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Pentaclethra macrophylla Benth.

Journ. Bot. (Hook.) 4(30): 330 (1842).
Mimosaceae (Leguminosae - Mimosoideae)
Chromosome number
n = 7, 2n = 26
Vernacular names
African oil bean, Atta bean, Owala oil tree, Congo acacia, nganzi (En). Owala, mubala, arbre à semelles, acacia du Congo (Fr). Sucupira, marroné (Po).
Origin and geographic distribution
Pentaclethra macrophylla occurs in the forest zone of West and Central Africa, from Senegal to south-eastern Sudan and to Angola and on the islands of São Tomé et Príncipe.
Pentaclethra macrophylla is planted or retained along the edges of home gardens and farms mainly for its seed from which an edible oil can be extracted. Throughout the forest zone of West Africa the seeds are eaten boiled or roasted. They are also fermented to yield a snack or condiment with a meaty taste, very popular in south-western Nigeria where it is called ‘ugba’. The empty dry pods are used as fuel for cooking. Farmers protect this species on farms because its open crown does not severely affect crop growth and because some trees are leafless during the growing season. The leaves also contribute to soil fertility. Pentaclethra macrophylla wood, called ‘mubala’ or ‘ovala’, is suitable as fuel wood and for charcoal making. As few trees develop a straight trunk of harvestable size, timber of larger sizes is only occasionally available. The wood is hard and difficult to work, but suitable for poles, railway sleepers and general carpentry. Traditionally, pestles and mortars have been made from it. Ash from wood or pods is used as a mordant in the dyeing industry. In DR Congo the edible caterpillars of the giant silkworm moths Nudaurelia oyemensis (called ‘minsangula’) and Imbrasia obscura (called ‘minsendi’) feed on the leaves. Bees forage the flowers for honey. Pentaclethra macrophylla is used in Africa in traditional human and veterinary medicine. The ripe fruits are applied externally to heal wounds. Extracts of the leaf, stembark, seed and fruit pulp have anti-inflammatory and anthelmintic activity, and are used to treat gonorrhoea and convulsions, and also used as analgesic. The root bark is used as a laxative, as an enema against dysentery and as a liniment against itch. In Cameroon an infusion of the bark is used as an abortifacient. Pentaclethra macrophylla is occasionally planted along roads. It plays a role in various traditional ceremonies.
Production and international trade
Most production is for home or local consumption and no information on production and trade of oil, ‘ugba’ or timber is available.
Unfermented seed contains per 100 g: water 3–10 g, energy 2330–2540 kJ (557–607 kcal), protein 17–22 g, fat 35–52 g, carbohydrate 12–43 g, crude fibre 2.5 g. The fatty acid composition of the oil is: palmitic acid 3–4%, stearic acid 0–2%, arachidic acid 4%, behenic acid 5–6%, lignoceric acid 11–12%, oleic acid 19–29%, linoleic acid 42–54%, linolenic acid 0–3%; in addition 2 unusual long-chain fatty acids are present: hexacosanoic acid 5% and octacosanoic acid 1%. The seed contains the growth-retardant alkaloid paucine (caffeoyl-putrescine). When the seed is fermented to ‘ugba’ it is detoxified. The fermentation causes a marked reduction in protein content, and a slight increase in carbohydrate, oil and ash contents.
The heartwood is reddish brown and not always distinctly demarcated from the whitish or grey sapwood. The grain is interlocked and texture coarse. At 12% moisture content the density is 910 kg/m3. The rates of shrinkage are high, 11–16.5% volumetric. Logs should be quarter sawn before drying. At 12% moisture content, the modulus of rupture is 130–226 N/mm2, modulus of elasticity 16,000–21,150 N/mm2, compression parallel to grain 75.2–83.6 N/mm2, Janka side hardness 11,020 N, Chalais-Meudon side hardness 8.5–14.1. The wood is hard and strong, but difficult to work. It is susceptible to marine borers and occasionally attacked by termites. The silica content is less than 2%.
Medium-sized to fairly large tree up to 35 m tall; bole up to 100 cm in diameter, often crooked and low branching, with irregular, thick buttresses up to 3 m high, or without buttresses; outer bark greyish to reddish brown, thin, flaking irregularly, inner bark fibrous, yellow to orange; twigs brown stellate-hairy. Leaves alternate, bipinnately compound, 20–45 cm long; stipules needle-shaped, 3–5 mm long, caducous, with basal gland; petiole 3–6(–8) cm long, swollen and jointed at base, channeled; pinnae opposite, in 9–13 pairs, (8–)10–14 cm long, at base markedly jointed, with (6–)8–14(–20) pairs of leaflets; leaflets opposite, sessile, obliquely oblong to elliptical, 12–25 mm × 5–10 mm, apex rounded, glabrous except for scattered hairs on margins and midrib below. Inflorescence a terminal or axillary panicle up to 30 cm long, consisting of spikes, many-flowered, densely covered with brownish stellate hairs. Flowers bisexual, regular, 5-merous, small, fragrant, sessile; calyx campanulate, with broadly elliptical lobes, c. 0.5 mm long; petals oblong-lanceolate, c. 3 mm long, basally swollen and fused for c. 1 mm, yellow; stamens 5, c. 5 mm long, yellow, anthers with large gland between the thecae, staminodes 10–15, filiform; ovary superior, sessile, 1-celled, glabrous at first, upper part hairy, style extending during flowering, stigma indistinct. Fruit an obliquely linear-oblong pod up to 50 cm × 10 cm × 2 cm, woody, dark brown, tapering to the base, apex rounded, sides longitudinally ribbed, long-persistent and opening explosively on the tree and then recurving strongly, 5– 8-seeded. Seeds elliptical in outline, flattened, 3.5–7 cm × 2.5–3.5 cm × c. 1 cm, smooth, purplish brown. Seedling with hypogeal germination; cotyledons remaining in the testa; hypocotyl not developing, epicotyl 8–10 cm long, with several scales; leaves alternate, first leaf bipinnate.
Other botanical information
Pentaclethra comprises 3 species, 2 in Africa and 1 in South America. The other African species, Pentaclethra eetveldeana De Wild. & T.Durand, can be distinguished by its smaller leaflets and simple hairs. The American Pentaclethra macroloba (Willd.) O.Kuntze yields timber traded as ‘gavilán’ and is an important medicinal plant.
Growth and development
The bole is often gnarled and twisted and forked at a low level and the base is often damaged by elephants, but trees with a longer straight trunk are occasionally found. Watershoots around the base are common and the tree coppices well. The crown has been described as heavily branched and dense, but also as open and allowing crops to grow well below the tree. Some specimens are leafless during the rainy season, though the species is mostly evergreen. Pentaclethra macrophylla nodulates and fixes atmospheric nitrogen. The main flowering season in West Africa is March–April, with smaller flushes in June and November; in Liberia trees flower in February–April and fruit in September–December. The flowers are strongly fragrant, very rich in nectar and much visited by honeybees.
Pentaclethra macrophylla is common in primary forest and secondary forest and coastal savanna, often in the vicinity of creeks and rivers. It is most common at altitudes up to 500 m, although growth can be good at higher elevations where rainfall is adequate and temperatures are never cooler than 18°C. It requires a mean annual rainfall of (1000–) 1500–2000(–2700) mm and a mean annual temperature of about 25°C. It prefers medium loamy, well-drained soil. The natural distribution suggests that it is adapted to relatively acid soils. It tolerates waterlogging.
Propagation and planting
The seed is recalcitrant and should be planted immediately. Storage at 15°C can extend longevity to about 3 months. There are 50–80 seeds per kg. Mechanical scarification and soaking in water for 24 hours enhances germination. Pentaclethra macrophylla can also be propagated by cuttings, air-layering or budding. Only juvenile stem cuttings will root and are best treated with a growth hormone. Cuttings may produce seed after 4 years, budded trees after 3 years. Although direct sowing is common, better planting material is obtained from seedlings produced in nurseries and hardened off before planting.
Trees of Pentaclethra macrophylla are commonly protected and often tended in farm land, e.g. in DR Congo where it is grown on farms and on abandoned farm land to improve bush fallow. An area around the stem may be clean-weeded to facilitate collection of the seeds.
Diseases and pests
No serious diseases or pests of Pentaclethra macrophylla are known, but many insect species and pathogens attack the pods and seeds. The major insect pests are Cossus cadambae, Sitophilus spp., Spodoptera exempta and several giant silkworms. Some of the insect pests skeletonize the green pods, some bore into the pods and seeds; others lacerate the pods, causing lesions that allow fungal and bacterial pathogens to invade the seeds.
Fruits are available at most periods of the year because the large woody pods are persistent. Harvesting pods is an arduous and dangerous task and collectors may charge as much as half of the yield as their fee.
Handling after harvest
The seeds of Pentaclethra macrophylla are roasted or boiled, or fermented to produce ‘ugba’. The seeds are boiled for 3–12 hours; then the seedcoat is removed. When the cotyledons are cooled to room temperature they are sliced into small pieces of 4–5 cm × 1–2 mm and washed with water. The slices are boiled for 1–2 hours, cooled and soaked in water for 10 hours. Then the slices are drained in a basket lined with banana leaves. The drained slices are wrapped in blanched leaves of banana or Mallotus oppositifolius (Geiseler) Müll.Arg. and incubated at ambient temperature for 4–6 days when prepared for use as a snack or sidedish, or for 7–10 days when prepared as a condiment for soups. The fermentation is proteolytic and proceeds under alkaline conditions. It is caused mainly by Bacillus subtilis, but other Bacillus spp. are also involved, while other bacteria may be present as contaminants.
Genetic resources
Although not immediately endangered by genetic erosion, numbers of Pentaclethra macrophylla have declined strongly in some areas. In Nigeria stands are now largely confined to the south-eastern region and even there regeneration rates seem inadequate. No collections of genetic resources exist. However, the National Centre for Genetic Resources and Biotechnology and the Forestry Research Institute of Nigeria have initiated the study, collection and conservation of edible plant resources, including Pentaclethra macrophylla.
The domestication of Pentaclethra macrophylla as a tree crop in agroforestry has been recommended. Selection of trees with non-shattering pods or with pods that shatter simultaneously and the development of pruning methods that make harvesting easier are desirable.
Major references
• Akindahunsi, A.A., 2004. Physicochemical studies on African oil bean (Pentaclethra macrophylla Benth.) seed. Journal of Food, Agriculture and Environment 2: 14–17.
• Aubréville, A., 1959. La flore forestière de la Côte d’Ivoire. Deuxième édition révisée. Tome premier. Publication No 15. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 369 pp.
• Banks, C.H. & Schoeman, J.P., 1963. Railway sleeper and crossing timbers. Bulletin 41. The Government Printer, Pretoria, South Africa. 54 pp.
• Isu, N.R. & Ofuya, C.O., 2000. Improvement of the traditional processing and fermentation of African oil bean (Pentaclethra macrophylla Bentham) into a food snack - ‘ugba’. International Journal of Food Microbiology 59: 235–239.
• Jones, A.C., Robinson, J.M. & Southwell, K.H., 1987. Investigation into Pentaclethra macrophylla seed oil: identification of hexacosanoic (C26:0) and octacosanoic (C28:0) fatty acids. Journal of the Science of Food and Agriculture 40(2): 189–194.
• Keay, R.W.J., 1989. Trees of Nigeria. A revised version of Nigerian trees (1960, 1964) by R.W.J. Keay, C.F.A. Onochie and D.P. Stanfield. Clarendon Press, Oxford, United Kingdom. 476 pp.
• Ladipo, D.O. & Boland, D.J., 1995. Pentaclethra macrophylla: a multipurpose tree from Africa with potential for agroforestry in the tropics. NFT Highlights, NFTA 95–05, September 1995. Winrock International, Morrilton AR, United States. 4 pp.
• Latham, P., 2004. Useful plants of Bas-Congo province, Democratic Republic of the Congo. DFID, London, United Kingdom. 320 pp.
• Oboh, G. & Ekperigin, M.M., 2004. Nutritional evaluation of some Nigerian wild seeds. Nahrung/Food 48(2): 85–87.
• Voorhoeve, A.G., 1965. Liberian high forest trees. A systematic botanical study of the 75 most important or frequent high forest trees, with reference to numerous related species. Pudoc, Wageningen, Netherlands. 416 pp.
Other references
• Afkah, P.A., Aguwa, C.N. & Agu, R.U., 1999. Studies on the antidiarrhoeal properties of Pentaclethra macrophylla leaf extracts. Phytotherapy Research 13(4): 292–295.
• Akubor, P.I. & Chukwu, J.K., 1999. Proximate composition and selected functional properties of fermented and unfermented African oil bean (Pentaclethra macrophylla) seed flour. Plant Foods for Human Nutrition 54: 227–238.
• Emebiri, L.C. & Anyim, C., 1997. Intraspecific variation in morphological traits of the oil bean tree, Pentaclethra macrophylla. [Internet] Plant Genetic Resources Newsletter 112. publications/pgrnewsletter/nl112.htm. Accessed January 2006.
• Emebiri, L.C., Nwufo, M.I. & Obiefuna, J.C., 1995. Pentaclethra macrophylla: population characteristics, distribution and conservation status in Nigeria. International Tree Crops Journal 8: 69–82.
• Enujiugha, V.N., 2003. Nutrient changes during the fermentation of African oil bean (Pentaclethra macrophylla Benth.) seeds. Pakistan Journal of Nutrition 2(5): 320–323.
• Enujiugha, V.N. & Akanbi, C.T., 2005. Compositional changes in African oil bean (Pentaclethra macrophylla Benth.) seeds during thermal processing. Pakistan Journal of Nutrition 4(1): 27–31.
• Folefoc, G.N., Bisseck, J.P., Fomum, Z.T. & Bodo, B., 2005. Constituents from the roots of Pentaclethra macrophylla. Biochemical Systematics and Ecology 33: 1280–1282.
• Hilditch, T.P., Meara, M.L. & Patel, C.B., 1951. The component acids and glycerides of Pentaclethra (Leguminosae) and Lophira (Ochnaceae) seed fats. Journal of the Science of Food and Agriculture 2(3): 142–148.
• Isu, N.R. & Njoku, H.O., 1997. An evaluation of the microflora associated with fermented African oil bean (Pentaclethra macrophylla Bentham) seeds during ugba production. Plant Foods for Human Nutrition 51: 145–157.
• Ladipo, D.O., Kang, B.T. & Swift, M.J., 1993. Nodulation in Pentaclethra macrophylla Benth.; a multipurpose tree with potential for agroforestry in the humid lowlands of West Africa. Nitrogen Fixing Tree Research Reports 11: 104–115.
• Okwulehie, I.C., 2004. Insect pests and mycoflora of oilbean (Pentaclethra macrophylla Benth.) pods and seeds in southeastern parts of Nigeria. Fruits 59: 25–30.
• Okafor, J.C., 1991. Improving edible species of forest products. [Internet] Unasylva 49(165). documents/show_cdr.asp?url_file=/docrep/u2440e/ u2440e00.htm. Accessed January 2005.
• Okwulehie, I.C., 2004. Insect pests and mycoflora of oilbean (Pentaclethra macrophylla Benth.) pods and seeds in southeastern parts of Nigeria. Fruits 59: 25–30.
• Onyeike, E.N. & Acheru, G.N., 2002. Chemical composition of selected Nigerian oil seeds and physicochemical properties of the oil extracts. Food Chemistry 77: 431–437.
• Oxford Forestry Institute, 1997–2004. Prospect: the wood database. Oxford Forestry Institute, Department of Plant Services, University of Oxford, Oxford, United Kingdom.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan, 248 pp.
• Udosen, E.O. & Ifon, E.T., 1990. Fatty acid and amino acid composition of African oil beans (Pentaclethra macrophylla). Food Chemistry 36: 155–160.
Sources of illustration
• Villiers, J.-F., 1989. Leguminosae - Mimosoideae. Flore du Gabon. Volume 31. Muséum National d’Histoire Naturelle, Paris, France. 185 pp.
• Wilks, C. & Issembé, Y., 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata, Guinée Equatoriale. 546 pp.
G. Oboh
Biochemistry Department, Federal University of Technology, P.M.B. 704, Akure, Ondo State, Nigeria

H.A.M. van der Vossen
Steenuil 18, 1606 CA Venhuizen, Netherlands
G.S. Mkamilo
Naliendele Agricultural Research Institute, P.O. Box 509, Mtwara, Tanzania
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Photo editor
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Oboh, G., 2007. Pentaclethra macrophylla Benth. In: van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA 14: Vegetable oils/Oléagineux. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map wild

1, base of bole; 2, leaf; 3, inflorescence; 4, fruit; 5, seed.
Redrawn and adapted by Achmad Satiri Nurhaman

fruit and inflorescence

open fruit with seeds

young tree