Prota 2: Vegetables/Légumes
Fl. Oware 1: 16, t. 11, 12 (1805).
Cecropiaceae (APG: Urticaceae)
2n = 28
Giant yellow mulberry, bush pineapple, corkwood (En). Grand wounian, arbre à pain indigène (Fr). Pernambuco (Po).
Origin and geographic distribution
Myrianthus arboreus occurs in the forest zone of tropical Africa from Guinea and Sierra Leone east to southern Sudan and Ethiopia and south to DR Congo, Tanzania and Angola.
In West Africa young leaves are eaten in vegetable soups. In Delta and Edo States of Nigeria, the leaves of Myrianthus arboreus are rated among the most popular indigenous vegetables. Throughout the range of the species, the heartshaped fruit, called ‘God’s heart’ in Ghana, is eaten for its sweet or acidulous pulp. The oil-rich seed, which is about 1 cm long, is eaten after cooking from Côte d’Ivoire to DR Congo.
Extracts of the leaves or leafy shoots of Myrianthus arboreus are used in Sierra Leone, Nigeria and the Mount Cameroon area in preparations to treat dysentery, diarrhoea and vomiting. In the Igala area of Nigeria the leaves are an ingredient of a febrifuge given to young children. In eastern Nigeria a plaster made of beaten leaf-petioles is applied to boils, and the bruised leaf is similarly used in Gabon. In Congo chopped leaves are eaten raw with salt to treat heart troubles, pregnancy complications, dysmenorrhoea and incipient hernia. A bark decoction is drunk to treat malaria, fever and cough. In DR Congo a leaf decoction is also used as an anticough medicine. In Tanzania an infusion of the leaves is taken to improve lactation in women. Sap from young leaves or terminal buds is applied topically to treat toothache or to the chest against bronchitis and to the throat against laryngitis or sore throat. Myrianthus arboreus is a useful analgesic in the treatment of muscular pains, fractures and haemorrhoids. In Côte d’Ivoire pounded leaves are applied as an enema to treat pain in the back and loins. The copious sap from the aerial roots is drunk in Congo as an antitussive and antidiarrhoeic, and as a remedy for haematuria and blennorrhoea. The roots are diced and prepared together with melegueta pepper (seeds of Aframomum melegueta K.Schum.) as a vapour bath against headache. In Congo the whole fruit is boiled in sap from the tree or in palm wine or other fruit-ferments and taken as an emeto-purgative; the bark or leaves are used similarly but are considered less effective. Myrianthus arboreus is important as an auxiliary plant, the leaves forming a thick layer of organic mulch. It is being tested for managed fallow systems.
The wood is soft, yellowish white, perishable and difficult to work, but is used for fencing and occasionally as a general purpose wood. The wood is also suitable for paper making. Its ashes are used in soap making in Guinea. Extracts of Myrianthus arboreus deter the termite Reticulitermes lucifugus.
Production and international trade
No production data on Myrianthus arboreus are available. The leaves are locally traded. Export trade of the leaves is not reported, but several firms are licensed to export material of Myrianthus arboreus for pharmaceutical purposes.
There is no information on leaf composition. The composition of fresh fruit pulp of Myrianthus sp. per 100 g edible portion is: water 85.5 g, energy 205 kJ (49 kcal), protein 1.9 g, carbohydrate 11.8 g, Ca 44 mg, P 70 mg, Fe 1.1 mg. The composition of dried seeds per 100 g is: water 13.5 g, energy 1972 kJ (471 kcal), protein 23.6 g, fat 33.4 g, carbohydrate 27.0 g, fibre 3.5 g, Ca 132 mg, P 371 mg, Fe 6.6 mg (Leung, W.T.W., Busson, F. & Jardin, C., 1986). The oil consists almost exclusively of linoleic acid (93%). The protein is rich in the amino acid cystine which is important in a region where chronic deficiency of sulphur-bearing amino-acids occurs.
Several pentacyclic triterpenoids have been isolated from the wood and the roots. Euscaphic acid, myrianthic acid, tormentic acid, ursolic acid and a derivative of ursenoic acid have been isolated from stems. Myrianthinic acid was isolated from the bark. The wood also contains myrianthiphyllin, a lignan cinnamate.
Bark extracts of Myrianthus arboreus showed antiplasmodial, antimycobacterial and antitrypanosomal effects in vitro, which supports some of its uses in traditional medicine, e.g. to treat malaria.
Dioecious shrub or tree up to 14(–20) m tall; bole short, up to 1 m in diameter, often with stilt roots; bark fairly smooth, greyish, thin, slash white; branches spreading. Leaves arranged spirally, palmately compound; stipules up to 5 cm long, amplexicaul, caducous, leaving annular scars; petiole (15–)25–55 cm long; leaflets 5–7, sessile or stalked, lanceolate or oblanceolate, up to 65 cm × 22 cm, margin serrate to dentate, whitish pubescent on veins below, many-veined. Male inflorescences repeatedly branched, up to 30 cm in diameter, consisting of glomerules, with peduncle up to 20 cm long; female inflorescences a globose head up to 3.5 cm in diameter, with peduncle up to 6 cm long. Flowers sessile, small; male flowers with 3–4 tepals and 3–4 stamens; female flowers with 2–3-lobed perianth and superior, 1-celled ovary, stigma tongue-shaped. Fruit drupe-like, with fleshy perianth, yellow to orange-red, 1-seeded, closely arranged in an infructescence up to 10(–15) cm in diameter. Seed up to 12 mm long. Seedling with simple leaves.
Other botanical information
Myrianthus comprises 7 species and is restricted to tropical Africa. The lowlands of West and Central Africa are richest in species. The leaves of Myrianthus libericus Rendle and Myrianthus serratus (Trécul) Benth. & Hook. are also occasionally collected as a vegetable, but their edible fruits and seeds seem to be more important as they are for other Myrianthus species. The East African Myrianthus holstii Engl. is related to Myrianthus arboreus, but can be distinguished by its yellow to orange -brown indumentum.
Growth and development
The seeds of Myrianthus arboreus are dispersed by animals such as monkeys and birds. Natural regeneration also takes place around the base of trees in forests as well as farmland. During forest clearing for farming, Myrianthus arboreus trees are often protected and retained. In an experiment trees started bearing fruit when about 5 years old. In West Africa the trees flower from January to April and bear fruits from February to July, whereas in Central Africa they can be found flowering throughout the year and in Tanzania they flower from November to December and fruits mature from February to March.
Myrianthus arboreus is a common tree in the forest area of West and Central Africa, occurring in rain forest, semi-deciduous forest, swamp forest, also as a late pioneer species in secondary forest and fallow land, in wet or damp situations and on stream banks. It needs a high annual rainfall. It grows naturally from sea-level up to 1200 m altitude. In Nigeria it is common in the lowland, below 300 m altitude.
Myrianthus arboreus leaves are collected from wild and semi-wild stands. Protection and retention of trees in farms is common. It is recommended as a fallow species for more remote fields. Through its mycorrhizal associations it has the ability to improve the nitrogen status of the soil.
Propagation and planting
Germination of the seeds takes about 1 month; the germination rate is about 40%, but can be improved by soaking the seed prior to planting. Bud grafting and stem cuttings have been successfully used for propagation in experiments.
Young tender leaves are plucked when required. A market survey in Enugu (south -eastern Nigeria) indicated availability during February–October. In Tanzania the fruits are picked early in the dry season.
Handling after harvest
The leaves of Myrianthus arboreus remain fresh for 3–5 days; leafy twigs are brought to the local market soon after harvesting.
The genetic diversity in Myrianthus arboreus has not been studied, but there are no indications that serious genetic erosion occurs.
The leaves and fruits of Myrianthus arboreus provide food, especially important during the hunger period before the harvest of other crops. Its myriad medicinal uses indicate that more research into its chemical composition and pharmacological activities is justified.
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Sources of illustration
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Correct citation of this article:
Okafor, J.C., 2004. Myrianthus arboreus P.Beauv. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, bole; 2, leaf; 3, infructescence.
Redrawn and adapted by Achmad Satiri Nurhaman