Aloe divaricata (PROTA)

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Plant Resources of Tropical Africa
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Aloe divaricata A.Berger


Protologue: Bot. Jahrb. Syst. 36: 64 (1905).
Family: Asphodelaceae
Chromosome number: 2n = 14

Origin and geographic distribution

Aloe divaricata is an endemic of Madagascar and is widespread in the western and southern parts of the island.

Uses

A leaf decoction of Aloe divaricata is used as a purgative. A decoction of the leaves or the leaf sap is applied internally and externally to improve healing of bone fractures. The dehydrated exudate, known as ‘Madagascar Aloes’, has been an important article in local and international trade.

Production and international trade

Export of ‘Madagascar Aloes’ by the East India Company dates back to 1630, and prices then were higher than those for ‘Socotrine aloe’, from Aloe perryi Baker. The present production is unclear and there are no export figures.

Properties

The internationally traded product ‘Madagascar Aloes’ contains 15–40% anthrone 10-C-glucosides (anthraquinone derivatives) such as aloin, hydroxyaloins and sometimes aloinoside. Aloin and aloinoside are both mixtures of stereoisomers. Aloin is responsible for the laxative properties. On a dry weight basis the exudate of Aloe divaricata contains 18.5% aloin, and the leaf 3%. Aloe divaricata is reported to induce labour by stimulating contractions of the uterine muscles.

Description

Succulent shrub, stem 2–3(–6) m tall, usually sparsely branching from the base or low down, dead leaves persistent over 50–100 cm. Leaves about 30 in a rosette, erect-spreading; stipules absent; petiole absent; blade lanceolate, up to 65 cm × 7 cm, apex obtuse, margin cartilaginous, with deltoid teeth, 5–6 mm long, reddish brown, 15–20 mm apart, blade dull grey-green tinged reddish, exudate drying yellow. Inflorescence heavily branched, consisting of 60–80 terminal, erect racemes, 15–20 cm long, lax, apex acuminate; peduncle up to 1 m long; bracts deltoid, 4 mm long. Flowers bisexual, regular, 3-merous; pedicel 6 mm long; perianth tubular, 2.5–3 cm long, up to 7 mm in diameter, lobes 6, free to base, scarlet or pale pink; stamens 6, exserted; ovary superior, 3-celled, style filiform, stigma head-like, exserted. Fruit an oblong capsule, 25–30 mm × 12 mm long, dehiscing loculicidally, many-seeded. Seeds c. 1.5 cm long, wings 4 mm wide.

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. Based on genome size, most species from Madagascar are considered closely related (with the exception of those formerly placed in Lomatophyllum) although the many different growth forms would suggest otherwise. The species from Madagascar were obviously isolated long ago from the mainland African species.

Apart from Aloe divaricata, a number of other Madagascan Aloe species have recorded medicinal uses. A number of unspecified species are used for sun creams and dandruff lotions.

Aloe vaombe

Aloe vaombe Decorse & Poiss. (orthographic variant ‘vahombe’) is a small tree with an unbranched trunk up to 5 m tall. Skin lesions are treated with leaf juice, and the leaves are boiled in water and drunk to cure yellow fever. Extracts of Aloe vaombe leaves have shown anti-infectious activity when mice were injected with them but no bactericidal activity was detected. In another test with mice, administration of a gel extract called ‘Alva’ reduced the growth rate of fibrosarcoma and melanoma tumours.

Aloe macroclada

Aloe macroclada Baker, locally called ‘vahona’, is a solitary plant without stem. The leaves are used to cure ascites, while the leaf pulp is rubbed on the head to treat dandruff. It has a reputation as a traditional anti-carcinogenic. On internet ‘vahona’ gel products are offered for sale with similar properties as for Aloe vera (L.) Burm.f.

Aloe capitata

The leaf sap of Aloe capitata Baker is used as a cathartic and purgative; the whole plant is used to cure dropsy.

Ecology

Aloe divaricata is mostly found in arid bush vegetation on sandy soils and in coastal thickets, up to 800 m altitude. In dense bush it can grow with a simple stem up to 6 m long.

Management

All Madagascan Aloe species used as medicine are collected from the wild.

Aloe divaricata is considered the Madagascan species with the highest exudate production.

Genetic resources

All Aloe species except Aloe vera are listed by CITES, and quite a number of Madagascan species appear in Appendix 1. Harvesting from the wild for medicinal and ornamental uses and habitat destruction are major threats to Aloe divaricata.

Prospects

The Aloe species from Madagascar have not been the subject of systematic ethnobotanical research. It is therefore difficult to determine their potential. Species such as Aloe divaricata, Aloe macroclada and Aloe vaombe could possibly play a role in the worldwide trade of medicinal and cosmetic products and could compete with Aloe vera if they can be cultivated and produced on a large scale.

Major references

  • CITES, 2003. Review of significant trade: East African Aloes. [Internet] http://www.cites.org/ eng/com/ PC/14/E-PC14-09-02-02-A4.pdf. May 2004.
  • Debray, M., Jacquemin, H. & Razafindrambao, R., 1971. Contribution à l’inventaire des plantes médicinales de Madagascar. Travaux et Documents No 8. ORSTOM, Paris, France. 150 pp.
  • Groom, Q.J. & Reynolds, T., 1987. Barbaloin in Aloe species. Planta Medica 53: 345–348.
  • Newton, L.E., 2001. Aloe In: Eggli, U. (Editor). Illustrated handbook of succulent plants: Monocotyledons. Springer-Verlag, Berlin, Germany. pp. 103–186.
  • Perrier de la Bâthie, H., 1938. Liliacées (Liliaceae). Flore de Madagascar et des Comores (plantes vasculaires), famille 40. Imprimerie Officielle, Tananarive, Madagascar. 147 pp.
  • Rasolondraibe, A.B., 2003. The aloes of Madagascar. Ravintsara 1(4): 16–17.

Other references

  • Radjabi-Nassab, F., Ramiliarison, C., Monneret, C. & Vilkas, E., 1984. Further studies of the glucomannan from Aloe vahombe (Liliaceae). 2. Partial hydrolyses and NMR 13C studies. Biochimie 66(7–8): 563–567.
  • Ralamboranto, L., Rakotovao, L.H., Le Deaut, J.Y., Chaussoux, D., Salomon, J.C., Fournet, B., Montreuil, J., Rakotonirina-Randriambeloma, P.J., Dulat, C. & Coulanges, P., 1982. Immunomodulating properties of an extract isolated and partially purified from Aloe Vahombe: study of antitumoral properties and contribution to the chemical nature and active principle. Archives de l’Institut Pasteur de Madagascar 50(1): 227–256.
  • Rasoanaivo, P., 1990. Rain forests of Madagascar: sources of industrial and medicinal plants. Ambio 19(8): 421–424.
  • Ravohitraniaina, H., 2003. Contribution à la valorisation de Aloe macroclada de Madagascar en cosmétique: cas des produits de soins capillaires. Mémoire de fin d’étude pour l’obtention du diplôme d’Ingénieure, Département Industrie agricole et alimentaire, ESSA, Université d’Antananarivo, Antananarivo, Madagascar. 87 pp.
  • Reynolds, G.W., 1966. The Aloes of tropical Africa and Madagascar. The Aloes Book Fund, Mbabane, Swaziland. 537 pp.
  • Stiles, D., 1998. The Mikea hunter-gatherers of southwest Madagascar: ecology and socioeconomics. African Study Monographs 19(3): 127–148.
  • Tizard, I.R. & Ramamoorthy, L., 2004. Aloes and the immune system. In: Reynolds, T. (Editor). Aloes: the genus Aloe. CRC Press, Boca Raton, Florida, United States. pp. 311–332.
  • Strickland, F.M. & Pelley, R.P., 2004. Plant saccharides and the prevention of sun-induced cancer. In: Reynolds, T. (Editor). Aloes: the genus Aloe. CRC Press, Boca Raton, Florida, United States. pp. 265–310.
  • Zonneveld, B.J.M., 2002. Genome size analysis of selected species of Aloe (Aloaceae) reveals the most primitive species and results in some new combinations. Bradleya 20: 5–12.

Author(s)

  • C.H. Bosch, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Bosch, C.H., 2006. Aloe divaricata A.Berger. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 6 February 2019.