24 - Warburgia salutaris

Abstract

Warburgia salutaris (G. Bertol.f.) Chiov. (Canellaceae) is an endangered, medicinal tree distributed in a few locations in South Africa, Swaziland, Zimbabwe, Mozambique, Malawi and Zambia. The bitter, peppery-taste of the stem bark has earned W. salutaris the name ‘pepper bark tree’. Ethnomedicinally, the important part of the tree is the bark, which is used in the treatment of respiratory tract infections, gastrointestinal ailments, pain, inflammation and skin conditions. Owing to its widespread traditional use, a range of in vivo and in vitro bioactivities has been investigated including antimicrobial, antiparasitic, anti-inflammatory, anti-oxidant and anticancer activities. Warbugia salutaris is commercially available in crude form, as an essential oil and other dosage forms in over-the-counter products. As an indigenous commercial plant, the quality control of W. salutaris is of paramount importance hence, the current protocol on the chemical profiling of the raw material is presented. The bark and the aerial parts were analysed using high-performance thin-layer chromatography (HPTLC), ultra-performance liquid chromatography, coupled to mass spectrometry and photodiode array detection (UPLC-MS-PDA), and gas chromatography coupled to mass spectrometry (GC–MS). The essential oils were hydrodistilled from the aerial parts and the non-volatile fractions were extracted from the leaf and bark using methanol. The essential oils viewed under white light, following derivatisation with anisaldehyde, revealed myrcene as the major compound in the HPTLC profiles. The GC–MS chromatograms showed oil profiles consisting of myrcene, Z-β-ocimene and E-β-ocimene as the major constituents. The non-volatile fraction of the bark showed polygodial as the marker compound in all the samples using HPTLC, however, this compound was absent in the leaf profiles. The UPLC-MS-PDA chromatograms of the bark confirmed the presence of polygodial and four additional compounds namely: ugandensidial, cinnamolide-3β-acetate, bemadienolide and cinnamolide.