Acmella oleracea

Acmella oleracea is a flowering herb in the plant family Asteraceae, also known as toothache plant or paracress as the leaves and flower heads contain an analgesic agent Spilanthol used to numb toothache. It is native to the tropics of Brazil, and is grown as an ornamental (and occasionally as a medicinal) in various parts of the world. A small, erect plant, it grows quickly and sends up gold and red flower inflorescences. It is frost-sensitive but perennial in warmer climates.

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Synonyms

• Spilanthes oleracea L. (1767)
• Spilanthes acmella auct. non (L.) Murr.

For more information on synonyms, see the Plant Name Database entry on Spilanthes.

Vernacular names

The English common name, toothache plant, is synonymous with the Swedish common name tandvärksplanta; both stem from the analgesic alkylamides the plant contains. The name paracress is in reference to the Northern Brazil state Pará.

It is known in French as brède mafane and cresson de Para, and in Portuguese as agrião do Pará and jambú.^[1]

Culinary uses

For culinary purposes, small amounts of shredded fresh leaves add a unique flavour to salads. Cooked leaves lose their strong flavour and may be used as leafy greens. Both fresh and cooked leaves are used in dishes in parts of Brazil, often combined with chillies and garlic to add flavor and vitamins to other foods. A related species is used in several Southeast Asian dishes. Consumption of portions or whole flowers have been reportedly used to offset the intense heat of chillies and peppers.

Popular uses

A decoction or infusion of the leaves and flowers is recommended for stammering, toothache, stomatitis and throat complaints. Eating a whole flower bud results in an extremely strong tingling sensation accompanied by excessive saliva production.

Properties

The most important taste-active molecules present are the alkamides and especially, (2E,6Z,8E)-deca-2,6,8-trienoic acid N-isobutyl amide or spilanthol,

which is responsible for the trigeminal and saliva-inducing effects of products such as Jambu oleoresin, a concentrated extract from Paracress.^[2]

Extracts using hexane of freshly harvested flowers of S. acmella were bioassayed against A. aegyptii larvae and H. zea (corn earworm) neonates. Mosquitocidal assays on A. aegyptii using spilanthol indicated that they were very active. Spilanthol had a LD₁₀₀ (24 h) at 12.5 mg/mL concentrations and showed 50% mortality at 6.25 mg/mL.

The mixture of isomers of spilanthol showed a 66% weight reduction of H. zea neonate larvae at 250 mg/mL concentration after 6 days.^[2]

Spilanthes acmella has also been shown to have a strong diuretic action in rats.^[3]

The minimum inhibitory concentration of spilanthol against yeasts C. albicans, C. krusei, C. parapsilosis, and C. tropicalis and bacteria Staphylococus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans is larger than 1000 μg/ml and thus largely considered inactive.^[4]

Besides the main active ingredient spilanthol, Acmella also contains stigmasterol and stigmasteryl-3-O-b-D-glucopyranoside together with a mixture of triterpenes, and long chain fatty esters.

The isolation and total synthesis of the active ingredients have been reported.^[5]

References