Prota 11(1): Medicinal plants/Plantes médicinales 1
Taxon 9: 194 (1960).
Caesalpiniaceae (Leguminosae - Caesalpinioideae)
2n = 24, 28
Erythrophleum guineense G.Don (1832).
Forest ordeal tree, red water tree, sasswood tree (En). Bois rouge, poison d’épreuve, tali, grand tali, mancône (Fr). Mancone, muave (Po). Mwavi, mwavi dume, mbaraka mkuu, mkelekele (Sw).
Origin and geographic distribution
Erythrophleum suaveolens is distributed from Senegal to Sudan and Kenya in the east and from there south to Zimbabwe and Mozambique. It has been introduced as an ornamental in tropical Asia.
The bark, traded as ‘sassy-bark’, ‘mancona bark’ or ‘casca bark’ is used as emetic and purgative. The crushed bark is applied to swellings caused by Filaria. In DR Congo the dried powdered bark is taken as a snuff to cure headache. In Kenya a diluted decoction of the roots is used as an anthelminthic, especially against tapeworm. In Malawi a decoction of the roots and bark is applied to soothe general body pain. Pieces of root or bark are a protective and love charm. The bark has been used in arrow poisons and as ordeal poison and the bark and leaves as fish poison. The use as an anaesthetic for fish in aquaculture is tricky as small differences in dosage will kill, rather than stupefy fish. In the Western world, bark extracts were used in the late 19th century to treat heart failure. Side effects and better results with digitoxine ended this practice.
The tree produces quite hard, heavy and durable wood, marketed as ‘alui’, ‘tali’, ‘erun’, ‘missanda’ or ‘sasswood’, which is suitable for joinery, flooring, railway sleepers, harbour and dock work, turnery, construction and bridges. It is also used for boat building and wheel hubs. The bark has been used in West Africa for tanning hides and skins; it is used in DR Congo to colour leather brown. Erythrophleum suaveolens is planted as an ornamental and avenue tree. In West Africa the powdered bark is mixed with the residue of palm oil processing, and after boiling it is mixed with seeds of maize, cowpea or cotton, which effectively reduces pest damage to the seeds. Dried leaves are mixed with stored grains and pulses to repel or kill storage insects. The use in agroforestry has been promoted: nitrogen fixation and the large amount of leaf litter are advantageous to intercrops. However, in experiments a negative effect of Erythrophleum suaveolens leaf mulch on the yield of crops has been noted. When clearing bush to prepare fields, trees are often left standing because the wood is hard and felling is too taxing. Erythrophleum suaveolens wood is not highly valued as firewood but charcoal made from it is excellent.
Production and international trade
Export of bark of Erythrophleum for medicinal purposes no longer plays a role. In local markets however, the bark is an important and expensive article. In trade statistics, the timber of Erythrophleum ivorense and Erythrophleum suaveolens (Guill. & Perr.) Brenan is usually not differentiated. In 2005 the export of Erythrophleum (‘tali’) logs from Cameroon amounted to 37,500 m3 and of sawn wood to 38,600 m3, which made Erythrophleum the fourth most important timber of Cameroon. In 2005 the price of logs free-on-board was US$ 123–151/m3, depending on the quality. The major importer is China.
The alkaloid content of bark was found to range from 0.3% to 1.5%. The alkaloid content was found to vary with the age of the tree: a water extract of the bark contained 0.5% and 0.9% respectively in 60 year- and 150 year-old trees.
The alkaloid content of Erythrophleum suaveolens is similar to that of Erythrophleum ivorense; only the distribution of the main compounds is different. First investigations yielded the alkaloid erythrophleine, but this was later identified as a mixture of different alkaloids with similar activities. The alkaloids are esters of tricyclic diterpene acids, and 2 main types exist: dimethylaminoethylesters and monomethylaminoethylesters (nor-alkaloids). In addition, compounds have been found in which the amine link is replaced by an amide link, but it is not clear whether these are natural compounds or artefacts. The bark contains as main components alkaloids of the dimethylaminoethylester type: cassaine, erythrophlamine, erythrophleguine and norcassamidine as well as the amide erythrophlamide. The bark extract has excellent local anaesthetic activity on eyes and skin, although its use on the eye was disputed because of its irritant effect on the conjunctiva. Trials using it as anaesthetic in operations or tooth extractions were less successful, as symptoms of poisoning appeared in higher doses. In high doses, the bark extract is an extremely strong, rapid-acting cardiac poison, in warm-blooded animals causing shortness of breath, seizures and cardiac arrest in a few minutes.
The alkaloids have a stimulant effect on the heart similar to that of the cardenolides digitoxine (from Digitalis) and ouabain (from Strophanthus gratus (Wall. & Hook.) Baill.), but the effect is very short-lasting, as the alkaloids are rapidly metabolized in the organism. The alkaloids also have strong diuretic effects, and increase contractions of the intestine and uterus. Apart from an increase of heart contraction in systole, the alkaloids also demonstrated an increase in diastole. In addition, cassaine caused a violent state of excitation. Although the alkaloid content in the seeds is markedly lower than in the stem bark, the seeds are more toxic. This strong activity is due to a strong haemolytic saponin, which acts in a synergistic way to the alkaloids. Norcassamidine has local anaesthetic action, and is a convulsant.
The bark further contains procyanidins (polyphenols) and hence has antioxidant properties. The relaxant effect of the bark extract of Erythrophleum suaveolens is due to its procyanidins.
The bark also contains the trihydroxystilbene resveratrol. Resveratrol shows antiplatelet aggregation, coronary vasodilator, antileukaemic, antifungal and protein-tyrosine kinase inhibitory activities. Trihydroxystilbenes are thought to protect against atherosclerosis and coronary heart disease. Resveratrol is, however, only registered as a food supplement, not as a medicine. The bark contains the flavone luteolin that colours orange after addition of magnesium powder and a few drops of hydrochloric acid. This reaction allows it to be distinguished from the bark of Erythrophleum africanum (Welw. ex Benth.) Harms, which colours violet after treatment because of the presence of 2,3-dihydroxymyricetin.
Wood from Erythrophleum ivorense and Erythrophleum suaveolens is not differentiated in trade and the following wood description is applicable to both species.
The heartwood is yellowish brown to reddish brown, darkening on exposure, sometimes striped, clearly demarcated from the 3–6 cm wide, creamy-yellow sapwood. The grain is interlocked, texture coarse. The wood is moderately lustrous.
The density is about 900 kg/m3 at 12% moisture content. The wood dries slowly with high risks of distortion and checking. The shrinkage rates from green to oven dry are 5.1–5.8% radial and 8.4–8.6% tangential. Once dry, the wood is moderately stable in service.
At 12% moisture content, the modulus of rupture is 99–162 N/mm2, modulus of elasticity 10,550–19,500 N/mm2, compression parallel to grain 56–97 N/mm2 and Janka side hardness 13,000 N.
The wood is difficult to saw; satellite-tipped sawteeth are recommended. Finishing is generally fair, but planing may be difficult due to interlocked grain. Pre-boring is necessary for nails and screws. The gluing properties are good.
The wood is durable and resistant to fungi, dry wood borers and termites. It is suitable for use in contact with the ground. It is not permeable for preservatives. The sawdust may irritate mucous membranes and may cause allergy and asthma of labourers in sawmills.
Adulterations and substitutes
Erythrophleum alkaloids have similar pharmacological activities as digitoxine and ouabain. The timber from Erythrophleum suaveolens and Erythrophleum ivorense is marketed indiscriminately under the trade names ‘tali’, ‘erun’, ‘bolondo’ and ‘alui’.
Medium-sized tree up to 25(–30) m tall, often branching low; bark finely fissured, scaly, grey; twigs glabrous. Leaves alternate, bipinnately compound with 2–4 pairs of pinnae; stipules minute, soon falling; petiole and rachis up to 35 cm long, petiole thickened at base; leaflets alternate, 7–14 per pinna, ovate to ovate-elliptical, up to 9 cm × 5.5 cm, base asymmetrical, apex obtusely acuminate. Inflorescence an axillary panicle consisting of spike-like racemes up to 12 cm long, shortly yellowish hairy. Flowers bisexual, regular, 5-merous, yellowish white to greenish yellow; pedicel c. 1.5 mm long, reddish hairy; calyx lobes 1–1.5 mm long; petals 2–3 mm × 0.5 mm, short hairy at margins; stamens 10, free, c. 5 mm long; ovary superior, rusty hairy, 1-celled, stigma cup-shaped. Fruit a flat, slightly curved, dehiscent pod 5–17 cm × 3–5 cm, stipe often lateral, broadly rounded at apex, pendulous, 6–11-seeded. Seeds oblong-ellipsoid, c. 15 mm × 11 mm × 5 mm.
Other botanical information
Erythrophleum comprises about 10 species, 4 or 5 of which occur in continental Africa, 1 in Madagascar, 3 in eastern Asia, and 1 in Australia. The genus is one of the few Caesalpiniaceae reported to contain alkaloids. Erythrophleum suaveolens superficially resembles Burkea africana Hook. Mistakes in identification have led to accidental poisoning and even death.
Erythrophleum lasianthum Corbishley, the ‘Swazi ordeal tree’, closely resembles Erythrophleum suaveolens. It is restricted to the area from southern Mozambique south to Swaziland. In South Africa the powdered bark is taken as a snuff to relieve headache, as a remedy for other pains and fever, and to cure lung sickness in cattle. The bark has been used as ordeal poison in the same way as Erythrophleum suaveolens, and is also used as a fish and rat poison. The bark contains cardioactive alkaloids, mainly norcassamidine.
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; 26: intervessel pits medium (7–10 μm); (27: intervessel pits large (≥ 10 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); 58: gums and other deposits in heartwood vessels. Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 70: fibres very thick-walled. Axial parenchyma: 80: axial parenchyma aliform; 81: axial parenchyma lozenge-aliform; 83: axial parenchyma confluent; 84: axial parenchyma unilateral paratracheal; 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; 122: rays and/or axial elements irregularly storied. Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.
(E. Uetimane, H. Beeckman & P.E. Gasson)
Growth and development
Regeneration of Erythrophleum suaveolens is best in fairly open forest. Flowering has been noted to occur in January–April in West Africa, December–February in Kenya and in March–July in southern Africa. Nodulation was observed and the rhizobium involved belongs to the genus Bradyrhizobium.
Erythrophleum suaveolens occurs in moist semi-deciduous forests, gallery forest and wooded grasslands, from sea-level up to 1100 m altitude. It is absent from the evergreen forest.
Propagation and planting
Erythrophleum suaveolens can be propagated in nurseries; seed takes 3 weeks to germinate. Inoculation with Bradyrhizobium is beneficial, with increases in height and diameter of 20% and 28% respectively after 4 months.
In Sierra Leone attempts have been made to grow Erythrophleum suaveolens in plantations, but growth was slow.
The main parts of Erythrophleum suaveolens harvested for medicinal purposes are roots and bark, while the wood is exploited for timber. Traditional herbalists use ad hoc techniques to excavate the roots and debark the stems. Virtually all trees are used, from young to old ones.
Handling after harvest
Erythrophleum suaveolens roots and bark are washed and air-dried before use or trade. In Malawi sawing of the logs mainly takes place in the forest and the timber is transported to timber merchants before or after seasoning.
Erythrophleum suaveolens is widespread and locally common, and as such not threatened by genetic erosion. However, locally it is heavily exploited. One can hardly find a mature tree of Erythrophleum suaveolens that has not been debarked in Malawi and therefore it is a species of conservation concern there.
Erythrophleum suaveolens is an important medicinal plant and further study of its pharmacology is justified. Internal use of unpurified medicines made from Erythrophleum suaveolens is extremely dangerous. The difference in active ingredients between individual trees in a single population and the differences in composition related to age of the plant are not understood at all, which makes use even more hazardous. Breeding and management programmes should be started in target countries to enhance deliberate propagation and establishment in indigenous forests and plantations.
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Correct citation of this article:
Okeyo, J.M., 2006. Erythrophleum suaveolens (Guill. & Perr.) Brenan. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, branch with part of leaf and inflorescence; 2, flower; 3, pod.
Source: Flore analytique du Bénin
fruit with seeds
wood in transverse section
wood in tangential section