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Acmella oleracea (L.) R.K.Jansen

Protologue
Syst. Bot. Monogr. 8: 65 (1985).
Family
Asteraceae (Compositae)
Chromosome number
2n = 60, 78
Synonyms
Spilanthes oleracea L. (1767), Spilanthes acmella auct. non (L.) Murr.
Vernacular names
Toothache plant, para-cress (En). Brède mafane, cresson de Para (Fr). Agrião do Pará, jambú (Po).
Origin and geographic distribution
Acmella oleracea is not known from the wild. It is thought to have been derived through cultivation from Acmella alba (L’Hér.) R.K.Jansen, a species native to Peru and Brazil. It must have been in cultivation for a considerable time and has spread throughout the tropics. It is locally cultivated throughout Africa and escapes from cultivation have been reported. In East Africa it has become naturalized. It was probably introduced in the Indian Ocean Islands by the Portuguese and subsequently spread in East Africa by Indian labourers who came to work on railroad construction around 1900.
Uses
In the Indian Ocean islands (Comoros, Madagascar, Réunion, Mauritius) and India the main use of the leaves of Acmella oleracea is as a steamed vegetable. The raw leaves are used as a flavouring for salads, soups and meats in Brazil and India. It is grown widely as an ornamental because of the attractive colourful heads.
The most common and widespread medicinal use is to treat toothache and throat and gum infections. Worldwide the flower heads are used either fresh or dried and powdered, but the use of roots and leaves has been recommended as well. The plant is further recommended as a cure for dysentery and rheumatism, and to enhance the immune system. It is used against blood parasites, especially against malaria, both prophylactic and curative.
Properties
Data on nutritional composition are not available. Raw Acmella leaves and flower heads have a pungent taste; they cause numbing of the mouth when chewed and induce the production of saliva. This sensation may be attributed to the alkylamide fraction.
The flower heads contain up to 1.25% of spilanthol (N-isobutyl-4,6-decadienamide), an antiseptic alkaloid. Spilanthol is effective at very low concentrations against blood parasites. It is a poison for most invertebrates, but is said to be harmless to warm-blooded animals. Different sources commenting on the composition of the essential oil distilled from fresh flowers agree on a high content of β-caryophyllene (21–30%). Other major constituents reported are limonene, thymol, γ-cadinene and germacrene.
In-vitro studies have shown strong antibacterial activity against Escherichia, Klebsiella, Proteus, Pseudomonas, Salmonella and Staphylococcus. Also Candida albicans is inhibited. Use as an insecticide has proved effective against e.g. Aedes, Anopheles and Culex mosquitoes and corn earworm (Helicoverpa zea).
Botany
Annual herb with erect stems, sometimes decumbent. Leaves opposite, simple; petiole 2–6.5 cm long; blade broadly ovate to deltate, 5–11 cm × 4–8 cm, base truncate to shortly attenuate, apex acute to shortly acuminate, margin dentate. Inflorescence a discoid head up to 2.5 cm × 1.5 cm; involucral bracts 15–18, 3-seriate, up to 8 mm × 1 mm, apex acute; receptacular bracts straw-coloured, often tinged purple-red, up to 6 mm × 1 mm. Disk flowers 400–620, corolla 5-merous, yellow, up to 3.5 mm long. Fruit an achene 2–2.5 mm × 1 mm; pappus consisting of 2 bristles.
Acmella is a pantropical genus of about 30 species, with 2 of these native to tropical Africa, and 2 introduced. Most Acmella species were formerly considered to belong to the genus Spilanthes. The 2 native species, Acmella caulirhiza Delile (synonym: Spilanthes mauritianus auct. non (Rich.) DC.) and Acmella uliginosa (Sw.) Cass., have similar uses as Acmella oleracea and have undoubtedly been mixed up in the literature. Acmella caulirhiza can be distinguished from Acmella oleracea by the presence of ray flowers. Acmella uliginosa has a 4-merous corolla.
Ecology
As an escape from cultivation Acmella oleracea is found in weedy habitats. Naturalized populations are usually found in wet localities such as lakeside marshes.
Management
Acmella oleracea is grown as a vegetable in Madagascar and Comoros, and also in Réunion and Mauritius, but details have not been reported. It is sold in markets in Madagascar throughout the year with peak supplies from November–March. As an ornamental it is propagated by seed or by cuttings taken from plants in the vegetative phase. For germination a temperature of at least 21°C is needed. It needs frequent watering.
Genetic resources and breeding
As Acmella oleracea is widely grown, and is naturalized in parts of East Africa, it is certainly not threatened.
Prospects
It would be worthwhile documenting the cultivation practices, characteristics and properties of Acmella oleracea grown in the Indian Ocean islands. Acmella oleracea and its wild ancestor Acmella alba are interesting for further research on medicinal potential, especially concerning activity against blood parasites other than malaria. The research community should be made aware of the updated nomenclature in the genera Acmella and Spilanthes to avoid replication of research findings, doubtful identifications and the use of incorrect names.
Major references
• Hind, N. & Biggs, N., 2003. Acmella oleracea: Compositae. Curtis’s Botanical Magazine 20(1): 31–39.
• Jansen, R.K., 1985. The systematics of Acmella (Asteraceae-Heliantheae). Systematic Botany Monographs 8. 115 pp.
• Ramsewak, R.S., Erickson, A.J. & Nair, M.G., 1999. Bioactive N-isobutylamides from the flower buds of Spilanthes acmella. Phytochemistry 51(6): 729–732.
Other references
• Cech, R.A., 1996. Spilanthes. [Internet] http://www.b-and-t-world-seeds.com/Horizon.htm. Accessed November 2003.
• Fabry, W., Okemo, P.O. & Ansorg, R., 1998. Antibacterial activity of East African medicinal plants. Journal of Ethnopharmacology 60(1): 79–84.
• Gasquet, M., Delmas, F., Timon-David, P., Keita, A., Guindo,M., Koita, N., Diallo, D. & Doumbo, O., 1993. Evaluation in vitro and in vivo of a traditional antimalarial, "Malarial 5". Fitoterapia 64(5): 423–426.
• Hind, D.J.N., Jeffrey, C. & Scott, A.J., 1993. Composées. In: Bosser, J., Guého, J. & Jeffrey, C. (Editors). Flore des Mascareignes. Famille 109. The Sugar Industry Research Institute, Mauritius, l’Institut Français de Recherche Scientifique pour le Développement en Coopération (ORSTOM), Paris, France & Royal Botanic Gardens, Kew, Richmond, United Kingdom. 261 pp.
• Jansen, R.K., 1981. Systematics of Spilanthes (Compositae: Heliantheae). Systematic Botany 6(3): 231–257.
• Roemantyo, 1993. Spilanthes Jacquin. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 264–266.
Author(s)
C.H. Bosch
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
G.J.H. Grubben
Boeckweijdt Consult, Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate editors
C.-M. Messiaen
Bat. B 3, Résidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Photo editor
E. Boer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Bosch, C.H., 2004. Acmella oleracea (L.) R.K.Jansen. [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>. Accessed .
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