Alstonia congensis (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Carbohydrate / starch
Medicinal
Timber
Ornamental

distribution in Africa (wild)

1, part of branch with leaves; 2, inflorescence; 3, flower; 4, fruit; 5, seed Redrawn and adapted by Achmad Satiri Nurhaman

plantation of 15 years in Côte d’Ivoire

habit of young tree

flowering branch

tree with fruiting branches

wood in transverse section

wood in tangential section

wood in radial section

Alstonia congensis Engl.

Protologue: Bot. Jahrb. Syst. 8: 64 (1887).

Family: Apocynaceae

Synonyms

• Alstonia gilletii De Wild. (1907).

Vernacular names

• Alstonia, cheesewood, stool wood, pattern wood (En).
• Emien (Fr).
• Songati (Po).

Origin and geographic distribution

Alstonia congensis occurs from south-western Nigeria to the Central African Republic, eastern and southern DR Congo, and northern Angola.

Uses

The wood is used for light construction, light carpentry, open boats, moulding, furniture, interior joinery, implements, boxes, crates, matches, pencils, sculptures (e.g. masks), and for veneer and plywood (interior). It is locally popular for the production of household implements because of its good working properties and stability.

A bark decoction is used to treat malaria, gonorrhoea, diarrhoea and other intestinal problems, rheumatic pain, and as a galactagogue, and the bark is also applied as an antidote for arrow poison and as an anthelmintic. The latex is used to treat leucorrhoea, ulcers, scabies, yaws and headache. Lightly roasted leaves are smoked in a pipe as a remedy for cough. The tree is occasionally used as an ornamental or shade tree.

Production and international trade

Although Alstonia timber of Asian origin (from different species; mainly from Indonesia and Malaysia) is important on the international timber market, Alstonia timber is only occasionally exported from African countries, and then probably in mixed consignments of lightweight timber. It is mostly used locally.

Properties

In trade the wood of Alstonia congensis is not distinguished from that of Alstonia boonei De Wild.; it has similar properties. The heartwood is creamy white and indistinctly demarcated from the up to 20 cm wide sapwood. The grain is straight, occasionally wavy, texture moderately coarse. Growth rings indistinct or absent.

The wood is lightweight. The density is 340–400 kg/m³ at 12% moisture content. The shrinkage rates are moderately low, from green to oven dry 3.2–4.0% radial and 5.1–5.5% tangential. The wood dries rapidly, with slight risk of distortion and checking. Once dry, it is stable.

At 12% moisture content, the modulus of rupture is 48–70 N/mm², modulus of elasticity 5800–8800 N/mm², compression parallel to grain 23–36 N/mm², shear 1–2 N/mm², cleavage 7–16 N/mm and Janka side hardness 1825 N.

The wood is easy to saw, although the presence of latex may cause clogging of sawblades. The peeling characteristics are good. Nailing and screwing usually do not cause problems, and gluing, painting and varnishing give good results. The surfaces produced are generally smooth if sharp cutting edges are used. The steam-bending properties are poor.

The wood is not durable. It is easily attacked by fungi and very prone to blue stain. It is susceptible to dry-wood borers, powder-post beetles and termites. Consequently, it is only suited for indoor use and cannot be used in contact with the ground. However, it is easy to treat with preservatives, absorbing over 480 kg/m³ using open tank or pressure systems.

A methanolic leaf extract showed some antimalarial activity in tests on Plasmodium berghei in mice; it suppressed early infection, but showed no effect when the infection was already established. The bark and leaves showed cardio-activity in animal tests. Several alkaloids have been isolated from the bark and leaves. One of these is the indole alkaloid echitamine, which showed several pharmacological activities (e.g. hypotensive activity and relaxing activity of smooth muscles) in animal test models. However, this compound showed only very limited antiplasmodial effect.

Adulterations and substitutes

The wood of the closely related Alstonia boonei is used indiscriminately from that of Alstonia congensis.

Description

• Small to medium-sized tree up to 15(–25) m tall, with latex; bole up to 30(–100) cm in diameter, fluted at the base or with steep buttresses; bark smooth or rough, usually with large lenticels, greyish or pale brown, inner bark creamy or pale yellow, with copious latex; crown layered.
• Leaves in whorls of 4–6(–8), simple and entire; stipules absent; petiole up to 0.5 (–1) cm long, flattened and grooved above, with narrowly triangular colleters at base; blade obovate to spatulate, 8–26 cm × 3.5–11.5 cm, cuneate at base, rounded to shortly acuminate at apex, occasionally retuse, leathery, glabrous, many-veined with lateral veins joining near the margin. Inflorescence a terminal, compound, umbel-like cyme up to 25 cm long; peduncle 3.5–12 cm long, stout; bracts up to 2 mm long.
• Flowers bisexual, regular, 5-merous, fragrant; pedicel ( 2–)3–5(–9) mm long; sepals up to 3 mm long, fused at base, glabrous but slightly pubescent at margins; corolla cream-coloured, pale yellow or pale pink, pubescent, with tube 4–7.5 mm long, widening near the end, lobes obliquely obovate, 4–10 mm long; stamens inserted in upper part of corolla tube, filaments c. 0.5 mm long, anthers up to 1.5 mm long; ovary superior, ovoid, glabrous or occasionally slightly pubescent, 2-celled, style 1–3.5 mm long, ending in a pistil head composed of a basal ring, a cylindrical central part and an elongate cleft stigmoid apical part.
• Fruit composed of 2 linear follicles 20–45 cm long and 2–4 mm in diameter, glabrous, many-seeded.
• Seeds oblong, flattened, 6–9 mm × 2–2.5 mm, brown, with long hairs up to 2 cm long on the ends.

Other botanical information

Alstonia comprises about 40 species and has a pantropical distribution. Only two species are indigenous in Africa, both belonging to section Alstonia. Alstonia boonei differs from Alstonia congensis in its stalked leaves, pubescent sepals and pubescent follicles, and also in surface sculpturing of the lower leaf epidermis (stomata exposed in Alstonia congensis, concealed below wax chains in Alstonia boonei). In much of the older literature concerning West Africa, the name Alstonia congensis has been erroneously used for Alstonia boonei.

Anatomy

Wood-anatomical description (IAWA hardwood codes):

• Growth rings: (1: growth ring boundaries distinct); (2: growth ring boundaries indistinct or absent).
• Vessels: 5: wood diffuse-porous; (10: vessels in radial multiples of 4 or more common); 13: simple perforation plates; 22: intervessel pits alternate; (23: shape of alternate pits polygonal); (24: intervessel pits minute (≤ 4 μm)); 25: intervessel pits small (4–7 μm); 29: vestured pits; 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 42: mean tangential diameter of vessel lumina 100–200 μm; (43: mean tangential diameter of vessel lumina ≥ 200 μm); 46: ≤ 5 vessels per square millimetre; (47: 5–20 vessels per square millimetre).
• 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.
• Axial parenchyma: 78: axial parenchyma scanty paratracheal; 86: axial parenchyma in narrow bands or lines up to three cells wide; (87: axial parenchyma reticulate); (92: four (3–4) cells per parenchyma strand); 93: eight (5–8) cells per parenchyma strand; (94: over eight cells per parenchyma strand).
• Rays: 97: ray width 1–3 cells; 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; 115: 4–12 rays per mm.
• Secretory elements and cambial variants: 132: laticifers or tanniferous tubes.
• Mineral inclusions: (136: prismatic crystals present); (137: prismatic crystals in upright and/or square ray cells); (141: prismatic crystals in non-chambered axial parenchyma cells); (154: more than one crystal of about the same size per cell or chamber).

(E. Ebanyenle, A.A. Oteng-Amoako & P. Baas)

Growth and development

The seeds are dispersed by wind.

Ecology

Alstonia congensis usually occurs in swampy localities (e.g. Raphia swamps) up to 500 m altitude, but it is sometimes also found on drier, rocky soils. In Equatorial Guinea it is most common in a zone near the coast, with on average almost 2 trees over 30 cm in bole diameter per ha.

Propagation and planting

Propagation of Alstonia congensis by stem cuttings using growth regulators was successful (up to 63% rooting) in Nigeria.

Handling after harvest

The logs float easily in water, and can be transported by rivers. They are very susceptible to insect and fungal attack and should be dried quickly or treated with preservatives after felling. They are not well suited for rotary peeling because they are often deeply fluted.

Genetic resources

Alstonia congensis is considered locally endangered, e.g. in Nigeria, where the bark is commonly collected for medicinal purposes.

Prospects

Export prospects are poor for Alstonia congensis because of the poor durability and limited uses of the wood and the usually small size of the tree. It may be useful as an auxiliary plant in agriculture because it is easy to propagate, grows moderately fast and develops a taproot, which does not interfere with the superficial root system of crops.

The effectiveness of Alstonia congensis and other Alstonia species in the treatment of malaria is controversial, and more research is still needed to confirm the claimed medicinal activities.

Major references

• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 960 pp.

• Chudnoff, M., 1980. Tropical timbers of the world. USDA Forest Service, Agricultural Handbook No 607, Washington D.C., United States. 826 pp.

• CIRAD Forestry Department, 2003. Emien. [Internet] Tropix 5.0. http://tropix.cirad.fr/ afr/emien.pdf. December 2004.

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

• Sidiyasa, K., 1998. Taxonomy, phylogeny, and wood anatomy of Alstonia (Apocynaceae). Blumea Supplement 11. Rijksherbarium / Hortus Botanicus, Leiden University, Leiden, Netherlands. 230 pp.

• World Agroforestry Centre, undated. Agroforestree Database. [Internet] World Agroforestry Centre (ICRAF), Nairobi, Kenya. http://www.worldagroforestry.org/Sites/TreeDBS/aft.asp. January 2005.

Other references

• Awe, S.O. & Poeke, O.O., 1990. Effect of Alstonia congensis on Plasmodium berghei berghei in mice. Fitoterapia 61(3): 225–229.

• de Jong, B.H.J., 1979. A revision of the African species of Alstonia R.Br. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 79–13. Wageningen, Netherlands. 16 pp.

• InsideWood, undated. [Internet] http://insidewood.lib.ncsu.edu/search/. May 2007.

• Jayeola, A.A., 1998. Surface sculpturing of Alstonia boonei De Wild. and A. congensis Engl. (Apocynaceae) and its importance on their taxonomy. Feddes Repertorium 109(5–6): 429–433.

• Ilesanmi, O.R., Aladesanmi, A.J. & Adeoye, A.O., 1988. Pharmacological investigation on the cardiac activity of some Nigerian medicinal plants. Fitoterapia 59(5): 371–376.

• Pauwels, L., 1993. Nzayilu N’ti: guide des arbres et arbustes de la région de Kinshasa Brazzaville. Scripta Botanica Belgica. Volume 4. Jardin botanique national de Belgique, Meise, Belgium. 495 pp.

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

• Rudjiman, Gintings, N., Martawijaya, A. & Ilic, J., 1993. Alstonia R.Br. In: Soerianegara, I. & Lemmens, R.H.M.J. (Editors). Plant Resources of South-East Asia No 5(1). Timber trees: Major commercial timbers. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 82–90.

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

• Teo, S.P., 2001. Alstonia R.Br. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 61–68.

Sources of illustration

• de Jong, B.H.J., 1979. A revision of the African species of Alstonia R.Br. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 79–13. Wageningen, Netherlands. 16 pp.

Author(s)

• R.H.M.J. Lemmens

PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Lemmens, R.H.M.J., 2005. Alstonia congensis Engl. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 6 March 2025.

• See the Prota4U database.