Agave americana (PROTA)

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Plant Resources of Tropical Africa
Introduction
List of species


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Agave americana L.


Protologue: Sp. pl. 1: 323 (1753).
Family: Agavaceae
Chromosome number: 2n = 60

Vernacular names

  • Century plant, American agave, American aloe (En).
  • Agave d’Amérique (Fr).
  • Piteira de boi, piteira brava (Po).

Origin and geographic distribution

Agave americana is a native of Mexico and the southern United States. It has been distributed throughout the world for its ornamental value. Its distribution in Africa is not reflected by collections in herbaria as it is introduced and not easy to collect. However, it is probably found throughout tropical Africa.

Uses

In DR Congo and Mauritius the leaf sap of Agave americana is drunk for its laxative and diuretic properties and as an emmenagogue. It is applied to wounds and cuts to promote healing. A decoction of the roots is taken, mixed with honey, to cure syphilis and it also has diuretic properties. In South Africa the leaves are used to treat cardiac problems, high blood pressure and gastro-intestinal problems. The leaves are split, heated and applied externally to relieve rheumatic pain. The leaf sap is used as an insecticide, e.g. against termites in Tanzania.

As an ornamental, Agave americana is planted in private and public gardens and on roadsides. It is used as a hedge plant and planted along contours for erosion control and for reclamation of denuded and overgrazed land. The leaf fibres are used locally to make textiles.

Properties

Two different derivatives of triacontanol, isolated from the leaves, were shown to have antibacterial activity against Staphylococcus spp., Pseudomonas aeruginosa and Escherichia coli. Leaf extracts showed molluscicidal and insecticidal properties. The leaves contain angiotensin-converting enzymes that are a potent medicine to treat hypertension. The leaves also contains several sapogenins, e.g. hecogenin, which can be used in the manufacture of semisynthetic corticosteroids, but only if they do not contain too much tigogenin, because this results in losses in product quality and yield. In Nigerian plants tigogenin was only found in trace amounts in the leaves. Tigogenin itself is a base material for the production of other steroids.

The leaves contain needle-like calcium oxalate crystals, called raphides, which can cause contact dermatitis and conjunctivitis.

Description

Robust, perennial herb up to 9 m tall when flowering, producing suckers; stem short and thick, up to 20 cm in diameter, with a dense rosette of leaves at apex. Leaves arranged spirally, succulent, sessile, lanceolate, 1–2 m × 15–25 cm, base fleshy, triangular in cross section, apex with sharp, dark brown spine up to 5 cm long, margin wavy to toothed with teeth up to 10 mm long, pale blue-grey to green, sometimes variegated. Inflorescence a very large, terminal, rather open panicle; peduncle 2–8 m long. Flowers bisexual, regular; perianth tubular, 8–20 mm long, 6-lobed, pale yellow; stamens 6, attached above the middle of the perianth tube, 6–9 cm long; ovary inferior, 3-celled, style 1, longer than the stamens, stigma 3-lobed. Fruit an oblong capsule 4–5 cm long, shortly beaked, many-seeded. Seeds flat, disk-shaped, 7–8 mm × 5–6 mm, curved, shiny black. Seedling with epigeal germination.

Other botanical information

Agave americana follows the Crassulacean Acid Metabolism (CAM) pathway. CAM plants are able to fix CO2 at night and photosynthesize with closed stomata during the day, thus minimizing water loss. Agave comprises 100–200 species, all native to Central America and Mexico.

Ecology

Agave americana is adapted to a wide range of conditions. In East Africa it is found from sea-level to 2500 m altitude. It is found in both low and high rainfall areas. In many countries in southern Africa, including South Africa, it is considered a noxious invasive weed.

Management

Multiplication of Agave americana is done by suckers or seeds. The hecogenin content of the leaves increases with age of the plant and is highest during dry periods.

Genetic resources

As Agave americana is widely distributed and cultivated no threats are envisaged. Many ornamental cultivars have been developed, including a cultivar with pale yellow leaf margins, known as ‘Marginata’, which is widely planted. Breeding and selection for ornamental properties is ongoing.

Prospects

As a source of medicine for hypertension, Agave americana is promising. Hypertension, often regarded as a disease of well-to-do populations, is on the increase in urban populations in Africa.

Major references

  • Duncan, A.C., Jäger, A.K., & van Staden, J., 1999. Screening of Zulu medicinal plants for angiotensin converting enzyme inhibitors. Journal of Ethnopharmacology 68: 63–70.
  • Edwards, S. & Tesfaye, Y., 1997. Agavaceae. In: Edwards, S., Mesfin Tadesse, Demissew Sebsebe & Hedberg, I. (Editors). Flora of Ethiopia and Eritrea. Volume 6. Hydrocharitaceae to Arecaceae. The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. pp. 83–85.
  • Gelfand, M., Mavi, S., Drummond, R.B. & Ndemera, B., 1985. The traditional medical practitioner in Zimbabwe: his principles of practice and pharmacopoeia. Mambo Press, Gweru, Zimbabwe. 411 pp.
  • Gurib-Fakim, A., Guého, J. & Bissoondoyal, M.D., 1995. Plantes médicinales de Maurice, tome 1. Editions de l’Océan Indien, Rose-Hill, Mauritius. 495 pp.

Other references

  • Dahal, K.R., Utomo, B.I. & Brink, M., 2003. Agave sisalana Perrine. In: Brink, M. & Escobin, R.P. (Editors). Plant Resources of South-East Asia No 17. Fibre plants. Backhuys Publishers, Leiden, Netherlands. pp. 68–75.
  • Dharmshaktu, N.S., Prabhakaran, P.K. & Menon, P.K., 1987. Laboratory study on the mosquito larvicidal properties of leaf and seed extract of the plant Agave americana. Journal of Tropical Medicine & Hygiene 90(2): 79–82.
  • Gbolade, A.A., Olayemi, J.O., Elujoba, A.A., Sofowora, A. & Adesina, S.K., 1992. Factors affecting the levels of steroidal sapogenins in Nigerian Agave and Furcraea species. Fitoterapia 63(1): 45–48.
  • Lorenza-Salinas, M., Ogura, T. & Soffchi, L., 2001. Irritant contact dermatitis caused by needle-like calcium oxalate crystals, raphides, in Agave tequilana among workers in tequila distilleries and agave plantations. Contact Dermatitis 44(2): 94.
  • McDaniel, R.G., 1985. Field evaluations of Agave in Arizona. Desert Plants 7(2): 57–60.
  • Nel, J.L., Richardson, D.M., Rouget, M., Mgidi, T.N., Mdzeke, N., Le Maitre, D.C., van Wilgen, B.W., Schonegevel, L., Henderson L. & Neser, S., 2004. A proposed classification of invasive alien plant species in South Africa: towards prioritizing species and areas for management action. South African Journal of Science 100: 53–64.
  • Parmar, V.S., Jha, H.N., Gupta, A.K., Prasad, A.K., Gupta, S., Boll, P.M. & Tyagi, O.D., 1992. New antibacterial tetratriacontanol derivatives from Agave americana L. Tetrahedron 48(7): 1281–1284.
  • Sukumaran, D., Parashar, B.D. & Rao, K.M., 1994. Molluscicidal properties of Agave americana and Balanites aegyptica. International Journal of Pharmacognosy 32(3): 232–238.
  • Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.
  • Yang, C.-R., Zhang, Y., Jacob, M.R., Khan, S.I., Zhang, Y.-J. & Li, X.-C., 2006. Antifungal activity of C-27 steroidal saponins. Antimicrobial Agents and Chemotherapy 50(5): 1710–1714.

Author(s)

  • P. Oudhia, SOPAM, 28-A, Geeta Nagar, Raipur, 492001, C.G., India

Correct citation of this article

Oudhia, P., 2007. Agave americana L. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 12 November 2020.