Prota 11(2): Medicinal plants/Plantes médicinales 2
Hort. kew., ed. 2, 2: 79 (1811).
Asclepiadaceae (APG: Apocynaceae)
Uzara, milk bush (En).
Origin and geographic distribution
Xysmalobium undulatum occurs in Kenya, Tanzania, Malawi, Zambia, Angola, Namibia, Botswana, Zimbabwe, Mozambique, Lesotho, Swaziland and South Africa.
The bitter fleshy root is one of the most widely used medicinal plants in southern Africa, especially South Africa, and is traded under the name ‘uzara’. In Europe, especially Germany, extracts of the roots have been marketed as ‘uzarae radix’ since the early 1900s to treat acute diarrhoea and menstrual cramps. The daily dose should not exceed 90 mg total glycosides, calculated as uzarin, but poisoning is unlikely when taken orally as the glycosides are poorly absorbed. Because of its excellent tolerability, it can be safely given to young children. In South Africa the roots are sometimes mixed with those of Pachycarpus schinzianus (Schltr.) N.E.Br. as they have the same medicinal uses for intestinal problems.
Throughout southern Africa a decoction or maceration of the pulverized root is taken to treat diarrhoea, dysentery, colic, stomach-ache, cough, food poisoning, syphilis, dysmenorrhoea, infections of the urinary tract and menstrual and afterbirth cramps. It is also taken as a tonic, diuretic and emetic and to treat heart failure. A flower or seed decoction is taken to treat colic as well. Pulverized root is used as snuff to treat headache and hysteria, as a sedative. The latex, plant decoction or powdered root is a popular treatment of wounds and sores, and is also applied to snakebites. In Namibia the latex is applied to warts, skin rash and corns.
In Kenya a root decoction is taken to treat headache. In Zambia a root decoction is taken to treat malaria, typhoid and other fevers, as it produces profuse sweating. In Zimbabwe pulverized root in porridge is eaten as an aphrodisiac. In South Africa the powdered root is sprinkled on skins and hides to prevent dogs gnawing on them. A cold water extract is applied to skin diseases of cattle.
In South Africa the Sotho people eat the cooked young leaves as spinach or mixed in porridge. In southern Africa the floss is used for stuffing mattresses and pillows. The plant enters into religious rituals to divert storms, prevent poisoning and to make dogs keen hunters.
Production and international trade
The dried root is traded internationally as 50% ethanol extracts and as tablets, but the current extent of the trade is unknown.
The roots contain a mixture of cardiac glycosides (cardenolides) called uzarone or xysmalobin. The main compounds are uzarin (5.6%), xysmalorin (1.5%) and their isomers allo-uzarin (0.4%) and allo-xysmalorin (0.1%). Minor compounds include uzarigenin, ascleposide, coroglaucigenin, coroglaucigenin-3-O-β-glucoside, xysmalogenin and pachygenol. From the seeds the glycoside frugoside (0.5%) was isolated.
Uzarin and xysmalorin inhibit motility in the small intestine and urogenital tract, and high doses have a cardiotonic effect, but they are less toxic than digitoxigenin, an isomer of uzarigenin (the aglycone of uzarin).
Ethanolic leaf and root extracts exhibited weak CNS depressant activity in the GABAA-benzodiazepine receptor assay. Aqueous and ethanol extract of both aerial parts and roots showed significant antidepressant activity by exhibiting high affinity to the serotonin transport protein (SERT), in an in-vitro serotonin transport protein binding assay. In a further assay ethanolic extracts showed antidepressant-like effects in one of three animal models.
A methanol extract of the whole plant did not show antiplasmodial activity in vitro. Different root extracts did not show significant antibacterial and antifungal activity in vitro. Methanol and dichloromethane extract of the leaves did not show antimutagenic activity in vitro.
Robust annual herb up to 1 m high, from a perennial rootstock, with thick, erect, hairy branches; roots forming a fleshy, carrot-like root, white inside, with nauseating smell; latex present in all parts. Leaves opposite, simple and entire, undulating; petiole 1–6 mm long; blade lanceolate to oblong, 5.5–22 cm × 1–2.5 cm, base cuneate, apex acute, mucronate, short-hairy on both sides, margins slightly thickened. Inflorescences an axillary or terminal umbel, up to 25-flowered, often clustered at the top of the stem; peduncle 0.5–1 cm long, short-hairy; bracts linear-lanceolate. Flowers bisexual, regular, 5-merous; pedicel 3–12 mm long, short-hairy; sepals lanceolate, 2–5 mm long, acute, pale yellow, softly hairy; corolla campanulate, white, yellowish or greenish inside, outside often purple, lobes triangular, 3–5 mm × 2–3 mm, acute, apex reflexed, glabrous outside, densely white-hairy within at apex and margins; corona lobes attached at base of staminal column, fleshy, broadly ovate to rhomboid, flattened, shorter than the column, with thick obtuse keel, staminal column c. 2.5 mm long, furrowed, appendages broadly ovate; ovary superior, carpels 2, free, stigma head rounded. Fruit usually 1 ovoid follicle, upright through contortion of pedicel, 8–12 cm × 3.5–4 cm, with a short beak, strongly inflated, balloon-like, papery, pale green, sometimes tinged reddish, short-hairy, with soft spiny processes, many-seeded. Seeds ovate, coma 2.5–3 cm long.
Xysmalobium comprises 40–45 species in tropical Africa; about 18 occur in South Africa. It is closely related to Pachycarpus and Gomphocarpus.
Several other Xysmalobium species are medicinally used. Xysmalobium heudelotianum Decne. occurs in savannah throughout tropical Africa. In Benin the pulverized root in water is taken to treat dysentery. In Nigeria the cooked fleshy root is eaten to treat stomach problems and a decoction is taken as a bitter tonic and stomachic. In Gambia the dried root powder mixed with mud is used as a plaster for surfacing the walls of houses, and give protection against vermin. The plant contains cardiac glycosides, which exhibit weak cardiotonic activity. Xysmalobium sessile (Decne.) Decne. occurs in DR Congo, Zambia and Angola. In DR Congo the root is chewed as an aphrodisiac.
Xysmalobium undulatum is common in grassland areas and seasonally wet localities, from sea-level up to 2000 m altitude. Xysmalobium undulatum is self-incompatible. Its flowers are visited by a range of different insects, but only the chafer beetle (Atrichelaphinis tigrina) and pompilid wasps (Hemipepsis) effect pollination.
Transplanting of seedlings needs to be done at an early stage, as the thickened root is deep-rooting. The roots can be harvested when they are 2–3 years old. Roots have been collected from the wild for export to Europe until 1952, after which commercial plantations have been installed in Transvaal, South Africa.
Genetic resources and breeding
Xysmalobium undulatum is not uncommon in most of its distribution area. In South Africa, however, it is officially protected because of overharvesting and habitat destruction. The criteria for selection of material for plantations are not known.
The tubers of Xysmalobium undulatum have interesting traditional uses against acute diarrhoea and standardized preparations are on the market since the early 1900’s. Recent investigations of the tubers and aerial parts against depression give promising results and more research is warranted in order to evaluate its potential as an anti-depressant.
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Correct citation of this article:
Schmelzer, G.H., 2011. Xysmalobium undulatum (L.) W.T. Aiton. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(2): Medicinal plants/Plantes médicinales 2. [CD-Rom]. PROTA, Wageningen, Netherlands.
obtained from SANBI
obtained from SANBI
obtained from SANBI