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Acmella oleracea (syn. Spilanthes oleracea, S. acmella) is a species of flowering herb in the family Asteraceae. Common names include toothache plant and paracress. In Brazil it is called jambu. Its native distribution is unclear, but it is likely derived from a Brazilian Acmella species. It is grown as an ornamental and it is used as a medicinal remedy in various parts of the world. A small, erect plant, it grows quickly and bears gold and red inflorescences. It is frost-sensitive but perennial in warmer climates.
For culinary purposes, small amounts of shredded fresh leaves are said to 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 such as stews in northern Brazil, especially in the state of Pará. They are combined with chilis and garlic to add flavor and vitamins to other foods.
The flower bud has a grassy taste followed by a strong tingling or numbing sensation and often excessive salivation, with a cooling sensation in the throat. The buds are known as "buzz buttons", "Szechuan buttons", "sansho buttons", and "electric buttons". In India, they are used as flavoring in chewing tobacco.
A concentrated extract of the Spilanthes plant identified as Jambu is used as a flavoring agent in many countries worldwide. EFSA and JECFA reviewed a feeding study in rats conducted by Moore et al and both authorities recognized that the no adverse effect level for spilanthol was 572 mg/kg b.w./day, yielding a safe dose of spilanthol of 1.9 mg/kg b.w./day, or 133.5 mg/70-kg male/day, 111 mg/58-kg female/day, or 38 mg/20-kg child/day.
The use of jambu extract as a food flavor is described as having an odor of citrus, herbal, tropical or musty odor, and its taste can be pungent, cooling, tingling, numbing, or effervescent. Thus, as described, the flavor use of jambu extract includes the ability induce a mouth-watering sensation in the oral cavity and the ability to promote the production of saliva. Spilanthol, the major constituent of jambu extract, is responsible for the perception of a mouth-watering flavor sensation, as well as the ability to promote salivation as a sialogogue, perhaps through its astringent action or its pungent taste in the oral cavity.
This plant prefers well-drained, black (high organic content) soil. If starting outdoors, the seeds should not be exposed to cold weather, so start after last frost. Seeds need direct sunlight to germinate, so don't bury them.  
As a bush plant used for treating toothache, the analgesic effect of the Spilanthes plant has been attributed to the presence of constituents containing an N-isobutylamide moiety, such as spilanthol, a substance that has been found to be an effective sialogogue, an agent that promotes salivation. Spilanthol is absorbed trans-dermally and through the buccal mucosa. Spilanthol may activate TRPA1, a specific transient receptor potential (TRP) ion channel in the oral cavity. In addition to capsaicin, allyl isothiocyanate, and cinnamaldehyde, spilanthol is also reported to affect the catecholamine nerve pathways present in the oral cavity that promote the production of saliva, which is responsible for its ability to induce a mouth-watering sensation when used as a flavor (and associated with the tingling or pungent flavoring sensation in some individuals).
|Pharmacological activity||Species||Part used||Type of extract||Models used|
|Antimalarial, larvicidal||S. acmella Murr.||Flowers||Ethanol||Anopheles, Aedes, Culex larvae|
|Antinociception, antihyperalgesic||S. acmella||Flowers||CWE||Formalin test of nociception and carrageenan-induced thermal hyperalgesia in rats|
|Antinociception, antihyperalgesic||Acmella uliginosa, (Sw.) Cass||Flowers||Methanol||Chemicals (acetic acid-induced abdominal constriction and formalin-, capsaicin-, glutamate-induced paw-licking test) and thermal models (hot-plate test) of nociception in mice|
|Immunomodulatory||S. acmella Murr.||Leaves||Ethanol||Macrophage function in mice|
|Immunomodulatory||S. acmella||Leaves||Ethanol||Neutrophil adhesion test in rat|
|Insecticidal||S. calva||Leaves and flowers||Petroleum ether, ethyl acetate and methanol||Helopeltis theivora|
|Antimalarial, larvicidal||S. acmella, S. calva, S. paniculata||Flowers||Hexane||A. stephensi, A. culicifacies, C. quinquefasciatus larvae|
|Antioxidant||S. acmella||Leaves, stems||Methanol||DPPH, SOD assay|
|Antihepatoxic||S. ciliata||Whole plant||Ethanol||Paracetamol-induced hepatic damage in rats|
|Antimicrobial||S. calva||Roots||Methanol||Oral microflora: Streptococcus mutans, Lactobacillus acidophilus and Candida albicans|
|Anti-inflammatory||S. acmella||Aerial parts||Ethanol||Lipopolysaccharide-activated murine macrophage model|
|Antimalarial, larvicidal||S. mauritiana||Aerial parts||Methanol extract||Aedes aegypti larvae|
|Insecticidal||S. acmella Murr.||Leaves and flowers||Aqueous||Chilo partellus|
|Diuretic||S. acmella||Flowers||CWE||Hydrated rats|
|Antioxidant||S. acmella Murr.||Aerial parts||Chloroform, hexane, ethyl actate, methanol||2,2-Diphenyl-1-picrylhydrazyl (DPPH) and superoxide dismutase (SOD) assay|
|Antimicrobial||S. americana||Whole plant||Aqueous, ethanol and hexane||Staphylococcus aureus, Streptococcus hemolytic, Bacillus cereus, Pseudomonas aeruginosa and Escherichia coli|
|Antipyretic||S. acmella Murr.||NA||Aqueous||Aspirin-treated rats|
|Diuretic||S. acmella||Leaves||Petroleum ether, chloroform and ethanol||Hydrated Wistar albino rats|
|Antimicrobial||S. paniculata||Leaves||NA||Bacillus subtilis, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa,Candida
albicans and Microsporum gypseum
|Antimicrobial||S. mauritiana||Roots and flowers||NA||Staphylococcus, Enterococcus, Pseudomonas, Escherichia and Klebsiella, Salmonella|
|Antimicrobial||S. mauritiana||Roots and flowers||NA||Candida species and Aspergillus species|
|Antimicrobial||S. acmella Linn.||Flower heads||Petroleum ether||Fusarium oxysporium, F. moniliformis, Aspergillus niger and A. paraciticus|
|Local anaesthetic||S. acmella Murr.||NA||Aqueous||Xylocaine-induced guinea pig and frog|
|Antimalarial, larvicidal||S. mauritiana||Leaves||Crude powder||A. gambiae, Culex larvae|
|Anti-inflammatory||S. acmella||Aerial parts||Aqueous||Carragenan-induced paw edema in rats|
|Aphrodisiac||S. acmella L. Murr.||Flowers||Ethanol||Nitric oxide release in human corpus cavernosum cell line and penile erection in rats|
|Insecticidal||S. acmella||NA||NA||Periplaneta Americana|
|HIV-1 protease inhibitor||S. acmella L.||Whole plant||Chloroform, methanol and water||In vitro HIV-1 protease solution assay method|
|Analgesic||S. acmella||Aerial parts||Aqueous||Acetic acid-induced writhing response in albino mice|
|Pancreatic lipase-inhibitory||S. acmella||Flowers||Ethanol||In vitro test|
|Vasorelaxant||S. acmella Murr.||Aerial parts||Chloroform, hexane, ethyl acetate, methanol||Phnenylephrine-induced rat|
|Antimutagenic||S. calva||NA||Chloroform||Ames Salmonella/microsome assay|
|Convulsant||S. acmella||Whole plant||Hexane||Electroencephalo-graph behaviour of rats|
The most important taste-active molecules present are fatty acid amides such as spilanthol, which is responsible for the trigeminal and saliva-inducing effects of products such as jambú oleoresin, a concentrated extract of the plant. It also contains stigmasteryl-3-O-b-D-glucopyranoside and a number of triterpenes. The isolation and total synthesis of the active ingredients have been reported.
Biological pest control
Extracts were bioassayed against yellow fever mosquito (Aedes aegypti) and corn earworm moth (Helicoverpa zea) larvae. The spilanthol proved effective at killing mosquitoes, with a 24-hour LD100 of 12.5 µg/mL, and 50% mortality at 6.25 µg/mL. The mixture of spilanthol isomers produced a 66% weight reduction of corn earworm larvae at 250 µg/mL after 6 days.
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