Bobgunnia madagascariensis

Family

Caesalpiniaceae (Leguminosae - Caesalpinioideae)

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Chromosome number

2n = 16

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Synonyms

Swartzia madagascariensis Desv. (1826).

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Vernacular names

Snake bean tree (En). Pau ferro, pau rosa (Po). Msekeseke (Sw).

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Origin and geographic distribution

Bobgunnia madagascariensis is widely distributed in semi-arid tropical Africa, from Senegal and Gambia eastward to the Central African Republic, and south of the rainforest belt from DR Congo to Tanzania and southward to the Caprivi strip in Namibia, northern Botswana and Mozambique. It is occasionally cultivated in South Africa. In spite of its scientific name, it does not occur in Madagascar.

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Uses

The wood, traded as ‘pau ferro’, ‘kasanda’, or ‘msekeseke’, is used traditionally for poles and posts for houses, fences and kraals, and is sought after for cabinet work, musical instruments, novelties, tool handles and for carving utensils such as pestles. It is suitable for heavy construction and flooring, joinery, mine props, ship building, railway sleepers, furniture, sporting goods, toys, vats, agricultural implements, turnery and veneer. For carving it is used as a substitute for African blackwood (Dalbergia melanoxylon Guill. & Perr.). The wood is an excellent slow-burning firewood, and it is so popular for charcoal making that it is called ‘charcoal tree’ in parts of coastal Tanzania and Mozambique. Powdered heartwood soaked in hot water produces a reddish dye.
In Malawi the bark was formerly used to make bark-cloth and it provides fibre used for various purposes. When flowering the plants provide nectar for honey bees. The fruits yield a glue used to fix axe and hoe handles.
The powdered fruits, seeds and sometimes roots are widely used as poison to stupefy fish and make them easy to catch; leaves have a similar but weaker effect on fish. Powdered fruits and leaves can be used as an insecticide and insect repellent. Powdered fruits are applied in grain storage bins to protect the grain from termites and weevils. The potency of the powder on insects has also been shown on mosquito larvae. A hot-water extract can be used as insecticide for spraying around seedlings to protect them from termites. Powdered fruits and leaves are used to control slugs and snails that damage crops. Powdered fruits have been used to kill rodent pests. Bushmen people mix powdered fruits with larvae of the Bushman arrow-poison beetle (Diamphidia) to make an arrow poison. However, when fruit powder was injected subcutaneously into a cat, it produced no effect. Leaves are also used for control of bilharzia snails. The fruits are a nitrogen-rich livestock feed and cattle have been seen butting the boles of the trees to shake down the fruits, but the milk and butter from cows which have eaten the fruits is tainted. In several areas the fruits are believed to be poisonous to cattle, and Fula herdsmen prevent their cows from eating them.
Various parts of the tree are used in traditional medicine. A decoction of the fruits has been used to induce vomiting to remove poison from the stomach, and to treat bilharzia, leprosy and ear-ache. Roots are used to induce abortion, counteract venomous stings and bites, kill or expel intestinal worms and treat leprosy. A warm root infusion is used to treat venereal diseases and dysentery. Chopped roots are shaken in water which is then used to treat cataract of the eye. Roots can be taken raw as sexual stimulant. Leaves are chewed to relieve headache and used as cough medicine. A bark decoction is drunk to slow down heart palpitations in cases of extreme fatigue and to treat leprosy. A warm infusion of bark along with that of Diospyros lycioides Desf. is used to clean cuts. The bark has been used to treat diarrhoea, dysentery and as febrifuge.

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Production and international trade

The wood of Bobgunnia madagascariensis is mainly traded locally and only occasionally enters the international market. In 2003 about 2800 m³ of wood was exported from Tanzania, as short logs of 1–2 m long. The export of logs from Tanzania was permitted until mid-2004, but still 880 m³ were exported in the second half of 2005, most of it to China, at an average price of US$ 590/m³.

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Properties

The heartwood is dark reddish brown or purplish with bands varying in colour from yellow to dark brown, and clearly demarcated from the yellow, 2–3 cm wide sapwood. Growth rings form variable bands in a zigzag arrangement that makes the heartwood very decorative. The grain is wavy or interlocked, texture medium to fine and even.
The wood is very heavy, with a density of 960–1110 kg/m³ at 12% moisture content, and very hard. It dries slowly, but with only slight surface checking and end splitting. The shrinkage rates are low to moderate, from green to oven dry about 3.5% radial and 5.8% tangential. Once dry, the wood is unstable in service. Because of its extreme density and hardness, the wood is difficult to saw. It planes satisfactorily. The wood works to a fine finish and takes a high polish. Pre-boring is necessary for nailing and screwing. The wood glues and turns well. It takes vanish well, but stains do not always penetrate sufficiently. The resonance characteristics make it suitable for various musical instruments. The heartwood is very durable, being resistant to fungal, termite and borer attacks. The heartwood contains pterocarpans, a group of flavonoid phytoalexins, with powerful fungicidal properties. The compounds are related to the dyes found in the wood of Pterocarpus spp.
Several quinone-methide cassane-type diterpenes with powerful fungicidal activity, e.g. against Candida albida, have been discovered in the roots. In an assay of medicinal plants of Mali, an extract of the root bark has shown significant activity in mice against leishmaniasis. In Burkina Faso extracts of the root bark have shown some antimalarial activity. Powdered fruits contain saponins that are lethal to the freshwater snails that transmit bilharzia (schistosomiasis), and also to Cyclops, which is a host for guinea worm larvae. The saponins can be water-extracted from fruits without need for expensive equipment or highly skilled personnel. Powdered bark and chloroform or methanol extracts of the bark are effective against red flour beetle (Tribolium castaneum) in stored grain.

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Description

Semi-deciduous shrub or small tree up to 10(–15) m tall, multi-stemmed or with a single bole up to 40(–60) cm in diameter; bark surface deeply furrowed and ridged, flaking off in irregular pieces, grey-black, inner bark yellowish white, exuding a crimson-black mucilage; crown dense and rounded, with often twisted and contorted branches; twigs densely, brownish hairy. Leaves alternate, imparipinnately compound with (3–)5–9(–13) leaflets; stipules linear to narrowly ovate, 2–7 mm × 0.5–1.5 mm, persistent; petiole 2–4 cm long, rachis 5–15.5 cm long, short-hairy; petiolules 3–5 mm long; leaflets alternate, elliptical, 2–10 cm × 1–5.5 cm, increasing in size towards leaf apex, rounded at both ends, apex often slightly notched, usually hairy beneath, pinnately veined. Inflorescence a terminal or axillary raceme or fascicle up to 5(–8) cm long, 2–14-flowered, densely hairy; peduncle up to 7 cm long. Flowers bisexual, zygomorphic, sweet-scented; pedicel 0.5–5(–7) cm long; calyx irregularly 2–4-lobed; petal 1, broadly elliptical, 1.5–3.5 cm × 2–3 cm, white with grey margin and yellow patch at base inside, crinkled, with c. 0.5 cm long claw at base; stamens numerous, unequal, up to 2.5 cm long, orange-yellow; ovary superior, c. 1 cm long, glabrous, on a c. 1 cm long stipe, style short. Fruit a woody, cylindrical pod up to 20(–30) cm × 2 cm, often curved, shiny dark brown to black when ripe, indehiscent, 10–15-seeded. Seeds oblong to kidney-shaped, flattened, 7–8 mm × 5–7 mm, shiny brown or greyish. Seedling with epigeal germination.

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Other botanical information

Bobgunnia comprises 2 species and is confined to mainland tropical Africa. It has been separated from Swartzia, a genus of over 100 species in tropical America, mainly on the basis of seed characteristics, but flower structure is similar and molecular studies also point to inclusion in Swartzia.
Traditionally, Bobgunnia and Swartzia are placed in Caesalpiniaceae (Leguminosae- Caesalpinioideae), but chemistry, cytology, palynology and wood anatomy support the inclusion in Papilionaceae (Leguminosae- Papilionoideae), and this is also supported by molecular studies.

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); 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; 47: 5–20 vessels per square millimetre; 58: gums and other deposits in heartwood vessels. Tracheids and fibres: 66: non-septate fibres present; 70: fibres very thick-walled. Axial parenchyma: 78: axial parenchyma scanty paratracheal; 80: axial parenchyma aliform; (81: axial parenchyma lozenge-aliform); 82: axial parenchyma winged-aliform; 83: axial parenchyma confluent; 85: axial parenchyma bands more than three cells wide; 91: two cells per parenchyma strand; 92: four (3–4) cells per parenchyma strand. Rays: 97: ray width 1–3 cells; 104: all ray cells procumbent; 115: 4–12 rays per mm. Storied structure: 118: all rays storied; 120: axial parenchyma and/or vessel elements storied. Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells; (143: prismatic crystals in fibres).
(E. Ebanyenle, P.E. Gasson & E.A. Wheeler)

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Growth and development

Seedlings grow slowly; they are only 2.5–5 cm tall after 4 months. They reportedly often die when they have reached a height of about 30 cm. In southern Burkina Faso seedlings reached on average 53 cm tall after 30 months, and in northern Côte d’Ivoire 109 cm tall after 5.5 years with a survival rate of only 22%. In southern Africa flowering occurs together with the appearance of young leaves in September–November, sometimes continuing till January and occasionally in March–May. In Ghana flowering occurs in April–May, in Cameroon in February–April. In southern Africa, fruits mature in March–August. Seeds are released from the gummy yellow tissue inside the fruits when these have fallen to the ground and rot.

Ecology

Bobgunnia madagascariensis occurs widely scattered, but rarely abundant, in open deciduous woodland and grassland in the Sudano-Guinean savanna zone and is a characteristic tree of Brachystegia woodland in southern Africa. It is found at 150–1750 m altitude, often on sandy or clay-loam soils in valleys and flood plains.

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Propagation and planting

Propagation of Bobgunnia madagascariensis by seed is quite difficult. The weight of 1000 seeds is about 400 g. Seeds can be stored for several years with little loss of viability provided they are kept dry and insect free. Seeds germinate in 3–4 weeks. To promote germination they are best soaked in hot water for 10 minutes and allowed to cool for 24 hours. Reports on germination rates are variable. In Tanzania a germination rate of 70% in 3 weeks was reported. In Côte d’Ivoire seeds were soaked in concentrated sulphuric acid for 45 minutes and subsequently in water for 72 hours; the germination rate was 77% in 19 days. Regular cutting of the roots in the nursery increases the survival rate after transplanting, but mortality is still high.
Experiments showed that propagation by stem cuttings is possible; a concentration of 300 ppm indole-3-butyric acid showed best rooting results of the cuttings. Bobgunnia madagascariensis can also be propagated by root suckers.

Management

Bobgunnia madagascariensis responds well to coppicing and pruning.

Genetic resources and breeding

There are no indications that Bobgunnia madagascariensis is in danger of genetic erosion, because it is widespread and common throughout large parts of semi-arid tropical Africa. However, harvesting the trees for timber, firewood and charcoal, and roots and fruits for medicinal purposes is widespread throughout its range and this may make it locally vulnerable. The demand for these products is likely to increase further. The situation may be aggravated by the facts that the species grows very slowly and is difficult to cultivate, whereas procedures for its wide-scale propagation are lacking.

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Prospects

Bobgunnia madagascariensis is an important tree with multiple uses widespread in Africa. Despite its importance, there is little information on its technical wood properties and silvicultural characteristics. Therefore, research into the potential of the wood and appropriate silvicultural management systems, and the development of appropriate ways to propagate and cultivate this species are needed. The insecticidal, molluscicidal and medicinal properties of the various parts of the tree deserve further investigation.

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Major references

• Amri, E., 2011. The effect of auxins (IBA, NAA) on vegetative propagation of medicinal plant Bobgunnia madagascariensis (Desv.) J.H. Kirkbr & Wiersema. Tanzania Journal of Natural and Applied Sciences 2(2): 359–366.
• Aubréville, A., 1970. Légumineuses - Césalpinioidées (Leguminosae - Caesalpinioideae). Flore du Cameroun. Volume 9. Muséum National d’Histoire Naturelle, Paris, France. 339 pp.
• 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.
• Brenan, J.P.M., 1967. Leguminosae, subfamily Caesalpinioideae. In: Milne-Redhead, E. & Polhill, R.M. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 230 pp.
• Brummitt, R.K., Chikuni, A.C., Lock, J.M. & Polhill, R.M., 2007. Leguminosae, subfamily Caesalpinioideae. In: Timberlake, J.R., Pope, G.V., Polhill, R.M. & Martins, E.S. (Editors). Flora Zambesiaca. Volume 3, part 2. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 218 pp.
• Burkill, H.M., 1995. The useful plants of West Tropical Africa. 2nd Edition. Volume 3, Families J–L. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 857 pp.
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• Kirkbride, J.H. & Wiersema, J.H., 1997. Bobgunnia, a new African genus of the tribe Swartzieae (Fabaceae, Faboideae). Brittonia 49(1): 1–23.
• Palmer, E. & Pitman, N., 1972–1974. Trees of southern Africa, covering all known indigenous species in the Republic of South Africa, South-West Africa, Botswana, Lesotho and Swaziland. 3 volumes. Balkema, Cape Town, South Africa. 2235 pp.

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Other references

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• Borel, C. & Hostettmann, K., 1987. Molluscicidal saponins from Swartzia madagascariensis Desvaux. Helvetica Chimica Acta 70: 571–576.
• Cunningham, A.B., 1997. An Africa-wide overview of medicinal plant harvesting, conservation and health care. In: Bodeker, G. & Vantomme, P. (Editors). Medicinal plants for forest conservation and health care. Non-Wood Forest Products 11, FAO, Rome, Italy. 158 pp.
• Fanshawe, D.B., 1962. Fifty common trees of Northern Rhodesia. Lusaka, Zambia. 108 pp.
• Hepper, F.N., 1958. Papilionaceae. In: Keay, R.W.J. (Editor). Flora of West Tropical Africa. Volume 1, part 2. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 505–587.
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• Minjas, J.N. & Sarda, R.K., 1986. Laboratory observations on the toxicity of Swartzia madagascariensis (Leguminosae) to mosquito larvae. Transactions of the Royal Society of Tropical Medicine 80: 460–461.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Ross, J.H., 1977. Fabaceae, subfamily Caesalpinioideae. In: Ross, J.H. (Editor). Flora of southern Africa. Volume 16, part 2. Botanical Research Institute, Department of Agricultural Technical Services, Pretoria, South Africa. 142 pp.
• Sarda, R.K., Chhabra, S.C. & Minjas, J.N., 1986. Laboratory observations of the molluscicidal properties of Swartzia madagascariensis (Leguminosae). Journal of Ethnopharmacology 15(2): 211–213.
• Schaller, F., Rahalison, L., Islam, N., Potterat, O., Hostettmann, K., Stoeckli-Evans, H. & Mavi, S., 2000. A new potent antifungal ‘quinone methide’ diterpene with a cassane skeleton from Bobgunnia madagascariensis. Helvetica Chimica Acta 83(2): 407–413.
• Schaller, F., Wolfender, J.-L., Hostettmann, K. & Mavi, S., 2001. New antifungal ‘quinone methide’ diterpenes from Bobgunnia madagascariensis and study of their interconversion by LC/NMR. Helvetica Chimica Acta 84(1): 222–229.
• Stevenson, P.C., Nyirenda, S.P. & Veitch, N.C., 2010. Highly glycosylated flavonoids from the pods of Bobgunnia madagascariensis. Tetrahedron Letters 51(36): 4727–4730.
• Suter, R., Tanner, M., Borel, C., Hostettmann, K. & Freyvogel, T.A., 1986. Laboratory and field trials at Ifakara (Kilombero District, Tanzania) on the plant molluscicide Swartzia madagascariensis. Acta Tropica 43: 69–83.
• Thokozani, B.L.K., Zulu, D., Sileshi, G.W., Teklehaimanot, Z., Gondwe, D.S.B., Sarasan, V. & Stevenson, P., 2011. Seed germination and in vitro regeneration of the African medicinal and pesticidal plant, Bobgunnia madagascariensis. African Journal of Biotechnology 10(32): 5959–5966.

Afriref references

Sources of illustration

• Brenan, J.P.M., 1967. Leguminosae, subfamily Caesalpinioideae. In: Milne-Redhead, E. & Polhill, R.M. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 230 pp.

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Author(s)

•	W. Mojeremane Department of Crop Science and Production, Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana

Editors

•	R.H.M.J. Lemmens PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	D. Louppe CIRAD, Département Environnements et Sociétés, Cirad es-dir, Campus international de Baillarguet, TA C 105 / D (Bât. C, Bur. 113), 34398 Montpellier Cédex 5, France
•	A.A. Oteng-Amoako Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Associate editors

•	E.A. Obeng 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

Mojeremane, W., 2012. Bobgunnia madagascariensis (Desv.) J.H.Kirkbr. & Wiersema. [Internet] Record from PROTA4U. 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. <http://www.prota4u.org/search.asp>. Accessed .

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