Past and present postgraduate students


| MSc Med | 2001 -2003
The antimicrobial properties and chemical composition of leaf essential oils of selected indigenous Lamiaceae species.

Many species belonging to the Lamiaceae (mint family) are used extensively in traditional healing. Indigenous Lamiaceae species such as Ballota africana, Leonotis loenurus and Salvia runcinata have a distinct common aromatic property. Although many members of the Lamiaceae such as lavender and rosemary have become household names with proven antibacterial properties, the South African representatives of this family of plants remain largely unexplored. South Africa has a cultural diversity with traditional healing being
integral to each ethnic group. Indigenous medicinal plant use is well recorded in the readily available local ethnobotanical literature. Despite the well-documented ethnobotanical data, very little scientific information is available on our indigenous medicinal plants. A concerted and organised effort is required to explore the chemistry and biological activity of our indigenous medicinal plants with the aim of finding a scientific rationale for the many "muthi medicines” used by the people of South Africa. Given the current problem with the development of bacterial resistance there is a great urge to discover new potent antibiotics. Worldwide spending on finding new anti-infective agents is expected to increase 60% from the spending levels in 1993, and it is predicted that phytochemicals will find their way into the arsenal of antimicrobial drugs prescribed by physicians. Many plants have been reported to be used in the treatment of cuts, wounds, sores, ear infections etc. indicating possible antimicrobial properties. Due to the known antimicrobial properties of essential oils, an interest has developed in aromatic plants in general, in the continued search for new natural molecules to be used in phytopharmaceuticals.

Ten Lamiaceae species commonly found in South Africa were selected and leaf material collected. The leaves were hydro-distilled to extract the essential oils. The oils were analysed by gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS). Antimicrobial assays incorporating four bacteria, two yeasts and one fungus were performed on the essential oils.

Species that were active against either the bacteria or the yeasts or the mould.

Species

Klebsiella pneumonia

Pseudomonas aeruginosa

Cryptocossus neoformans

Candida albicans

Aspergillus niger

Hemizygia
modesta

Inactive

Active

Active

Inactive


Inactive

Mentha
longifolia

Active

Inactive

Active

Active

Inactive

Ocimum
americanum

Inactive

Inactive

Active

Inactive

Slightly
active

Salvia
africana-lutea

Inactive

Active

 Inactive

Active


Active

Salvia
disermas

Inactive

Inactive

Active

Active

Inactive

Salvia
namaensis

Active

Inactive

Inactive

Active

Inactive

Salvia
runcinata

Active

Inactive

Active

Active


Active

      
Seven of the ten oils that were tested showed some antimicrobial activity. The antimicrobial activities of the oils were shown to differ depending on the type of compounds found within the essential oil. Results from previous studies implicate compounds such as linalool, terpenin-4-ol and carvone to possibly contribute to the antimicrobial properties exhibited by some of the active species in this study.

Principal supervisor: Prof AM Viljoen
Co-supervisor: Dr SF van Vuuren (WITS)



Hemizygia transvaalensis | Lamiaceae | flowers | botanical - Kirstenbosch, Cape Town, South Western Cape, South Africa [2008 © alvaroviljoen.com]