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Zanthoxylum gilletii (De Wild.) P.G.Waterman

Taxon 24: 363 (1975).
Chromosome number
2n = 64
Fagara macrophylla (Oliv.) Engl. (1896), Fagara tessmannii Engl. (1911), Fagara amaniensis Engl. (1917), Zanthoxylum tessmannii (Engl.) J.F.Ayafor (1984).
Vernacular names
African satinwood, white African mahogany (En). Olon dur, citronnier d’Afrique, faux citronnier (Fr).
Origin and geographic distribution
Zanthoxylum gilletii is widespread, occurring from Guinea and Sierra Leone east to Kenya and south to northern Angola, Zimbabwe and Mozambique. It is fairly commonly planted within its distribution area, often as an individual tree, but sometimes also in pure stands.
The wood, often traded as ‘olonvogo’ or ‘olon’, is used for construction in house building, for flooring, joinery, interior trim, panelling, doors, shipbuilding, vehicle bodies, furniture, cabinet work, mine props, railway sleepers, handles, ladders, sporting goods, agricultural implements, drums, toys, novelties, boxes, crates, turnery, veneer and plywood. The wood is also used as firewood and for charcoal production.
Zanthoxylum gilletii is important in traditional medicine. The bark of stem and roots is commonly used as an analgesic, especially to treat burns, rheumatism, headache, stomach-ache, toothache and pain after childbirth. The bark is also taken against colic and fever and is considered to have aphrodisiac properties. Bark decoctions are taken against urogenital problems including kidney complaints and gonorrhoea, as a vermifuge and as an enema against severe diarrhoea. The bark is applied externally to treat cough, colds, skin complaints and smallpox. It is also used as fish poison and arrow poison. The leaves are used to treat heart complaints and snake bites, whereas a leaf decoction is taken to treat cough, gonorrhoea and schistosomiasis, and a leaf maceration to treat diarrhoea and gastritis. Leaf sap is applied externally against an enlarged spleen.
The stem protuberances are used as plugs and the roots are used as chewing sticks to clean the teeth. Young shoots are added to sauces for flavouring and in Kenya leaves are added to tea for this purpose. Pollen and nectar are collected from the flowers by honey bees. The seeds yield an edible oil. Zanthoxylum gilletii is occasionally planted as an ornamental shade tree.
Production and international trade
The timber of Zanthoxylum gilletii has little importance on the international market and most of the trade is for local use. Trade statistics are not available, but the officially registered timber extraction from Kakamega Forest in Kenya declined from 645 m³/year in the 1930s to less than 100 m³ in 2000.
The heartwood is pale yellow to bright yellow or yellowish brown, darkening upon exposure, and indistinctly demarcated from the narrow sapwood. The grain is interlocked, texture fine to moderately coarse. Quartercut surfaces show a stripe figure and backsawn surfaces occasionally have a fiddleback figure. Freshly cut wood has a sweet scent. The wood has a silky lustre.
The wood is moderately heavy to heavy, with a density of (550–)720–1040 kg/m³ at 12% moisture content. It air dries fairly rapidly with little degrade, although cracks may develop in boards. Boards of 2.5 cm thick can be air dried in 6 weeks, boards of 5 cm thick in 3 months. Kiln drying usually does not cause problems. However, the rates of shrinkage are moderate to high, from green to oven dry 4.3–6.5% radial and 8.7–10.2% tangential.
The wood is strong and hard. At 12% moisture content, the modulus of rupture is (86–)114–266 N/mm², modulus of elasticity 8500–18,400 N/mm², compression parallel to grain (48–)58–104 N/mm², compression perpendicular to grain 7 N/mm², shear 10 N/mm², cleavage 16–25 N/mm, Janka side hardness 3650–7790 N, Janka end hardness 5330–9120 N and Chalais-Meudon side hardness 5.2–13.
The wood usually saws moderately well, but is rather difficult to work. Reduction of cutting angles to 15° gives best results in planing. The wood can be finished to a smooth and lustrous surface, but splitting and a rough finish may occur after machine mortising and boring; good mouldings are possible when sharp cutters are used. The nailing properties are good, but gluing properties are variable. The steam-bending properties are excellent. The wood is only moderately durable and often susceptible to termite, Lyctus and marine borer attacks. The heartwood is moderately resistant to impregnation by preservatives, the sapwood permeable.
The major volatile constituents isolated from the bark are the sesquiterpenes germacrene B, γ-elemene and germacrone. The bark contains isoquinoline alkaloids; the root bark contains larger amounts than the stem bark. The quaternary benzophenanthridine nitidine and the isobutylamide fagaramide are major constituents. The first compound lowered blood pressure in tests with rabbits and showed cytotoxic activity in tumour cell lines, whereas the latter compound and some other isobutylamides showed insecticidal and molluscicidal activities. The acridone alkaloid xanthoxoline isolated from the bark exhibited potent antifeedant activity against larvae of Spodoptera spp. Chelerythrine is another alkaloid isolated from the bark; it showed analgesic effect and antibacterial, antifungal and anthelmintic activities. Skimmianine, a furoquinoline alkaloid also present in the bark, showed sedative, hypothermic and antidiuretic effects in rats and mice. The heartwood contains coumarine derivatives such as 6, 7-dimethoxycoumarine; this compound has anti-inflammatory, analgesic, choleretic, hypotensive and tranquilizing properties. Saponins are present in bark and leaves. Extracts of root bark and stem bark showed considerable antimalarial activity in vitro using multi-drug resistant strains of Plasmodium falciparum. Leaves showed good results in the treatment of sickle-cell anaemia patients, probably due to the presence of p-hydroxybenzoic acid and similar benzoic acid derivatives.
The leaves yield a volatile oil, with an ocimene derivative as major constituent (about 43%) and additionally α-pinene and α-phellandrene.
Deciduous small to fairly large tree up to 35 m tall; bole branchless for up to 15(–25) m, usually straight and cylindrical, up to 90(–150) cm in diameter, with many woody, prickle-bearing protuberances up to 3 cm long but old trees often lacking these, often with indistinct buttresses at base; outer bark grey to greyish brown, smooth to slightly rough, inner bark granular, yellowish brown, often mottled with orange; crown spreading; branches glabrous, armed with conical prickles up to 8 mm long. Leaves alternate, clustered at ends of branches, imparipinnately compound with 13–27(–51) leaflets, up to 120(–150) cm long; stipules absent; rachis glabrous, sometimes with prickles; petiolules up to 1 cm long; leaflets alternate to nearly opposite, elliptical-oblong, (8–)14–30 cm × 3.5–10 cm, cuneate to rounded and asymmetrical at base, shortly acuminate to obtuse at apex, margin entire or sometimes slightly toothed, leathery, glabrous, with many minute glandular dots, pinnately veined with 8–18 pairs of lateral veins. Inflorescence a terminal or axillary pyramidal panicle 20–35 cm long, many-flowered with flowers in clusters. Flowers unisexual, regular, 5-merous, small, nearly sessile; sepals united halfway, ovate to circular, 0.5–1 mm long; petals obovate to fiddle-shaped, 1–2.5 mm long, white, turning brown; male flowers with 5 stamens varying in length, disk dome-shaped and lobed, ovary rudimentary; female flowers with superior, ovoid ovary 1–1.5 mm long, shortly stiped, stamens rudimentary. Fruit a globose follicle 3.5–6 mm in diameter, reddish, glandular pitted, dehiscent, 1(–2)-seeded. Seed globose, 2.5–3.5 mm in diameter, black and shiny. Seedling with epigeal germination; hypocotyl 3–4 cm long; cotyledons oblong, 1–1.5 cm long, leafy; first leaves simple.
Other botanical information
Zanthoxylum is pantropical and comprises about 200 species, with tropical America being richest in species. Mainland Africa harbours about 35 species, whereas about 5 species are endemic to Madagascar.
The wood of Zanthoxylum becquetii (G.C.C.Gilbert) P.G.Waterman (synonym: Fagara becquetii G.C.C.Gilbert) has been used in Rwanda for construction; it is reported as hard and durable. The wood of Zanthoxylum renieri (G.C.C.Gilbert) P.G.Waterman (synonym: Fagara renieri G.C.C.Gilbert), occurring in eastern DR Congo and Rwanda, has been used for making canoes.
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; (24: intervessel pits minute ( 4 μm)); 25: intervessel pits small (4–7 μm); 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); 58: gums and other deposits in heartwood vessels. Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 69: fibres thin- to thick-walled. Axial parenchyma: 79: axial parenchyma vasicentric; 80: axial parenchyma aliform; 81: axial parenchyma lozenge-aliform; (83: axial parenchyma confluent); 92: four (3–4) cells per parenchyma strand; 93: eight (5–8) cells per parenchyma strand. Rays: 97: ray width 1–3 cells; 104: all ray cells procumbent; (106: body ray cells procumbent with one row of upright and/or square marginal cells); 115: 4–12 rays per mm. Secretory elements and cambial variants: 131: intercellular canals of traumatic origin. Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.
(N.P. Mollel, P. Détienne & E.A. Wheeler)
Growth and development
Zanthoxylum gilletii grows fairly rapidly. Seedlings may reach a height of 40–70 cm after the first year, and annual growth rates are 35–50 cm. In Côte d’Ivoire trees with a bole diameter of 50 cm have been found in secondary forest of 40 years old. Trees may start flowering when 10 years old. Flowering is irregular, probably due to variable climatic conditions. Trees flower for about 2 months. Fruits ripen about 3 months after flowering. In Kenya the seeds of most Zanthoxylum gilletii trees ripen in the rainy season, which is advantageous for germination. The seeds are probably mainly dispersed by birds and monkeys. Trees may flower and fruit once a year or once in every two years.
Zanthoxylum gilletii occurs in evergreen rainforest, in East Africa up to 2400 m altitude. The mean annual rainfall in its area of distribution is 1200–2400 mm. Zanthoxylum gilletii usually occurs scattered in the forest. In West and Central Africa it is a pioneer species that is most common in secondary forest. Seedlings can be common in burnt forest. Zanthoxylum gilletii prefers well-drained soils.
Propagation and planting
Seedlings are light-demanding and natural regeneration may be abundant in large gaps in the forest and in regrowth of old farmland. In Liberia seedlings are commonly present in such localities, but reportedly never gregarious. Fruits should be collected from the tree before they open but when already reddish brown. They should be dried in the sun for 1–2 days, and subsequently the seed can be shaken out. The 1000-seed weight is 15–35 g. Germination starts 3 weeks after sowing. Seeds are recalcitrant and the germination rate is often low. Germination rates of 20–50% have been reported, but in western Kenya rates of up to 80% in 75–120 days. The oily and hard seed coat contributes to the often poor germination. Washing seeds thoroughly with a soap solution improves the germination rate and reduces the germination period significantly. In West Africa it has been recorded that germination is rapid and that viability of the seed is short. The seed should be kept in the shade, and can be stored for up to 2 months. To prevent insect attacks, ash should be added. Wildlings are commonly used for planting because of the erratic germination. Seedlings are pricked out into tubes at 5–12 days after germination, or 3–4 seeds are sown directly in tubes. The seedlings should be grown in the shade and slowly hardened. They are ready for transplanting after 5–7 months. The usual spacing is 3.5–5 m × 3.5–5 m, resulting in 400–800 stems/ha.
Zanthoxylum gilletii trees often occur scattered in the forest in low densities; for south-western Cameroon an average exploitable timber volume of less than 0.1 m³/ha has been recorded. Planting should be done at the onset of the rainy season in areas where irrigation is not possible. Planting holes are 30–45 cm in diameter and 45–60 cm deep. In Kenya phosphate fertilizers are applied, and manure is sometimes also applied. At the usual spacing thinning is not needed, but at spacings of less than 3.5 m × 3.5 m first and second thinnings at 8 years and 14 years, respectively, are needed. The tree can be managed by coppicing.
Diseases and pests
Damping-off disease can be a serious problem in the nursery, especially when the soil is poorly drained. Defoliators are common, but usually not problematic. Borers eating the terminal bud resulting in forked stems have been recorded in Guinea. Seeds may be commonly infested with insect larvae.
Logging for timber is usually done during the dry season when the forests where Zanthoxylum gilletii occurs can be entered more easily. Where demand for the bark exists, logs are debarked after harvesting.
Handling after harvest
The wood is susceptible to stain and logs should be removed from the forest immediately after felling or be treated with an anti-stain solution.
Genetic resources
Although Zanthoxylum gilletii is widespread, there is some concern about genetic erosion. Wood loggers target big straight trees and these have become scarce in many regions. In forests in Kenya regeneration is often poor due to grazing and heavy pressure by neighbouring communities.
Zanthoxylum gilletii may have good prospects as a plantation timber tree. However, more research is needed on propagation to overcome the often poor seed germination and to develop proper techniques for vegetative propagation including in-vitro propagation. Suitable methods of management of natural forest where Zanthoxylum gilletii is an important constituent should also be investigated. Abundant natural regeneration has been recorded in logged-over forest, which makes it a suitable candidate for sustainable timber exploitation.
The medicinal properties deserve more attention. Several of the claimed activities in traditional medicine have been confirmed by pharmacological research, and a next step might be the development of safe and standardized plant-based drugs.
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.
• Katende, A.B., Birnie, A. & Tengnäs, B., 1995. Useful trees and shrubs for Uganda: identification, propagation and management for agricultural and pastoral communities. Technical Handbook 10. Regional Soil Conservation Unit, Nairobi, Kenya. 710 pp.
• Kokwaro, J.O., 1982. Rutaceae. In: Polhill, R.M. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. 52 pp.
• Latham, P., 2004. Useful plants of Bas-Congo province, Democratic Republic of the Congo. DFID, London, United Kingdom. 320 pp.
• Maundu, P. & Tengnäs, B. (Editors), 2005. Useful trees and shrubs for Kenya. World Agroforestry Centre - East and Central Africa Regional Programme (ICRAF-ECA), Technical Handbook 35, Nairobi, Kenya. 484 pp.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
• Phongphaew, P., 2003. The commercial woods of Africa. Linden Publishing, Fresno, California, United States. 206 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan, 248 pp.
• World Agroforestry Centre, undated. Agroforestree Database. [Internet] World Agroforestry Centre (ICRAF), Nairobi, Kenya. resources/databases/ agroforestree. Accessed September 2007.
Other references
• Akoègninou, A., van der Burg, W.J. & van der Maesen, L.J.G. (Editors), 2006. Flore analytique du Bénin. Backhuys Publishers, Leiden, Netherlands. 1034 pp.
• Beentje, H.J., 1994. Kenya trees, shrubs and lianas. National Museums of Kenya, Nairobi, Kenya. 722 pp.
• Fouarge, J. & Gérard, G., 1964. Bois du Mayumbe. Institut National pour l’Etude Agronomique du Congo (INEAC), Brussels, Belgium. 579 pp.
• Gilbert, G., 1958. Rutaceae. In: Robyns, W., Staner, P., Demaret, F., Germain, R., Gilbert, G., Hauman, L., Homès, M., Jurion, F., Lebrun, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 7. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 69–108.
• Hawthorne, W.D., 1995. Ecological profiles of Ghanaian forest trees. Tropical Forestry Papers 29. Oxford Forestry Institute, Department of Plant Sciences, University of Oxford, United Kingdom. 345 pp.
• Hawthorne, W. & Jongkind, C., 2006. Woody plants of western African forests: a guide to the forest trees, shrubs and lianes from Senegal to Ghana. Kew Publishing, Royal Botanic Gardens, Kew, United Kingdom. 1023 pp.
• InsideWood, undated. [Internet] Accessed May 2007.
• Kubo, I., Matsumoto, T., Klocke, J.A. & Kamikawa, T., 1984. Molluscicidal and insecticidal activities of isobutylamides isolated from Fagara macrophylla. Experientia 40(4): 340–341.
• Letouzey, R., 1963. Rutacées. Flore du Gabon. Volume 6. Muséum National d’Histoire Naturelle, Paris, France. pp. 3–109.
• Mendonça, F.A., 1963. Rutaceae. In: Exell, A.W., Fernandes, A. & Wild, H. (Editors). Flora Zambesiaca. Volume 2, part 1. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 180–210.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Oguntimein, B., El Alfy, T.S. & Elsohly, M.A., 1985. Volatile oils of Zanthoxylum rigidifolium and Zanthoxylum gilletii. Fitoterapia 56(4): 240–242.
• 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.
• Ruberto, G. & Tringali, C., 1998. Composition of the essential oil from the bark of Fagara macrophylla. Journal of Essential Oil Research 10(4): 443–445.
• Siepel, A., Poorter, L. & Hawthorne, W.D., 2004. Ecological profiles of large timber species. In: Poorter, L., Bongers, F., Kouamé, F.N. & Hawthorne, W.D. (Editors). Biodiversity of West African forests. An ecological atlas of woody plant species. CABI Publishing, CAB International, Wallingford, United Kingdom. pp. 391–445.
• Tringali, C., Spatafora, C., Cali, V. & Simmonds, M.S.J., 2001. Antifeedant constituents from Fagara macrophylla. Fitoterapia 72(5): 538–543.
• Vivien, J. & Faure, J.J., 1985. Arbres des forêts denses d’Afrique Centrale. Agence de Coopération Culturelle et Technique, Paris, France. 565 pp.
• Voorhoeve, A.G., 1979. Liberian high forest trees. A systematic botanical study of the 75 most important or frequent high forest trees, with reference to numerous related species. Agricultural Research Reports 652, 2nd Impression. Centre for Agricultural Publishing and Documentation, 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.
• Zirihi, G.N., Mambu, L., Guédé-Guina, F., Bodo, B. & Grellier, P., 2005. In vitro antiplasmodial activity and cytotoxicity of 33 West African plants used for the treatment of malaria. Journal of Ethnopharmacology 98: 281–285.
Sources of illustration
• Hawthorne, W. & Jongkind, C., 2006. Woody plants of western African forests: a guide to the forest trees, shrubs and lianes from Senegal to Ghana. Kew Publishing, Royal Botanic Gardens, Kew, United Kingdom. 1023 pp.
• Voorhoeve, A.G., 1979. Liberian high forest trees. A systematic botanical study of the 75 most important or frequent high forest trees, with reference to numerous related species. Agricultural Research Reports 652, 2nd Impression. Centre for Agricultural Publishing and Documentation, 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.
M.M. Okeyo
Londiani Regional Research Centre, P.O. Box 382 – 20203, Londiani, Kenya

D. Louppe
CIRAD, Département Environnements et Sociétés, Cirad es-dir, Campus international de Baillarguet, TA C-DIR / B (Bât. C, Bur. 113), 34398 Montpellier Cedex 5, France
A.A. Oteng-Amoako
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
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
J.R. Cobbinah
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
Photo editor
G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Okeyo, M.M., 2008. Zanthoxylum gilletii (De Wild.) P.G.Waterman. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.

Distribution Map wild

1, base of bole; 2, leaf; 3, leaf base; 4, infructescence.
Redrawn and adapted by Achmad Satiri Nurhaman

tree habit

base of bole

bole with prickles



debarked bole


harvesting fruits

fruiting branch




wood in transverse section

wood in tangential section

wood in radial section