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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/5693 |
| Date | 26 September 2008 |
| Creators | Petkar, Sahir Yusuf |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf |
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