Abstract
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
