Prota 11(1): Medicinal plants/Plantes médicinales 1
Bull. Misc. Inform. Kew 1912: 107 (1912).
Origin and geographic distribution
Plagiostyles africana occurs from Nigeria to Gabon and DR Congo.
Throughout Central Africa, a bark decoction is drunk to treat pulmonary complaints and feverish stiffness. In Gabon a wood decoction is taken to promote milk production in nursing mothers. A decoction of the fresh leaves is drunk to treat constipation. Crushed fresh leaves are applied to burns. In Congo sap from the inner bark or leaves is drunk as a purgative to expel intestinal worms in children. A leaf maceration is drunk to treat stomach spasms and heartburn. Pulverized bark with kaolin and palm oil is rubbed onto painful areas to treat side and kidney pain, headache and rheumatism. Plant sap is applied as eye drops to treat filariasis and conjunctivitis, and pounded leaves are applied to snakebites, scabies and areas of itch. Twig sap is given in water as a tranquilizer in case of fits of insanity, and is also used as a wash. In DR Congo a maceration of the inner bark is inserted into the ear to treat earache and deafness. In Gabon pounded leaves are used as fish poison. Throughout Central Africa the plant, especially the bark, is widely used in charms and religious rituals.
The wood is yellowish white and is used in Gabon to make spoons, combs and hair pins. It is suitable for flooring, poles, piles, joinery, interior trim, furniture, cabinet work, vehicle bodies, sporting goods, toys, novelties, boxes, crates, carving, turnery, veneer and plywood.
The stem bark of Plagiostyles africana contains phorbol esters. An aqueous stem bark extract showed antifungal activity against several human and plant pathogens. A methanol extract of the stem bark showed significant antimicrobial activity against several Gram-positive bacteria, but not against Gram-negative bacteria.
The heartwood is greyish brown, often with attractive dark veins and lustrous. It is more or less distinctly demarcated from the pale yellow, very wide sapwood. The grain is straight, texture fine but often uneven.
The wood is heavy, with a density of about 910 kg/m3 at 12% moisture content. It should be air dried slowly and carefully to avoid excessive splitting and warping. The rates of shrinkage are high, from green to oven dry 5.8% radial and 12.1% tangential. At 12% moisture content, the modulus of rupture is 192 N/mm2, modulus of elasticity 16,660 N/mm2, compression parallel to grain 85 N/mm2, shear 13.5 N/mm2, cleavage 27.5 N/mm2 and Chalais-Meudon hardness 7.1.
The wood saws and works well considering its density, with both hand and machine tools. It can be planed to a smooth surface and takes a high polish. The nailing and screwing properties are good. The wood is suitable for peeling and slicing. It is moderately durable and susceptible to Lyctus attack.
Dioecious, glabrous shrub or small to medium-sized tree up to 25 m tall; bole up to 80 cm in diameter, branchless for up to 12 m; bark surface brown, smooth, often with patches of horizontal ridges, with whitish latex. Leaves alternate, simple; stipules small; petiole 0.5–4(–5) cm long; blade elliptical to lanceolate, 8–20(–25) cm × 2.5–9(–10) cm, base cuneate, apex acuminate, margins undulate to shallowly toothed, shiny, pinnately veined with 7–10 pairs of lateral veins. Inflorescence an axillary raceme or panicle; male inflorescence 1–11 cm long, female inflorescence 1.5–3.5 cm long; peduncle reddish; bracts broadly ovate, c. 1 mm long. Flowers unisexual, petals absent; male flowers with pedicel 3–9(–12) mm long, calyx lobes 5–8, broadly ovate, up to 1 mm long, stamens 15–32, c. 1.5 mm long; female flowers with pedicel 1–2 mm long, enlarging to 5–10(–15) mm in fruit, calyx lobes 5, unequal, broadly ovate, up to 1 mm long, ovary superior, ellipsoid, c. 3 mm long, 1(–2)-celled, stigma almost sessile, thickened. Fruit a transversely oblong drupe c. 1.5 cm × 2.5 cm × 1.5 cm, glabrous, maturing red, finally black, 1(–2)-seeded. Seed transversely oblong, c. 1 cm × 2 cm × 1.5 cm. Seedling with epigeal germination.
In Gabon the fruits ripen in October–December. They are sweet and eaten by chimpanzees and gorillas, which may disperse the seeds.
Plagiostyles comprises a single species. It is markedly similar to the South-East Asian genus Pimelodendron.
Plagiostyles africana occurs in rainforest, commonly in secondary forest.
In many regions within its distribution area, Plagiostyles africana is quite common, e.g. in forest near Edéa (Cameroon) the average density of stems with a diameter of more than 15 cm is 0.5 per ha, with an average wood volume of 0.75 m3/ha, and in Gabon the average wood volume is 2.1 m3/ha.
Genetic resources and breeding
Plagiostyles africana is relatively frequent in its area of distribution and therefore not likely to be threatened by genetic erosion.
Plagiostyles africana is commonly used as a medicinal plant, but apart from some encouraging antifungal and antibacterial activities of the stem bark, not much is known on the chemistry or pharmacology. More research is therefore warranted to evaluate its potential to develop lead compounds for the pharmaceutical industry. Although the wood is generally not highly valued, Plagiostyles africana may have prospects for sustainable harvesting from natural forest, but research on ecology, regeneration and growth rate is needed.
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Correct citation of this article:
Schmelzer, G.H. & Lemmens, R.H.M.J., 2008. Plagiostyles africana (Müll.Arg.) Prain. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
slash and bark