Prota 3: Dyes and tannins/Colorants et tanins
Mem. New York Bot. Gard. 8: 425 (1954).
Caesalpiniaceae (Leguminosae - Caesalpinioideae)
Kantuffa, redwing (En). Mutanda (Sw).
Origin and geographic distribution
Pterolobium stellatum is widespread in Africa, where it is found from Sudan and Eritrea southwards throughout Central, East and southern Africa to South Africa, but not in Angola, Namibia and Botswana. It also occurs in Yemen.
In Ethiopia, since historical times, the infusion of the pounded bark of Pterolobium stellatum, has been a major ingredient for tanning Morocco leather at the same time giving it a bright red colour. It is already mentioned by European travellers in the 19th century. The crushed leaves also yield a dark red dye for leather; ground and boiled in water to which a little oil or butter has been added to help fix the colour, they are also used to dye clothes for mourning, for dark colours in basketry and to colour mats made from doum palm (Hyphaene thebaica (L.) Mart.) leaves. Formerly the leaves were one of the main ingredients for making black ink, based on the chemical reaction of the tannins of the plant with iron slag or iron filings from the blacksmith. This ink is water resistant and was used by the famous plant collector G.W. Schimper around 1840 to write the labels of his Ethiopian plants. Leather is dyed black by treatment with a mixture of dried leaves and iron filings (iron-oxide) in water.
Pterolobium stellatum is also used for firewood and fodder, and as live fence and ornamental. Because of the sharp, recurved prickles, branches are used to make rat traps. Pterolobium stellatum is sometimes planted to combat the weedy cactus Opuntia. In traditional medicine in East Africa, fresh leaves are chewed or a decoction is drunk to treat tuberculosis and related respiratory diseases. In Kenya a root decoction is used by the Maasai against stomach-ache. Juice of the roots is swallowed to treat snakebites. In Malawi a root infusion is drunk by women against infertility.
The leaves of Pterolobium stellatum contain approximately 20% tannin. Neither the tannins of bark and leaves nor their dye content appear to have been investigated and characterized.
Climbing or straggling shrub, with stems up to 15 m long, armed with recurved prickles. Leaves alternate, with small, early caducous stipules, bipinnately compound with 5–13 pairs of pinnae; rachis armed with paired recurved prickles and often also solitary straight ones; leaflets 7–16 pairs per pinna, oblong or elliptical-oblong, 4–12 mm × 2–5 mm, pubescent to glabrous. Inflorescence a dense raceme 5–18 cm long, aggregated into extensive terminal panicles up to 35 cm × 20 cm. Flowers bisexual, slightly zygomorphic, 5-merous, small, sweetly scented, pale yellow or whitish; pedicel 3–6 mm long; sepals 2–3 mm long, unequal, the lower one hood-shaped and embracing the others, pale green; petals almost equal, oblanceolate-oblong, c. 3 mm × 1.5 mm, pubescent towards base; stamens 10, filaments alternately longer and shorter, 4–5 mm long, pubescent below; ovary superior, 1-celled, style gradually enlarged near apex, stigma transverse. Fruit a brick-red to scarlet, ultimately brown, winged pod, with a stalked, 1-seeded basal portion 3–6 cm long and a much prolonged upper suture broadly winged on its lower side; wing 2–4.5 cm × 1–1.5 cm. Seed ovoid-ellipsoid, c. 11 mm × 6.5 mm, olive-green.
Pterolobium belongs to the tribe Caesalpinieae and comprises about 10 species, 9 occurring in Asia and only a single one in Africa.
Pterolobium stellatum is a common shrub, forming thickets in margins and clearings of upland dry evergreen forest, Acacia woodland and riparian formations, mainly at 500–2500 m altitude.
The leaves are mostly collected from the wild, but Pterolobium stellatum is also cultivated and then propagated by seed, cuttings or wildlings. The seeds germinate better when they are scarified mechanically or chemically. They are sensitive to high temperatures, so hot water treatment before germination is not recommended. The seeds can be easily stored in airtight containers for more than a year without loss of viability. Hedges of Pterolobium stellatum plants are impenetrable because of the sharp prickles and can be pruned to a desired height and width.
Genetic resources and breeding
Pterolobium stellatum is widespread and common in many regions, and not in danger of genetic erosion. Germplasm collections are not known to exist, although some companies offer seeds for sale.
Pterolobium stellatum being a widespread multipurpose plant, interesting both as ornamental bush and as impenetrable live fence, could represent a good renewable source of red dye that does not need a mordanting process due to the associated action of tannins. Its medicinal properties are in need of investigation.
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Correct citation of this article:
Jansen, P.C.M., 2005. Pterolobium stellatum (Forssk.) Brenan In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.