The genus Pteronia consists of approximately 80 species which are widely distributed in southern Africa. For hundreds of years the indigenous people of southern Africa have turned to the earth in order to provide healing for their people. The genus Pteronia has been amongst the first species to be used by the San and Khoi-San people for treating infections and stomach ailments.
Ten species were selected for the purpose of this report. The essential oils were isolated by using a Clevenger-type apparatus while the non-volatiles were extracted with acetone and methanol. The essential oils and extracts were assessed for antimicrobial activity. The disc diffusion assays included three Gram-negative bacteria; Escherichia coli, Yersinia enterocolitica and Klebsiella pneumoniae, three Gram-positive bacteria; Staphylococcus aureus, Bacillus subtilis and Bacillus cereus as well as one yeast; Candida albicans. Results indicated that the species were primarily active against Gram-positive organisms. The minimum inhibitory concentration of the ten most active species (essential oils and extracts) were determined using the microdilution method. The most promising activity was noted for P. fasiculata which had a MIC of 0.22 mg/ml against S. aureus, 0.39 mg/ml against B. cereus and 2.08 mg/ml against B. subtilis. The essential oils analysis by GC/MS revealed two chemotypes. In Pteronia pallens, P. empetrifolia and P. flexicaulis rare compounds, such as presilphiperfolol-7-ene, 7-α-(H)-silphiperfol-5-ene, 7-β-(H)-silphiperfol-5-ene, α-campholene aldehyde, silphiperfol-5-ene, camaroonan-7-α-ol, silphiperfol-7-β-ol, presilphiperfolan-9-α-ol and presilphiperfolan-8-ol (a major compound in Pteronia pallens) were recorded.
A cluster analysis of the essential oil data indicated that individual collections of P. camphorata within a population were tightly clustered. Similarly, P. pallens sampled from three different localities were also united in the cluster analysis. These results suggest minimal within and between population variations for some of the species studied.
Principal supervisor: Prof AM Viljoen
Co-supervisor: Dr SF van Vuuren (WITS)