Prota 11(1): Medicinal plants/Plantes médicinales 1
Pflanzenw. Ost-Afrikas: 140 (1895).
2n = 14
Origin and geographic distribution
Aloe lateritia is restricted to East Africa, and occurs naturally in southern Ethiopia, Kenya and Tanzania. It has not been domesticated, and is only occasionally cultivated as an ornamental. Records of Aloe lateritia for DR Congo, Rwanda, Burundi and Uganda refer to Aloe wollastonii Rendle.
In Kenya the leaf exudate of Aloe lateritia is used locally for treating colds and malaria. A decoction of the leaves is taken to treat hepatitis. In some areas leaves are applied to wounds and are used to treat chicken diseases. A liquid obtained by pounding the leaves is drunk to relieve stomach-ache. A decoction of the roots together with Solanum incanum L. roots is taken to treat anaemia. The roots are pounded, boiled and added to beer, reputedly to increase fermentation.
Two products from leaves of Aloe spp. can be used commercially in the manufacture of medicinal and cosmetic preparations. One is the gel from the centre of the leaf, the other the exudate (usually yellow) from the longitudinal vessels situated at the outer poles of the vascular bundles of the leaves. In Kenya only the exudate is harvested, as it can be processed easily into a solid material suitable for trading, and known as ‘bitters’.
The roots have been used as a dye in Kenya, giving yellow to pink-brown colours. Aloe lateritia is sometimes grown as a garden ornamental in the tropics and subtropics.
Production and international trade
In 1986 the President of Kenya announced that all Aloe species were to be protected in Kenya, and that commercial exploitation must be from plantations and not from wild plants. Although this was not formalised into law, the CITES Licensing Office in Kenya has refused since then to give export permits for Aloe plants and Aloe products. Therefore, all international trade from Kenya is illegal and no official trade figures are available. The Kenya Aloes Working Group, inaugurated in 2004, has initiated arrangements for registration of plantations developed with propagated material, and legal trading in Aloe products.
Aloe lateritia is one of the Aloe species in Kenya harvested illegally from the wild. It appears that there is substantial international trade in processed exudate, but the exported product is probably a mixture of exudate from several species. Informal figures for 2003 suggest that up to 85,000 kg of solid ‘bitters’ with a market value of about US$ 840,000 are exported from Kenya per year. Main importers are China and Saudi Arabia.
Distinctive constituents in Aloe leaves are phenolic compounds, notably chromone, anthraquinone or anthrone derivatives, but the chemistry varies considerably among species. Some of the compounds are found in many species, while others occur in only a few. From the exudate of Aloe lateritia the anthrone-C-glucosides homonataloin and aloin were isolated, both as 2 stereoisomers. Aloin is the active ingredient in the exudate and has purgative properties. Chrysophanol, asphodelin, chrysophanol-8-methyl ether, aloesaponol I, II and III and aloesaponarin I and II have been isolated from the roots. No information is available on the polysaccharides in the gel.
Adulterations and substitutes
As harvesting from the wild is uncontrolled, exudates are collected indiscriminately from many Aloe species in Kenya. Dealers buying from the collectors have not developed any method of quality control, and rely on visual assessment only.
Succulent, perennial herb, without stem or with stem up to 50 cm long, usually solitary or suckering to form small groups. Leaves 16–20 in a dense rosette; stipules absent; petiole absent; blade lanceolate, 25–50 cm × 5–10 cm, apex long-acuminate, margin with firm, brown, sharp teeth 3–4 mm long, 1–1.5 cm apart, blade fleshy, surface smooth, bright green, usually with elongated white spots in irregular transverse bands; exudate yellow. Inflorescence consisting of terminal head-like racemes 4–12 cm × 8 cm, densely flowered, sometimes to 20 cm long and more laxly flowered; peduncle up to 125 cm long, with 3–8 branches, lowest branches occasionally rebranched; bracts linear-lanceolate, 10–20(–25) mm × 4 mm. Flowers bisexual, regular, 3-merous; pedicel 2–3 cm long; perianth tubular, 3–4 cm long, inflated around the ovary, c. 5 mm diameter at the mouth, lobes 6, 10–13 mm long, orange-red, sometimes yellow, usually glossy; stamens 6, exserted; ovary superior, 3-celled, style filiform, stigma head-shaped, exserted. Fruit an ovoid capsule up to 28 mm long, pale brown, dehiscing loculicidally, many-seeded. Seeds c. 5 mm long, blackish brown, with speckled wings.
Other botanical information
Aloe comprises about 450 species in Africa and Arabia, of which c. 315 occur in mainland Africa, c. 100 are endemic to Madagascar or the Indian Ocean islands (including the former Lomatophyllum) and c. 50 occur in Arabia. The taxonomy is complicated by the occurrence of interspecific hybrids both in the wild and in cultivation. Two varieties of Aloe lateritia are recognized: var. lateritia and var. graminicola (Reynolds) S.Carter. Var. graminicola differs from the poorly suckering and strictly acaulescent var. lateritia by often having a decumbent stem up to 50 cm long, usually suckering to form dense clumps. Var. graminicola also has sharper teeth and always head-like racemes. The cuticular wax of the two taxa are indistinguishable in their chemistry and there is mention of intergrades. Var. graminicola is the more abundant of the 2 in Kenya.
Several other species that resemble Aloe lateritia in forming groups by suckering and having branched inflorescence stalks also have medicinal uses. The Topnaar people in Namibia drink an infusion of the leaves of Aloe asperifolia A.Berger to treat arteriosclerosis, kidney problems, asthma, colds and epilepsy. A decoction is taken by humans and livestock to expel the placenta, and given to donkeys when they have eaten poisonous plants. The leaves are chewed or the decoction is drunk to treat stomach-ache and chest pains. The leaf exudate is added to drinking water of chickens to treat various diseases. An infusion of the leaves of Aloe chabaudii Schönland, native of DR Congo, Tanzania and southern Africa, is taken as an abortifacient. Fatal casualties have been reported, although the abortifacient activity of the infusion could not be demonstrated in tests with rats. A decoction of the leaves is taken orally as a purgative. An infusion of the roots is taken to overcome nausea. A root decoction is drunk to treat blood in the urine. Leaf sap is rubbed into scarifications on the ankle to reduce swelling. Poultry are dipped in an infusion of the leaves to kill external parasites and the leaf juice is mixed with drinking water as a cure for poultry with blood in their faeces. Cattle are drenched with the leaf infusion to cure diarrhoea. Aloe duckeri Christian from southern Tanzania, Malawi and Zambia has been confused with Aloe lateritia but has unspotted or lightly spotted leaves and dull orange-red flowers. The leaf sap is used in southern Tanzania to help childbirth. Aloe esculenta L.C.Leach is a native of the western part of southern Africa. The leaf sap is applied to burns and cuts. The pulverized, dried root is made into a paste by adding water and is massaged into painful and swollen body parts. Aloe globuligemma Pole-Evans from Botswana, Zimbabwe and South Africa is known to have caused fatal poisoning. Plants differ in toxicity. Toxic plants smell of rats which indicate the presence of the hemlock alkaloid γ-coniceine. A leaf infusion is taken traditionally in Zimbabwe to relieve stomach-ache, as a cure for venereal diseases and as an abortifacient, although abortifacient activity of the infusion could not be demonstrated in tests with rats. Aloe hendrickxii Reynolds, an endemic of DR Congo, is used externally for healing wounds of cattle and the diluted leaf sap is applied orally to calves to cure ear problems.
Growth and development
All Aloe spp. can survive dry periods well, thus making them a useful crop for semi-arid areas; they need water though in order to develop new leaves. Seedlings take a few years before they are large enough for harvesting.
Aloe lateritia is found in grassland and open bushland, often on rocky slopes, at 250–2100 m altitude.
Propagation and planting
Aloe lateritia can be propagated by seed or by suckers. Tissue culture techniques can be used to produce large numbers of plants for establishing plantations.
Harvesting of wild Aloe lateritia is generally destructive. Development of properly managed plantations will lead to conservation of the wild populations and to substantial production. As the establishment of plantations of Aloe lateritia is just starting, there are no data on optimum spacing and general management of plantations.
Diseases and pests
Aloe spp. grown in gardens in Kenya for decorative purposes are susceptible to fungal attack, as well as scale insects and mealy bug infestation. Newly established plantations will need to be closely monitored to watch for signs of diseases and pests.
In order to harvest the exudate from Aloe lateritia leaves, a hole is dug in the ground and lined with a container, which may be a skin bag, polythene bag or plastic bowl. Leaves are cut and immediately arranged around the edge of the hole at an angle allowing the exudate to drain into the container. When no more sap is seen to be dripping from the leaves, the exudate is transferred to bottles or jerry cans for sale to a dealer.
Harvesting of exudate of Aloe lateritia takes place throughout the year, though it has been observed that the yield is higher during rainy seasons. On average one mature plant can produce 80–100 ml of exudate. In some areas of Kenya dealers obtain up to 1700 l/day from collectors.
Handling after harvest
Dealers only visually inspect the quality of the exudate. The usual reason for rejection of the exudates is that the liquid is too thin or ‘watery’, as seen from the ease with which a small sample will soak into the ground. The dealer will store the exudate until at least 200 l has accumulated before further processing. The liquid is placed in a large drum and boiled over a controlled fire for a period of 5–11 hours, depending on the quality. Eventually the exudate becomes black and very viscous. It is then removed from the fire and transferred from the drum to sacks, in which it is left to cool and harden. After a day the material is solid and black, called ‘bitters’, and is ready for sale to a middleman, who will sell it on to an exporter. Because of the illegality in Kenya, the whole marketing chain is shrouded in secrecy.
Aloe lateritia is collected indiscriminately from the wild, with no selection factors involved. The few plantations now being established are stocked with plants (probably from various species) collected in the wild. All Aloe, except Aloe vera (L.) Burm.f., are protected by CITES and all international trade of plants and products should be regulated.
So far there has been no attempt to improve the stock of Aloe lateritia by breeding but there is ample scope for selection in this highly variable species.
The yield of exudate of Aloe lateritia is not as high as in other species currently being harvested, and it is possible that other species will be preferred when plantations are developed.
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Sources of illustration
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Correct citation of this article:
Newton, L.E., 2006. Aloe lateritia Engl. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, plant habit; 2, part of inflorescence.
Redrawn and adapted by Achmad Satiri Nurhaman
flowering plant habit