Brachystegia eurycoma (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Cereal / pulse
Essential oil / exudate
Medicinal
Timber
Fibre
Food security

distribution in Africa (wild)

Brachystegia eurycoma Harms

Protologue: Bot. Jahrb. Syst. 49: 424 (1913).

Family: Caesalpiniaceae (Leguminosae - Caesalpinioideae)

Origin and geographic distribution

Brachystegia eurycoma has a restricted area of distribution, occurring in southern Nigeria and western Cameroon, possibly also in Gabon.

Uses

The wood of Brachystegia eurycoma, known as ‘naga’ or ‘okwen’ in trade, is used for construction, joinery and furniture. It is suitable for flooring, interior trim, interior carpentry, stairs, veneer and plywood.

Traditionally, the bark has been used to make a coarse cloth used as protection against rain and as a shield against arrows. It is used to make containers. The seeds are spicy and consumed as condiment, and are used to prepare a flour, named ‘achi’, used to thicken soups. Igbo people in Nigeria use the plant as anthelmintic.

Production and international trade

The wood of Brachystegia eurycoma is mainly used and traded locally. It may occasionally be exported in mixed consignments.

Properties

The heartwood of Brachystegia eurycoma is pinkish brown with vague bands and rather distant fine streaks, clearly demarcated from the whitish sapwood. The grain is usually interlocked, texture medium.

There is no detailed information on physical and mechanical wood properties of Brachystegia eurycoma, but these are probably comparable to those of Brachystegia cynometroides Harms. The wood should be dried slowly and carefully to avoid defects; end splitting is common. It is hard to work with hand tools and has a blunting effect on saw teeth and cutting edges. To obtain a smooth surface, careful sanding and the use of a filler are required. The nailing and screwing properties are good, but pre-boring is needed to avoid splitting. Reports on the durability of the wood are contradictory; it is mostly considered non-durable, although wood extracts showed insecticidal and fungicidal activities. The heartwood is resistant to treatment with preservatives.

The seed flour used for thickening contains per 100 g: water 10–12 g, fat 13–14 g, protein 10–13 g, dietary fibre 1–2 g, carbohydrate 59–61 g and ash 1.5–4 g. As a thickening agent, 4–20 g of seed flour per litre water is used. Toasting the flour and addition of palm oil increases the viscosity of the solution, while salt has an opposite effect. Several commercial samples of ‘achi’ from Nigeria were found to contain aflatoxin B1-producing strains of the fungi Aspergillus flavus, Aspergillus parasiticus and Aspergillus niger. In a test in Nigeria, the seed mucilage was shown to be suitable as a tablet binder. The fatty acid composition of the seed oil is approximately: palmitic acid 26%, stearic acid 7%, lignoceric acid 13%, linoleic acid 6%, oleic acid 32% (total saturated fatty acids 59%, total unsaturated fatty acids 41%).

Ethanol extracts of the wood, and to a lesser extent aqueous extracts, have shown an insecticidal effect against the termite Amitermes evuncifer and a fungicidal effect against Fomes heterobasidium, Polyporus coridus and Daedalea daedaleopsis; aqueous extracts inhibited the growth and cellulolytic activity of Bacillus subtilis. Aqueous extracts of the bark, and to a lesser extent ethanol extracts, inhibited the growth of several fungi. The root has been tested for its effect on the snail Bulinus globulus, but showed no effect.

Pollen counts in honey samples have indicated that Brachystegia eurycoma is an important bee plant. The yellow or reddish gum exuding from the bark hardens into a gutta-percha-like substance.

Description

• Medium-sized to fairly large tree up to 35 m tall; bole often low-branched and irregular, up to 200(–250) cm in diameter, often with small buttresses; bark surface rough, grey to brown, flaking off in large patches, inner bark hard, fibrous, red, ripple-marked, darkening on exposure, exuding a reddish or yellowish gum; crown widely spreading and flattened, with spreading, twisted branches; twigs hairy but soon becoming glabrous.
• Leaves paripinnately compound with (4–)5(–6) pairs of leaflets; stipules early caducous; petiole 1.5–2.5 cm long, swollen at base, rachis 7–15 cm long; leaflets opposite, sessile, oblong-elliptical, up to 12 cm × 6 cm, basal leaflets smallest, upper ones largest, truncate to rounded and very asymmetrical at base, rounded or slightly notched at apex, thin-leathery, glabrous, pinnately veined with 6–8 pairs of lateral veins.
• Inflorescence a mostly terminal, up to 15 cm long panicle, short-branched, densely brown hairy, many-flowered.
• Flowers bisexual, slightly zygomorphic, small, at base with 2 oblong-obovate bracteoles c. 7 mm long; pedicel very short; sepals 5, c. 3 mm long, slightly unequal, with hairy margins; petals absent; stamens (8–)10, free, c. 9 mm long; ovary superior, ellipsoid, with short stipe, hairy, style slender, coiled.
• Fruit an oblong to oblanceolate or obovate, flattened pod, 12–22 cm × 3.5–6 cm, at a right angle to the stipe, smooth but slightly wrinkled, dehiscent with 2 woody valves, 4–6-seeded.
• Seeds disk-shaped, c. 2 cm in diameter, shiny brown.

Other botanical information

Brachystegia eurycoma flowers in April–May; fruits ripen in September–January. The fruits open explosively, throwing out the seeds. A trial in Nigeria showed that seedlings of Brachystegia eurycoma grow best on a fertile mixture of top-soil and river sand with watering intervals of up to 3 days.

Brachystegia is a taxonomically difficult genus comprising about 30 species, distributed in mainland tropical Africa and South Africa, the majority of species occurring in southern tropical Africa, where they are characteristic of miombo woodland.

Ecology

Brachystegia eurycoma is most common in riverine forest, up to 1150 m altitude. It is locally quite abundant.

Management

In Cameroon the minimum bole diameter allowed for harvesting is 60 cm.

Genetic resources

As Brachystegia eurycoma is fairly common, of high local value for its seed and little exploited as an export timber, it is probably not in danger of genetic erosion, except where its habitat is destructed. Measures to protect the tree as a source of edible seeds and to control its cutting for timber have been proposed.

Prospects

The wood of Brachystegia eurycoma is likely to remain of local importance, but it will remain of little importance for export. The insecticidal and fungicidal activities of the wood deserve more attention. As the seeds are a source of thickener for soups, commercially traded in cities in Nigeria, they will increase in importance. The presence of several aflatoxin-producing Aspergillus species in commercial samples of ‘achi’ warrants further research attention.

Major references

• Agom, D. & Ogar, D., 1994. Report of study on timber extraction in the Ikobi concession area in Afi river forest reserve. Working Paper Cross River State Forestry Project No 3. 15 pp.

• Aubréville, A., 1970. Légumineuses - Césalpinioidées (Leguminosae - Caesalpinioideae). Flore du Cameroun. Volume 9. Muséum National d’Histoire Naturelle, Paris, France. 339 pp.

• Bhat, R. & Karim, A.A., 2009. Exploring the nutritional potential of wild and underutilized legumes. Comprehensive Reviews in Food Science and Food Safety 8: 305–331.

• Keay, R.W.J., 1989. Trees of Nigeria. A revised version of Nigerian trees (1960, 1964) by Keay, R.W.J., Onochie, C.F.A. & Stanfield, D.P. Clarendon Press, Oxford, United Kingdom. 476 pp.

• Keay, R.W.J., Hoyle, A.C. & Duvigneaud, P., 1958. Caesalpiniaceae. In: Keay, R.W.J. (Editor). Flora of West Tropical Africa. Volume 1, part 2. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 439–484.

Other references

• Adekunle, A.A., 2000. Antifungal property of the crude extracts of Brachystegia eurycoma and Richardia brasiliensis. Nigerian Journal of Natural Products and Medicine 4: 70–72.

• Ajayi, I.A., Oderinde, R.A., Kajogbola, D.O. & Uponi, J.I., 2006. Oil content and fatty acid composition of some underutilized legumes from Nigeria. Food Chemistry 99(1): 115–120.

• CIRAD Forestry Department, 2008. Naga. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/ naga.pdf. November 2011.

• Femi-Ola, T.O. & Odukoya, E.M., 2008. Studies on the effects of Brachystegia eurycoma (Harms) on termites and fungi. Journal of Pure and Applied Microbiology 2(1): 125–130.

• Ikegwu, O.J., Okechukwu, P.E. & Ekumankana, E.O., 2010. Physico-chemical and pasting characteristics of flour and starch from ‘achi’ Brachystegia eurycoma seed. Journal of Food Technology 8(2): 58–66.

• Ikegwu, O.J., Oledinma, N.U., Nwobasi, V.N. & Alaka, I.C., 2009. Effect of processing time and some additives on the apparent viscosity of ‘achi’ Brachystegia eurycoma flour. Journal of Food Technology 7(2): 34–37.

• Ikojo, H.A., Olajide, O. & Uwadinma, I.J., 2005. Effects of soil media and watering regimes on the growth of Brachystegia eurycoma (Harms) seedlings. Journal of Sustainable Agriculture and the Environment 7(1): 93–98.

• Ndukwu, M.C., 2009. Determination of selected physical properties of Brachystegia eurycoma seeds. Research in Agricultural Engineering 55(4): 165–169.

• Okwu, G.I., Achar, P.N. & Sharma, S.K., 2010. Quantification of aflatoxin B1 in ready-to-use food thickeners in South-east geo-political zone in Nigeria. African Journal of Microbiology Research 4(16): 1788–1793.

• Olubunmi, O. & Oremeyi, J., 2011. Preliminary evaluation of Brachystegia eurycoma seed mucilage as tablet binder. International Journal of Pharmaceutical Research and Innovation 3: 1–6.

Author(s)

• L.P.A. Oyen, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Oyen, L.P.A., 2012. Brachystegia eurycoma Harms. [Internet] Record from PROTA4U. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 23 December 2024.

• See the Prota4U database.