Poga oleosa (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Fruit
Vegetable oil
Dye / tannin
Medicinal
Timber
Forage / feed
Food security
Conservation status

Poga oleosa Pierre

Protologue: Bull. Mens. Soc. Linn. Paris 2: 1254 (1896).

Family: Anisophylleaceae

Vernacular names

African brazil nut, inoi nut (En). Erable d’Afrique (Fr).

Origin and geographic distribution

Poga oleosa occurs in southern Nigeria, Cameroon, Equatorial Guinea and Gabon.

Uses

The wood, known in Cameroon as ‘ovoga’ and in Gabon as ‘afo’, is used for joinery, interior trim, furniture, boxes, crates, veneer, plywood, particle board and fibre board. It is traditionally used for canoes. It is suitable for light construction, vehicle bodies, musical instruments, toys, novelties, vats and turnery.

The sweet fruit pulp is edible. The seeds can be eaten fresh or after roasting. They are often added to sauces. They resemble the brazil nut (Bertholletia excelsa Humb. & Bonpl.) from tropical America in flavour and taste. The seed oil has some resemblance to olive oil and groundnut oil, and is used for cooking. The residual meal remaining after expression of the oil is suitable as feed for cattle. Bark decoctions are taken as emetic, whereas powdered bark is applied to wounds and skin diseases. The stone wall of the fruit is burnt and pulverized, and then applied to soothe toothache. Seed oil is taken as purgative in the treatment of gonorrhoea and as a massage oil. The bark, which is rich in tannin, has been used for dyeing cloth blackish.

Production and international trade

The wood of Poga oleosa has been exported in small amounts from Cameroon and Gabon. In 1961 Cameroon exported 1300 m³ of logs. Gabon exported on average 230 m³ of sawn wood in the period 1959–1964 and Equatorial Guinea 3200 m³/year of logs in the period 1959–1968. The export of logs from Gabon was 100 m³ in 2003, 265 m³ in 2004 and 780 m³ in 2005. In Gabon a ban on commercial exploitation has been introduced in 2009 for a period of 25 years. Seeds are fairly commonly available on local markets in Cameroon and Gabon. They are imported in Equatorial Guinea from Cameroon.

Properties

The heartwood is pinkish white to pinkish brown, becoming greyish upon exposure, and distinctly demarcated from the white to greyish, 2–5 cm wide sapwood. The grain is straight to slightly wavy, texture coarse. Quarter-sawn surfaces show a silver-grain figure. The wood is lustrous.

The wood is lightweight, with a density of 400–500 kg/m³ at 12% moisture content. It air dries and kiln dries fairly rapidly, with some risk of distortion, checking and warping in backsawn boards. However, the drying rates of boards are quite variable. The rates of shrinkage are moderate, from green to oven dry 2.5–3.2% radial and 6.9–9.6% tangential. Once dry, the wood is moderately stable in service.

At 12% moisture content, the modulus of rupture is 78–90 N/mm², modulus of elasticity 6370–7160 N/mm², compression parallel to grain 35–38 N/mm², shear 6–6.5 N/mm², cleavage 7.5–13 N/mm and Chalais-Meudon side hardness 0.9–1.8.

The wood is easy to saw and work with ordinary equipment. Planing is somewhat difficult due to the coarse texture. The use of a filler is needed to obtain a good finish and polish, and also for painting and varnishing. The nailing and screwing characteristics are satisfactory, as well as the gluing properties. The wood peels and slices well, producing good-quality veneer. It is moderately durable, being moderately resistant to fungi, fairly resistant to dry-wood borers and susceptible to termites. The wood is easy to treat with preservatives.

The weight of 100 dry seeds is about 80 g. The seeds contain per 100 g: total mineral matter 3.8 g, protein 19 g, fat 69 g, cellulose 0.6 g and other extractive matters 6.5 g. Hexane extraction of the seeds resulted in an oil which is fluid at ambient temperature and is mainly composed of triglycerides. Methanolic fruit extracts showed anti-inflammatory activity, inhibiting carrageenan-induced paw oedema in rats, and antibacterial activity against Staphylococcus aureus and Bacillus subtilis.

Adulterations and substitutes

The fruit of Poga oleosa strongly resembles that of Panda oleosa Pierre, which is used for similar purposes but differs in the more smooth stone.

Description

Evergreen, medium-sized to large tree up to 40(–45) m tall; bole branchless for up to 20 m, usually straight and cylindrical, up to 100(–150) cm in diameter, often with broad and rounded buttresses; bark surface smooth to rough or irregularly scaly, grey to greyish brown, inner bark granular, pink with whitish bands; crown rounded, with large, ascending branches; twigs glabrous. Leaves alternate, simple; stipules up to 1.5 cm long, early caducous; petiole 1–2 cm long, stout; blade broadly elliptical, 7–15 cm × 5–7 cm, rounded at base and apex, margins entire but slightly inrolled, leathery, glabrous, with glandular dots below, glossy, pinnately veined with numerous lateral veins. Inflorescence a panicle composed of spikes, short-hairy, many-flowered. Flowers usually functionally unisexual, regular, 4-merous, small, whitish, sessile; sepals fused at base, triangular, c. 1.5 mm long; petals free, c. 3 mm long, 5–7-lobed with gland at apex of the slender lobes; stamens 8, free, nearly sessile; ovary inferior, 4-celled, styles 4, short. Fruit a globose to ellipsoid, fleshy drupe 4–7 cm in diameter, greenish with numerous brownish lenticels; stone nearly globose, 3.5–5 cm in diameter, distinctly rippled, very hard, 2–4-seeded. Seeds ovoid, 2–2.5 cm × 1–1.5 cm, brown, oily.

Other botanical information

Poga comprises a single species, and is classified together with Anisophyllea (pantropical), Combretocarpus (tropical Asia) and Polygonanthus (tropical America) in the family Anisophylleaceae. Formerly these genera have been included in Rhizophoraceae.

Anatomy

Wood-anatomical description (IAWA hardwood codes):

• Growth rings: 2: growth ring boundaries indistinct or absent.
• Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; (23: shape of alternate pits polygonal); 25: intervessel pits small (4–7 μm); 26: intervessel pits medium (7–10 μm); 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 43: mean tangential diameter of vessel lumina ≥ 200 μm; 46: ≤ 5 vessels per square millimetre; (58: gums and other deposits in heartwood vessels).
• Tracheids and fibres: 61: fibres with simple to minutely bordered pits; (62: fibres with distinctly bordered pits); 66: non-septate fibres present; (68: fibres very thin-walled); 69: fibres thin- to thick-walled.
• Axial parenchyma: 79: axial parenchyma vasicentric; 80: axial parenchyma aliform; 82: axial parenchyma winged-aliform; 83: axial parenchyma confluent; (92: four (3–4) cells per parenchyma strand); 93: eight (5–8) cells per parenchyma strand; (94: over eight cells per parenchyma strand).
• Rays: 98: larger rays commonly 4- to 10-seriate; 99: larger rays commonly > 10-seriate; 102: ray height > 1 mm; 103: rays of two distinct sizes; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 107: body ray cells procumbent with mostly 2–4 rows of upright and/or square marginal cells; 109: rays with procumbent, square and upright cells mixed throughout the ray; (110: sheath cells present); 114: ≤ 4 rays per mm; 115: 4–12 rays per mm.

(N.P. Mollel, P.E. Gasson & E.A. Wheeler)

Growth and development

In a test in Gabon, 57% of seedlings planted in the open survived after one year and 87% of seedlings planted in the undergrowth of opened-up forest; after 6 years the survival rates were 18% and 76%, and after 11 years 8% and 61%, respectively. The young trees in the opened-up forest reached an average height of 22 m and a mean bole diameter of 24 cm 11 years after planting. Poga oleosa is classified as a shade bearer.

In Cameroon fruits ripen in June–August and January–March. Trees produce fruits about once every two years. The fruit stones are dispersed by elephants which eat the fruits. However, in a test in Cameroon, stones collected from elephant dung as well as fresh stones failed to germinate within the test period of one year. Gorillas also eat the fruits.

Ecology

Poga oleosa is a canopy tree of lowland humid evergreen forest, where it is often found in valleys, also in swamp forest. It may be found in secondary forest associated with okoumé (Aucoumea klaineana Pierre), where it often shows better growth than the latter species. It is sometimes a relic in farmland.

Propagation and planting

The germination of fruit stones is irregular and may take a long period. Wildlings can be used for planting, but they are often rare in the forest.

Management

In general, Poga oleosa is quite uncommon in the forest; only locally it is more common or even abundant. In forests in south-western Cameroon, the average density of Poga oleosa trees with a bole diameter of more than 60 cm is 0.06 per ha, with an average wood volume of 0.62 m³/ha. In Gabon the average wood volume has been recorded as 0.56 m³/ha. The trees are sometimes left standing after forest clearance because they are valued by the local population for their oil-rich seeds.

In Gabon Poga oleosa has been planted in reforestation projects. It was considered promising, but needed to be planted under light to moderate shade conditions.

Diseases and pests

In Gabon longicorn beetles have been recorded as a common pest in standing trees.

Yield

A bole branchless for 18 m and with a diameter of 90 cm may yield 10 m³ of wood. The mean weight of the fruit is 90 g, that of the stone 40 g, and that of the seed 5 g.

Handling after harvest

Logs should be removed rapidly from the logging sites after harvesting because they are moderately susceptible to attacks by fungi and insects.

Genetic resources

Poga oleosa has a restricted area of distribution and is usually not abundant in the forest. It might be easily liable to genetic erosion, although it has been excluded from commercial exploitation in Gabon.

Prospects

Although Poga oleosa is a multipurpose tree which is not only important for its timber, but also for its edible, oil-rich seeds and as medicinal plant, little is known about many aspects, particularly about silviculture, management and propagation. At present, Poga oleosa does not seem to have good prospects for more intensified timber exploitation. However, tests in Gabon showed rapid growth of seedlings planted in the undergrowth of opened-up forest, and this may offer possibilities for enrichment planting in natural forest. The main difficulty is the irregular and slow germination of seeds.

More research is needed on the properties and market opportunities of the seed oil. Some applications in traditional medicine have been confirmed by pharmacological studies, and this may offer possibilities for drug development.

Major references

• Bolza, E. & Keating, W.G., 1972. African timbers: the properties, uses and characteristics of 700 species. Division of Building Research, CSIRO, Melbourne, Australia. 710 pp.

• Burkill, H.M., 1997. The useful plants of West Tropical Africa. 2nd Edition. Volume 4, Families M–R. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 969 pp.

• CIRAD Forestry Department, 2009. Ovoga. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/ovoga.pdf. September 2011.

• CTFT (Centre Technique Forestier Tropical), 1950. Ovoga. Fiche botanique et forestière. Bois et Forêts des Tropiques 14: 145–148.

• Eyog Matig, O., Ndoye, O., Kengue, J. & Awono, A. (Editors), 2006. Les fruitiers forestiers comestibles du Cameroun. IPGRI Regional Office for West and Central Africa, Cotonou, Benin. 204 pp.

• Ogbole, O.O., Ekor, M.N., Oluremi, B.B., Ajaiyeoba, E.O., Gbolade, A.A., Ayoola, M.A. & Adeyemi, A.A., 2007. Anti-inflammatory and antimicrobial activities of Hippocratea indica root bark and Poga oleosa fruits. African Journal of Traditional, Complementary and Alternative Medicines 4(3): 372–376.

• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.

• Vivien, J. & Faure, J.J., 1985. Arbres des forêts denses d’Afrique Centrale. Agence de Coopération Culturelle et Technique, Paris, France. 565 pp.

• Vivien, J. & Faure, J.J., 1996. Fruitiers sauvages d’Afrique: espèces du Cameroun. Ministère Français de la Coopération, Paris, France & CTA, Wageningen, Netherlands. 416 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.

Other references

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• de Saint-Aubin, G., 1963. La forêt du Gabon. Publication No 21 du Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 208 pp.

• Gassita, J.N., Nze Ekekang, L., De Vecchy, H., Louis, A.M., Koudogbo, B. & Ekomié, R. (Editors), 1982. Les plantes médicinales du Gabon. CENAREST, IPHAMETRA, mission ethnobotanique de l’ACCT au Gabon, 10–31 juillet 1982. 26 pp.

• 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.

• Koumba Zaou, P., Mapaga, D., Nze Nguema, S. & Deleporte, P., 1998. Croissance de 13 essences de bois d’œuvre plantées en forêt Gabonaise. Bois et Forêts des Tropiques 256(2): 21–32.

• Louppe, D., Deleporte, P., Vigneron, P. & Béhaghel, I., 1999. Projet OIBT PD 10/95 REV. 2 (F). Evaluation des essences indigènes de bois d’œuvre en vue du développement des plantations forestières au Gabon. Rapport final Assistance technique du CIRAD-Forêt, Libreville – Montpellier. 201 pp.

• Nchanji, A.C. & Plumptre, A.J., 2003. Seed germination and early seedling establishment of some elephant-dispersed species in Banyang-Mbo Wildlife Sanctuary, south-western Cameroon. Journal of Tropical Ecology 19(3): 229–237.

• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.

• Normand, D. & Paquis, J., 1976. Manuel d’identification des bois commerciaux. Tome 2. Afrique guinéo-congolaise. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 335 pp.

• Pambou Tchivounda, H., Koudogbo, B., Pouet, Y. & Casadevall, E., 1992. Composition en acides gras et triglycerides des graines comestibles de cinq arbres de la forêt gabonaise. Revue Française des Corps Gras 39(5): 147–152.

• Sallenave, P., 1955. Propriétés physiques et mécaniques des bois tropicaux de l’Union française. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 129 pp.

• Sallenave, P., 1964. Propriétés physiques et mécaniques des bois tropicaux. Premier supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 79 pp.

• Sunderland, T.C.H. & Obama, C., 1999. A preliminary market survey of the non-wood forest products of Equatorial Guinea. In: Sunderland, T.C.H., Clark, L.E. & Vantomme, P. (Editors). Non-wood forest products of Central Africa: current research issues and prospects for conservation and development. FAO, Rome, Italy. pp. 211–220.

• Tailfer, Y., 1989. La forêt dense d’Afrique centrale. Identification pratique des principaux arbres. Tome 2. CTA, Wageningen, Pays-Bas. pp. 465–1271.

• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.

• Tobe, H. & Raven, P.H., 1988. Floral morphology and evolution in Anisophylleaceae. Botanical Journal of the Linnean Society 98(1): 1–25.

• White, L. & Abernethy, K., 1997. A guide to the vegetation of the Lopé Reserve, Gabon. 2nd edition. Wildlife Conservation Society, New York, United States. 224 pp.

Sources of illustration

• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.

• White, L. & Abernethy, K., 1997. A guide to the vegetation of the Lopé Reserve, Gabon. 2nd edition. Wildlife Conservation Society, New York, United States. 224 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.

Author(s)

• A.T. Tchinda, Institut de Recherches Médicales et d’Etudes des Plantes Médicinales (IMPM), Ministère de la Recherche Scientifique et de l’Innovation, B.P. 6163, Yaoundé, Cameroun

Correct citation of this article

Tchinda, A.T., 2012. Poga oleosa Pierre. In: 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. Accessed 17 December 2024.

• See the Prota4U database.