Euphorbia tirucalli (PROTA)
|Geographic coverage Africa|
|Geographic coverage World|
|Essential oil / exudate|
|Forage / feed|
- Protologue: Sp. pl. 1: 452 (1753).
- Family: Euphorbiaceae
- Chromosome number: 2n = 10, 20
- Euphorbia laro Drake (1899).
- Finger tree, finger euphorbia, petroleum plant, pencil tree, rubber hedge euphorbia, rubber euphorbia, African milkbush (En).
- Euphorbe effilée, tirucalli (Fr).
- Almeidinha (dried latex), cassoneira, aveloz, euforbia (Po).
- Mtupa mwitu, malangili, mwasi, mchakaazi, mtovua macho (Sw).
Origin and geographic distribution
Euphorbia tirucalli originates in eastern tropical Africa, and has long since become naturalized in other parts of Africa, including South Africa and the Indian Ocean islands. It is widely naturalized and planted as an ornamental throughout the tropics and subtropics and is grown as a pot plant in temperate regions.
In Africa including Madagascar the latex of Euphorbia tirucalli is used for its potent purgative and emetic properties to treat stomach complaints, constipation, intestinal worms, headache, asthma, epilepsy, palpitations, poisoning and snakebites. A few drops of latex are reportedly sufficient to cause vomiting, and are taken in milk as an antidote to poisoning or snakebites. Anecdotal evidence suggests that the risks of a lethal overdose are high, particularly when treating children. The latex has severely irritant effects on the skin and mucosa. It causes painful blistering and inflammation, and may cause blindness if it comes into contact with the eyes. Heated branches are chewed and the latex is swallowed to relieve a sore throat and dry cough, but also to induce labour during childbirth. The latex is externally applied to warts, wounds, skin complaints, swollen glands, oedema, haemorrhoids, rheumatism, toothache, earache and tumours. In Brazil the latex is widely used to treat cancer, but in some areas where it is commonly used, tumours of the nose are prevalent and thought to be related to this use. The roots of Euphorbia tirucalli are widely taken alone or in a mixture to treat schistosomiasis and sexually transmitted diseases. In Mauritius a root and bud decoction is taken as a laxative, and to treat coughs and pectoral pain. Ash from burned branches and stems is used to treat whooping cough and is externally applied as a caustic to open abscesses. Pulped twigs are applied to oedema of the legs.
The latex is taken in therapy of sexual impotence and sterility in East Africa, and elsewhere as a sexual stimulant, and it is also said to promote breast enlargement. In East Africa the latex is commonly used as arrow poison and as an ingredient for bait to kill rodents and other wild animals; the pulped stems are thrown in water as fish poison. In south-western DR Congo the latex has been used in high doses as a trial by ordeal poison; in various countries it is used as criminal poison. The latex is also used as a fly repellent in West Africa and a mosquito and termite repellent in Tanzania. In India the latex is used as an insecticide.
Goats and sheep browse the green parts of the plant. The toxicity of the latex is considered seasonal or reduced in young plant parts, and young branches are even roasted and chewed. Euphorbia tirucalli is widely planted as an ornamental in gardens and as a pot plant, and a golden-stemmed cultivar exists. It is widely cultivated as a hedge and around cattle enclosures, as it is considered impenetrable, due to the poisonous latex and dense growth; it is also planted as a firebreak and boundary marker. The plants are used to control soil erosion, to stabilize sand dunes, and, in some parts of Africa, as grave-markers. In agriculture Euphorbia tirucalli is used for mulch and as pesticide. It is unsuitable for intercropping as the plants suppress undergrowth, including crops. In South Africa it is reported to keep moles away. The white wood is used to make rafters, granary floors, house posts, toys and veneer. It is also used as firewood when no other fuel is available. Gunpowder for fireworks has been produced from the charcoal. The latex is a source of natural rubber, but its resin content is too high for economic use. Resin from the latex appeared useful for application in linoleum, oilskin and leather cloth industries, but is not durable as a varnish. Biomass can be converted into gas, liquid fuels and solid fuels such as pellets, briquettes and charcoal. The latex has strong fixative properties and is used in coastal East Africa to fix knife-blades to wooden handles and spear-heads to shafts. In Malawi the latex is used as bird lime to trap birds. Zulu warriors used it to make headdresses. In Gabon and the Seychelles Euphorbia tirucalli is planted in villages as a medico-magical plant.
Production and international trade
In the 1980s Euphorbia tirucalli was planted in Senegal, East Africa, Brazil and Japan as a potential energy crop; later trials concentrated on biogas production, but no recent information is available. Euphorbia tirucalli is widely traded on the internet as an ornamental.
The chemical composition of Euphorbia tirucalli has been subject to many investigations, and from all plant parts a wide range of diterpene esters has been isolated. These diterpenes are of the tigliane, ingenane and daphnane types, and are based on the parent alcohols ingenol, phorbol, resiniferonol, 12-deoxyphorbol and the rare 4-deoxyphorbol and 12-deoxy-4β-hydroxyphorbol. The latex is an emulsion of about 30% terpenes in water. Several chemical races exist with different diterpene profiles, e.g. from East Africa, Madagascar, South Africa, India and South America. Samples of latex from South Africa and Colombia, for instance, contained predominantly irritant and tumour-promoting esters of 4-deoxyphorbol and highly unsaturated aliphatic acids. The main irritants in samples from Madagascar were 3-acylates of ingenol and di-esters of phorbol containing an acetate group and a long-chain highly unsaturated acyl group. The acyl groups were similar to those in latex from South Africa, while esters of 4-deoxyphorbol were completely absent from the Madagascan material. Latex from greenhouse plants in Germany did not contain tigliane- or ingenane-type diterpene esters and did not exhibit irritant activity.
Other terpenes isolated from latex of different origins are the diterpenes euphol and its stereoisomer tirucallol, the highly toxic daphnane diterpene ester tinyatoxin, the triterpenoids euphorbinol, cycloeuphorbinol, euphorone and the 31-nortriterpene cycloeuphordenol and the macrocyclic diterpene tirucalicine. The latex also contains an isoquinoline alkaloid as well as the sterols taraxasterol, phorbosterol, euphorbosterol, α-amyrine and cycloartenol. Four trypsine-like proteolytic enzymes, euphorbains t1–t4, have also been isolated. The twigs have yielded taraxasterol, β-sitosterol, ellagic acid, kaempferol, glucose and the hydrocarbon hentriacontane, as well as an alcoholic analogue. The whole plant contains 7.4% citric acid with some malonic and succinic acid. The stem bark yielded the following compounds: cycloartenol, 24-methylene cycloartenol, β-sitosterol, α-taraxerol, euphorbol, euphorbol-hexacosonoate, taraxerone as well as diterpene esters, including ingenol triacetate, the pentacyclic triterpene euphorcinol and the taraxerane type triterpene euphorginol. Several diterpene esters, tiglianes and daphnanes have been isolated from the roots, based on 12-deoxyphorbol, 12-deoxy-16-hydroxyphorbol and resiniferol, including tinyatoxin and candletoxin A. Two anthocyanins were also isolated from the roots.
A biopolymeric fraction of the aerial parts showed dose dependent anti-arthritic activity in vitro and also showed immunomodulatory capacity in both rats and mice. The LD50 in healthy mice and rats exceeded 2000 mg/kg. In-vivo mammal bioassays have demonstrated dose-dependent anti-inflammatory activity of aqueous extracts, which inhibited oedema by up to 68%.
Euphorbia tirucalli is a cause of Burkitt’s lymphoma, a highly aggressive tumour endemic to children in the Central African Region, where Euphorbia tirucalli is widely used in traditional medicine. The epidemiology of Burkitt’s lymphoma is unclear, but has been associated with plant species such as Euphorbia tirucalli and Jatropha curcas L., as well as with malaria and Epstein-Barr virus (EBV); these associations are generally weak in areas of low incidence. The diterpene esters from the latex of Euphorbia tirucalli activate latent EBV within a cell, and a plant extract induces continuous mitosis and chromosomal rearrangements in EBV infected B-lymphocytes in vitro. The cocarcinogenic compound, a 4β-deoxyphorbol ester isolated from the latex, was found to reduce the EBV-specific cytotoxic T-cell function. These activities of the 4β-deoxyphorbol ester suggest that it plays a role in the modification of human retroviral infections in vivo, including AIDS and human T-cell leukaemia virus type 1 (HTLV-1) associated diseases. An ethanol extract of the dried aerial parts given orally to tumour-bearing mice showed myelosuppression in bone marrow and enhanced resistance by significantly reducing tumour growth in the peritoneal cavity.
Extracts of Euphorbia tirucalli have exhibited in vitro antimicrobial activity against gram-negative and gram-positive bacteria, certain fungal plant pathogens, and the Herpes simplex virus, the latter in the absence of cytotoxicity (therapeutic index >7.1). An aqueous extract also showed significant antibacterial activity against the crop pathogens Erwinia carotovora, Xanthomonas campestris and Pseudomonas solanacearum. Extracts of the latex and stem bark have shown larvicidal activity against larvae of the mosquito Culex quinquefasciatus, nematicidal effects against the parasitic nematode Heterodera cajani and also against Hoplolaimus indicus, Helicotylenchus indicus and Tylenchus filiformis in vitro. The aqueous latex extracts showed significant molluscicidal activity against the freshwater snails Lymnaea acuminata, Lymnaea natalensis, Biomphalaria glabrata and Bulinus guernei.
Rubber produced from the latex of Euphorbia tirucalli is limited in quality by its high resin content, which can be up to 82%. The rubber content of the latex is very variable; fresh latex contains on average 13% rubber, but may be as low as 1.6%.
Euphorbia tirucalli may become an important biofuel plant. Initial attention focussed on the latex for the conversion of the terpenoids into biopetrol. However, experimental plantations for biopetrol production were not economically viable, as the production cost per barrel of oil was estimated to be between US$ 150 and US$ 200. Attention later shifted to the conversion of the whole biomass into methane.
Estimates of the gross energy value of Euphorbia tirucalli dry biomass range from 15,900 kJ/kg to 17,600 kJ/kg, fresh material containing about 85% water. Fermentation of chopped, fresh aerial parts gives yields of biogas comparable to other agro-industrial wastes. Euphorbia tirucalli could be an appropriate plant for methane production in the Sahel where food crops do not yield well, since it is well adapted to poor soils. In other experiments, Euphorbia tirucalli stems increased yields of biogas from fermented cattle manure. Optimal methanization occurs on freshly chopped material at about 48°C.
The latex shows similarity in composition and activity to the highly poisonous croton seed oil from Croton tiglium L. When ingested, the latex causes congestion in the stomach, intestines, kidneys and spleen. A 400 μl dose of diluted latex given to rats is sufficiently potent to cause stomach perforation and death. Doses of up to 30 g/kg fresh Euphorbia tirucalli fed to cattle reportedly cause mild symptoms of poisoning. Neither genotoxic nor anti-genotoxic effects were established in tests of aqueous latex solutions using the fruitfly Drosophila melanogaster.
Euphol is present in large amounts in the latex, but tirucallol predominated in greater quantities in explants and callus cultures indicating synthesis and/or accumulation of tirucallol by cells other than the laticifer cell. Sterol production was significantly enhanced by certain nutrient media, as well as indole-3-acetic acid, and depressed by benzyladenine.
The wood is pale, hard and with a fine texture, and is rarely attacked by insects.
Succulent, much-branched, monoecious or more often dioecious shrub to 4 m tall or small tree up to 10(–15) m tall; branchlets rounded, c. 7 mm in diameter, often produced in whorls, brittle, green with longitudinal fine stripes and very small leaf scars, the extreme tips of young leafy branchlets sparsely short-hairy, with copious white to yellowish latex. Leaves arranged spirally, present only at the tips of young branchlets and quickly falling, simple and entire, almost sessile; stipules minute, glandular, dark brown; blade linear-lanceolate, c. 15 mm × 2 mm, fleshy. Inflorescence a terminal umbel-like cyme, 2–6 together at the apex of branchlets, each forking 2–4 times, composed of dense clusters of flowers, each cluster called a ‘cyathium’, developing only male flowers (sometimes with a few female flowers), or only female flowers; bracts c. 2 mm long, rounded; cyathia almost sessile, c. 3 mm × 4 mm, involucre cup-shaped, glands 5, up to 1.5 mm × 2 mm, bright yellow, lobes triangular, c. 0.5 mm long. Flowers unisexual; male flowers with linear bracteoles, plumose at apex, stamen c. 4.5 mm long; female flowers with small bracteoles, pedicel up to 10 mm long in fruit, hairy, perianth distinctly 3-lobed, lobes c. 0.5 mm long, ovary superior, 3-celled, styles c. 2 mm long, fused at base, with thickened deeply bifid recurved stigma. Fruit a nearly globose capsule c. 8 mm × 8.5 mm, almost glabrous, 3-seeded. Seeds ovoid, c. 3.5 mm × 3 mm, smooth, speckled with brown and with a dark brown ventral line; caruncle 1 mm across.
Other botanical information
Euphorbia comprises about 2000 species and has a worldwide distribution, with at least 750 species occurring in continental Africa and about 150 in Madagascar and the Indian Ocean islands. Euphorbia tirucalli belongs to section Tirucalli, a group which is characterized by cylindrical, succulent branches with copious latex, small, quickly falling leaves, cyathia in terminal umbel-like cymes, 5 glands, an exserted fruit and seeds with a caruncle. The species mentioned below also belong to this section.
Euphorbia damarana L.C.Leach is endemic to Namibia; the toxic latex is used to pollute water holes to poison and catch game drinking from them. The latex is highly irritating to the skin and mucous membranes.
Euphorbia gossypina Pax occurs from Somalia south to Zimbabwe. In Kenya a decoction of the pounded stems is drunk to treat swollen legs and general body pain. In Tanzania the latex is applied as eye drops to treat conjunctivitis, as ear drops to treat oral infections and also to warts that have first been cut open. The diluted latex of small twigs is taken to treat laryngitis. In Somalia the latex is applied to mange in livestock.
Euphorbia spartaria N.E.Br. is endemic to Namibia; the latex is applied to warts.
Growth and development
Euphorbia tirucalli is a rare example of a species in which the physiological mechanisms of Crassulacean Acid Metabolism (CAM) in the stems are combined with C3 photosynthesis in the leaves. Other adaptations to drought include succulent stems and sunken stomata. Salt tolerance in Euphorbia tirucalli is attributed to adaptations that limit the uptake of salt ions by the roots, and store the ions in the roots and stems. Euphorbia tirucalli grows vigorously once established. Leaves are only present during the rainy season and flowering starts at the end of the dry season before new leaves are formed. Pollination is by insects.
Euphorbia tirucalli is very well adapted to semi-arid conditions, but also occurs in both dry and moist forest, savanna and shrub land, and withstands salt stress associated with coastal conditions, but no frost. It occurs from sea-level up to 2500 m altitude. It grows well on a wide variety of light-textured, neutral to acidic soils. It is commonly associated with human settlements and becomes naturalized rapidly. It is locally common and often occurs in groups.
Propagation and planting
Euphorbia tirucalli is sometimes propagated by seed, but usually by stem or root cuttings, and establishes quickly on almost any soil. Cuttings should be at least 10 cm long and should be left to dry for at least 24 hours before planting. For ornamental purposes, cuttings of 35–40 cm long are usually taken and for hedges cuttings of up to 1 m long. Euphorbia tirucalli can also be propagated through micro-propagation.
When grown as a fuel crop, cuttings can be planted very densely depending on the climatic and edaphic conditions, at 10,000–20,000 plants/ha. In Kenya freshly planted cuttings are protected from browsing and sun by Acacia branches. Planting can start at the beginning of the rainy season. Weeding is necessary only as seedlings become established; later, weeds are suppressed by litter from the crop.
Euphorbia tirucalli may be coppiced, trimmed and top-pruned to establish a living fence or hedge. As it is well adapted to semi-arid conditions and can be grown on marginal land, plantations were established for use as energy crop. Application of single-nutrient or compound fertilizer results in increased growth. In Zimbabwe, plantations of Euphorbia tirucalli have succeeded in some instances on the spoil mounds of arsenic mines.
Diseases and pests
In India several diseases occur including stem rot caused by Phoma sorghina and necrotic spots by Alternaria sp.; Nectria euphorbiana was found on dead stem material. In Pakistan Euphorbia tirucalli is a host of Botryodiplodia theobromae and also of Cuscuta spp. Euphorbia tirucalli can be severely affected by nematodes, including Meloidogyne spp. Aphids, mealy bugs and grasshoppers feed on the plants, whereas mites occur on leaves and young growth, especially in greenhouses.
Branches of Euphorbia tirucalli can be cut for medicinal use whenever the need arises. In biofuel plantations the plants can be cut at 20–30 cm above the ground.
Yield of Euphorbia tirucalli stems for biofuel production varies greatly with density of planting, number of cuttings per year, annual rainfall and soil type. In Thailand yields varied between 150 t/ha fresh weight and 2.3 t/ha dry weight for high-density plots (10,000 plants/ha) with 6 harvests, and 25.5 t/ha fresh weight for low density plots (1600 plants/ha) with one harvest.
In biogas production, the low N content and easily decomposed stem pieces of Euphorbia tirucalli result in high methane output rates. In an experiment in India, 375 g fresh stem cuttings and 375 g fresh cattle manure were fermented in 750 ml water and yielded 19.2 l gas. A field producing 500 t/ha/y of biomass would result in 137 kg/dry matter/day and 31 m3 methane per day or about 20 kg methane per day.
Handling after harvest
In medicine, the harvested parts of Euphorbia tirucalli are usually used fresh.
Euphorbia tirucalli is widely planted and naturalized and is therefore not threatened by genetic erosion. As a succulent Euphorbia species, its trade is controlled under CITES appendix 2.
Euphorbia tirucalli is an important multi-purpose plant. It has many medicinal uses, which are partly confirmed by pharmacological tests. As the latex has tumour-promoting properties and is implicated in the epidemiology of Burkitt’s lymphoma, its use in traditional medicine should be discouraged. Further research is warranted to clarify its antibacterial and anti-arthritic activities.
Euphorbia tirucalli is a unique example of a plant combining permanent crassulacean acid metabolism (CAM) stems with short-lived C3 leaves. During humid spells when leaves are present, this combination allows high CO2 uptake and, thus, elevated growth rates. It is a low-input plant, with high drought and salinity stress tolerance that can be grown on land that is not suitable for crops. It has the potential to provide semi-arid zone inhabitants with an energy solution in the form of a biomass that can be converted to gaseous, liquid or solid biofuels. More research is needed and should cover crop genetic improvement, improved farming techniques to intensify production, improve the product quality, and develop efficient technologies to extract and use the biofuels.
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Sources of illustration
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Correct citation of this article
Grace, O.M., 2008. Euphorbia tirucalli L. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 14 July 2021.
- See the Prota4U database.