25 - Xysmalobium undulatum

Abstract

Xysmalobium undulatum (L.) Aiton commonly known as ‘uzara’, is widely distributed in many countries in southern Africa. This robust annual herb can grow up to 1m high from a perennial rootstock, and has thick and erect hairy branches. The plant has a strong flowering stem arising from a branched fleshy root. The leaves are arranged in opposite pairs, and discharge a milky latex. The dried roots are characterised by a pale brown exterior and white interior, with a very distinct musty smell. Traditionally, the plant is used by various local ethnic groups to treat a broad range of diseases. In South Africa, a decoction prepared from the roots is used as a stomach carminative and diarrhoea remedy. Dried root powder has been reported to be used for wound healing, treatment of sores and abscesses. The root extracts contain various cardenolide cardiac glycosides, the major compounds of interest being uzarin and xysmalorin. Methanol extracts of six root samples were analysed by high-performance thin-layer chromatography (HPTLC). The consistent profile between the six samples suggests that the chemistry is conserved. The marker compound uzarin was identified in all six samples. An ultra-performance liquid chromatography coupled to mass spectrometry and photodiode array detection (UPLC-MS-PDA) method was developed to profile the root extracts. Uzarin, and its structural analogue xysmalorin, were adequately separated and identified in all extracts. In view of toxicity concerns associated with the cardiac glycosides, these methods may be of value in the qualitative and quantitative quality control of uzara.