ETD Collection

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    The composition, geographical variation and antimicrobial activity of Mentha longifolia subspecies polyadena (Lamiaceae) leaf essential oils
    (2008-09-26T08:54:38Z) Petkar, Sahir Yusuf
    Mentha longifolia subsp. polyadena was collected from seven localities in South Africa and from a single population in Botswana to study the essential oil composition and antimicrobial activity of this ethnomedicinal plant. The essential oils were obtained by hydrodistillation and analysed by gas chromatography coupled to mass spectroscopy (GC/MS) and a cluster analysis was performed on the essential oil dataset. From eight samples (representing eight natural populations), two major chemotypes were identified: (i) a menthofuran rich type (51.4% - 61.6%); and (ii) a cis-piperitone epoxide (14.7% – 35.7%) and piperitenone oxide (14.6% - 65.7%) rich type. The constituent analysis showed quantitative variation with higher amounts of oxygencontaining monoterpenes ranging from 56.5% to 89.6% whilst the sesquiterpene hydrocarbons ranged from 4.4% to 16.7%. The essential oil from the different localities mostly showed moderate to good antimicrobial activity against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Moraxella catarrhalis, Yersinia enterocolitica and Enterococcus faecalis. The oils were generally inactive against Escherichia coli and Salmonella typhimurium. Candida albicans and Cryptococcus neoformans indicated highest sensitivities for oil samples from Komukwane (3 mg/ml and 0.5 mg/ml respectively) and Prins Albert (0.5 mg/ml and 1.6 mg/ml respectively). The HPLC profiles of the methanol and chloroform (1:1) extracts were more conservative and less variable compared to the essential oils. Two major peaks corresponding to retention times of 22.39 min and 26.47 min were present in all eight samples. Most of the solvent extracts displayed moderate to good antimicrobial activity against Gram-positive pathogens, in particular against S. aureus, S. epidermidis and B. cereus with MIC values ranging from 0.5 mg/ml to 2 mg/ml in most cases. The extracts also demonstrated moderate to good activity against most of the Gram-negative pathogens, in particular against Y. eneterocolitica and M. catarrhalis, with MIC values ranging from 0.5 mg/ml to 2 mg/ml. These results may in part provide scientific evidence for the extensive use of Mentha longifolia in traditional healing.
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    The antimicrobial properties and chemical composition of leaf extracts and essential oils of indigenous Pteronia species
    (2008-06-30T12:07:12Z) Coovadia, Zubair Hoosen
    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.