Prota 7(2): Timbers/Bois d’œuvre 2
Engl., Monogr. afrik. Pflanzen-Fam. 4: 13, t. 4 (1900).
Terminalia aemula Diels (1907).
River terminalia, river cluster-leaf (En). Mbombaro, mkulungo, mpululu, mwangati (Sw).
Origin and geographic distribution
Terminalia sambesiaca occurs from south-eastern Kenya south to Zambia, northern Zimbabwe and Mozambique.
The wood is used for building poles, ship masts, stools, mortars, tool handles and beehives. It is suitable for construction, flooring, joinery, interior trim, bridge decking, ship building, furniture, cabinet work, sporting goods, toys, novelties, railway sleepers, mine props, veneer and plywood. It is also used as firewood and for charcoal production.
In traditional medicine the leaves are used to treat stomach-ache and infertility in women, whereas bark and leaf decoctions are applied to treat fever, colds, cancer, stomach ulcers and appendicitis. Powdered root bark is mixed with porridge and eaten to treat bloody diarrhoea.
The heartwood is yellow with brownish stripes on quarter-sawn surfaces, darkening rapidly to yellowish brown or greenish brown, and distinctly demarcated from the cream-coloured, up to 6 cm wide sapwood. The grain is interlocked, texture fine and even.
The wood is moderately heavy, with a density of 750–820 kg/m³ at 12% moisture content. It air dries fairly rapidly, with little degrade. The rates of shrinkage are moderate, from green to 12% moisture content 2.2% radial and 3.7% tangential. Boards of 2.5 cm thick air dry in 6 weeks, and 5 cm thick boards in 3 months. Surface checking and some distortion may occur, especially in kiln drying. Once dry, the wood is moderately stable in service. At 12% moisture content, the modulus of rupture is 93 N/mm², modulus of elasticity 12,740 N/mm², compression parallel to grain 60 N/mm², shear 15 N/mm² and Janka side hardness 6360 N.
The wood is moderately difficult to saw and work with hand and machine tools. It often finishes well, but the use of a filler has been recommended to produce good surfaces. The wood holds nails well, but pre-boring is recommended. The heartwood is moderately durable, being susceptible to termite attack; the sapwood is susceptible to Lyctus attack. The heartwood is resistant to impregnation with preservatives, but the sapwood is permeable.
Methanol extracts of the roots showed marked antibacterial activity against Enterobacter aerogenes, Micrococcus luteus, Pseudomonas aeruginosa, Sarcina sp., Salmonella typhi, Shigella boydii, Staphylococcus aureus and Staphylococcus epidermidis, as well as distinct antifungal activity against Candida albicans, Candida glabrata and Cryptococcus neoformans. Bark extracts also showed antibacterial activity and leaf extracts antifungal properties against Candida albicans and Cryptococcus neoformans. Antifungal activity was found especially in polar fractions of the extract and might be due to the presence of tannins. Root extracts showed strong cytotoxic effects against several human cancer cell lines, e.g. against HeLa cervical cancer cells, T24 bladder cancer cells and BBCE endothelial cells.
Small to fairly large tree up to 40 m tall; bole branchless for up to 18 m, straight or crooked, up to 90 cm in diameter, often slightly buttressed, old trees often with bottle-shaped buttresses up to 4 m high; bark surface greyish to dark brown or nearly black, smooth to slightly grooved, inner bark yellowish with brown streaks; crown layered, with horizontal branches; branchlets with fibrous bark, hairy when young. Leaves arranged spirally, clustered near ends of branchlets, simple and usually entire; stipules absent; petiole up to 4 cm long, hairy; blade elliptical to elliptical-obovate, 7–18 cm × 3–13 cm, cuneate to rounded at base, acuminate at apex, papery, hairy especially on the veins below, pinnately veined with 8–11 pairs of lateral veins. Inflorescence an axillary spike 6–15 cm long, short-hairy; peduncle up to 6 cm long. Flowers bisexual or male, regular, 4–5-merous, whitish sometimes pinkish tinged; receptacle spindle-shaped, c. 3 mm long, hairy; sepals triangular, c. 1.5 mm long; petals absent; stamens usually 10, free, c. 5 mm long; disk annular, hairy; ovary inferior, 1-celled, style 3–5 mm long. Fruit a winged nut, elliptical in outline, 5–7(–9) cm × 2–3(–4.5) cm including the wing, stipe up to 1.5 cm long, reddish brown, finely hairy, indehiscent, 1-seeded.
Terminalia is a pantropical genus of about 200 species. In tropical mainland Africa about 30 species occur naturally, in Madagascar about 35. Terminalia sambesiaca has been confused with Terminalia kilimandscharica Engl., which differs in being a small tree and usually having smaller, less distinctly acuminate and more permanently hairy leaves.
It has been recorded that Terminalia sambesiaca grows rapidly. Annual elongation of the bole results in a layered crown. Flowering usually occurs in December–January. The flowers have a strong and unpleasant smell, and are probably pollinated by flies. Fruits ripen 2–4 months after flowering.
Terminalia sambesiaca occurs in rainforest, dry evergreen forest and riverine forest, less often in savanna woodland and on rocky hills, from sea-level up to 850 m altitude.
Genetic resources and breeding
Although Terminalia sambesiaca is fairly widespread, it is in most regions rather uncommon and larger specimens occur mainly in lowland evergreen forest and riverine forest.
Although Terminalia sambesiaca has been reported to be an excellent timber tree, very little is known about its growth rates, propagation and possibilities for establishing plantations. The strong antifungal activity of the root against Cryptococcus neoformans makes Terminalia sambesiaca a valuable medicinal plant in East and southern Africa, where AIDS-related cryptococcal infections are common. Further investigations on the antimicrobial activity against a panel of bacteria causing serious infections and isolation of the active compounds are warranted. Activity-guided isolation of compounds responsible for the anti-cancer activity of the root extract seems also worthwhile.
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Correct citation of this article:
Lemmens, R.H.M.J., 2009. Terminalia sambesiaca Engl. & Diels. In: Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). Prota 7(2): Timbers/Bois d’œuvre 2. [CD-Rom]. PROTA, Wageningen, Netherlands.