Essential Oil Variation within Warburgia salutaris-A Coveted Ethnomedicinal Aromatic Tree.

Warburgia salutaris, known as 'Pepper bark', is an ethnomedicinally important tree found in the southern regions of Africa. A total of 75 fresh leaf specimens of W. salutaris (n=40 wild and 35 cultivated) were collected from the Limpopo (wild) and KwaZulu-Natal provinces (cultivated), two distinct locations in South Africa. In this study, the leaf essential oils obtained by hydrodistillation were characterized using gas chromatography coupled to mass spectrometry/flame ionization detection (GC/MS/FID). More than 15 compounds, accounting for 90-99 % of the total oil composition were identified. The analysis revealed that myrcene (0.6-65.3 %), (E)-ß-ocimene (nd-56.9 %), (Z)-ß-ocimene (nd-19.1 %), α-pinene (nd-19.1 %) and limonene (nd-11.7 %) are major constituents of W. salutaris essential oils. Chemometric analysis revealed two major chemotypes within the essential oils with a modeled variation of approximately 60 %. Linalool and germacrene D were revealed as markers associated with the wild-harvested oils, while cultivated oils were distinguished by higher levels of limonene and α-humulene. The intra-population variation indicated two chemically distinct chemotypes from three different populations, however, the season of harvest did not have a direct influence on the chemical profiles of the essential oils.

Bioactivities of Plectranthus ecklonii constituents.

Plectranthus ecklonii Benth. is traditionally used in South Africa for treating stomach aches, nausea, vomiting and meningitis. Bioassay-guided fractionation of the ethyl acetate extract of the plant led to the isolation of two known compounds, parvifloron D and parvifloron F, neither of which has been previously reported for this species. The compounds exhibited minimum inhibitory concentrations of 15.6 and 31.2 microg/mL, respectively against Listeria monocytogenes, whereas the values against a drug-sensitive strain of Mycobacterium tuberculosis were 190 and 95 microg/mL, respectively. The ethyl acetate extract of P. ecklonii and its isolated compounds were tested for their activity on tyrosinase inhibition. The concentration at which half the tyrosinase activity was inhibited (IC50) by the extract was found to be 61.7 +/- 2.7 microg/mL. The antibacterial activity of the extract and its isolated compounds correlates with the traditional use of the plant for various ailments such as stomach aches, diarrhea and skin diseases. The fifty percent inhibitory concentrations of parvifloron D and parvifloron F against vero cell lines were found to be 2.9 microg/mL and 1.6 microg/mL, respectively. This is the first report of the bioactivity of P. ecklonii extract and its constituents.