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

Abstract

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)-β-ocimene (nd-56.9 %), (Z)-β-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.