impossible to standardize extracts containing A. afra. The aerial parts of sixteen samples from four natural populations were hydrodistilled and the essential oil analysed by GC-MS and tested for antimicrobial activity on a number of bacteria and fungi. The essential oil composition varied quantitatively and qualitatively within and between natural populations. With the aid of cluster analysis, several chemotypes have been identified based on the presence and quantity of the following compounds; β-thujone (5.55-77.65%), ş-thujone (1.37-57.73%), camphor (1.00-48.99%),
1.8-cineole (2.31-50.09%), artemisia ketone (14.47-27.97%), artemisia alcohol (9.31-27.76%) and santolinyl acetate (4.14-24.32%). The variation did not correlate to geographical distribution. The essential oil of all the plants was active against all organisms studied except Pseudomonas aeruginosa and Enterococcus facaelis. The oil exhibited higher antifungal properties than antibacterial activity. The pure terpene standards of major compounds detected in A. afra (thujone, cineole, camphor etc.) showed no antimicrobial activity and it can be assumed that the oil could exert antimicrobial properties by working in a synergistic way. Artemisia afra varies within and between natural populations and standardizing of commercial products will be problematic without cloning of a favourable chemotype. Selection of favourable chemotypes should be based on efficacy (i.e. wide spectrum anti-microbial activity) and safety index (e.g. low thujone content).
Principal supervisor: Prof AM Viljoen
Co-supervisor: Dr SF van Vuuren (WITS)