Allyl isothiocyanate explained

Allyl isothiocyanate (AITC) is a naturally occurring unsaturated isothiocyanate. The colorless oil is responsible for the pungent taste of cruciferous vegetables such as mustard, radish, horseradish, and wasabi. This pungency and the lachrymatory effect of AITC are mediated through the TRPA1 and TRPV1 ion channels.^{[1] [2] [3]} It is slightly soluble in water, but more soluble in most organic solvents.

Biosynthesis and biological functions

Allyl isothiocyanate can be obtained from the seeds of black mustard (Rhamphospermum nigrum) or brown Indian mustard (Brassica juncea). When these mustard seeds are broken, the enzyme myrosinase is released and acts on a glucosinolate known as sinigrin to give allyl isothiocyanate.^[4] This serves the plant as a defense against herbivores; since it is harmful to the plant itself, it is stored in the harmless form of the glucosinolate, separate from the myrosinase enzyme. When an animal chews the plant, the allyl isothiocyanate is released, repelling the animal. Human appreciation of the pungency is learned.^[5]

The compound has been shown to strongly repel fire ants (Solenopsis invicta).^[6] AITC vapor is also used as an antimicrobial and shelf life extender in food packaging.^[5]

Production and applications

Allyl isothiocyanate is produced commercially by the reaction of allyl chloride and potassium thiocyanate:

CH₂=CHCH₂Cl + KSCN → CH₂=CHCH₂NCS + KClThe product obtained in this fashion is sometimes known as synthetic mustard oil. Allyl thiocyanate isomerizes to the isothiocyanate:^[7]

Allyl isothiocyanate can also be liberated by dry distillation of the seeds. The product obtained in this fashion is known as volatile oil of mustard.

It is used principally as a flavoring agent in foods. Synthetic allyl isothiocyanate is used as an insecticide, as an anti-mold agent ^[8] bacteriocide,^[9] and nematicide, and is used in certain cases for crop protection. It is also used in fire alarms for the deaf.^[10]

Hydrolysis of allyl isothiocyanate gives allylamine.

Safety

Allyl isothiocyanate has an LD₅₀ of 151 mg/kg and is a lachrymator (similar to tear gas or mace).

Oncology

Based on in vitro experiments and animal models, allyl isothiocyanate exhibits many of the desirable attributes of a cancer chemopreventive agent.^[11]

See also

• Mustard plaster, traditional home remedy
• Piperine, the piquant chemical in black pepper
• Capsaicin, the piquant chemical in chili peppers
• Allicin, the piquant flavor chemical in raw garlic

Notes and References

1. Everaerts . W. . Gees . M. . Alpizar . Y. A. . Farre . R. . Leten . C. . Apetrei . A. . Dewachter . I. . van Leuven . F. . Vennekens . R.. The Capsaicin Receptor TRPV1 is a Crucial Mediator of the Noxious Effects of Mustard Oil . Current Biology . 2011 . 21 . 4 . 316–321 . 21315593 . 10.1016/j.cub.2011.01.031 . 13151479 . free. 2011CBio...21..316E .
2. Brône, B. . Peeters, P. J. . Marrannes, R. . Mercken, M. . Nuydens, R. . Meert, T. . Gijsen, H. J. . Tear gasses CN, CR, and CS are potent activators of the human TRPA1 receptor . . 2008 . 231 . 2 . 150–156 . 18501939 . 10.1016/j.taap.2008.04.005 .
3. Ryckmans, T. . Aubdool, A. A. . Bodkin, J. V. . Cox, P. . Brain, S. D. . Dupont, T. . Fairman, E. . Hashizume, Y. . Ishii, N. . Design and Pharmacological Evaluation of PF-4840154, a Non-Electrophilic Reference Agonist of the TrpA1 Channel . Bioorganic & Medicinal Chemistry Letters . 2011 . 21 . 16 . 4857–4859 . 21741838 . 10.1016/j.bmcl.2011.06.035 . etal.
4. 10.1016/j.phytochem.2019.112100 . free . Glucosinolate structural diversity, identification, chemical synthesis and metabolism in plants . 2020 . Blažević . Ivica . Montaut . Sabine . Burčul . Franko . Olsen . Carl Erik . Burow . Meike . Rollin . Patrick . Agerbirk . Niels . Phytochemistry . 169 . 112100 . 31771793 . 2020PChem.169k2100B . 208318505 .
5. Book: Melton . Laurence . The Encyclopedia of Food Chemistry . Elsevier . 2019 . 978-0-12-814045-1 . Netherlands .
6. 10.1007/s13355-019-00613-5 . Wasabi versus red imported fire ants: Preliminary test of repellency of microencapsulated allyl isothiocyanate against Solenopsis invicta (Hymenoptera: Formicidae) using bait traps in Taiwan . 2019 . Hashimoto . Yoshiaki . Yoshimura . Masashi . Huang . Rong-Nan . Applied Entomology and Zoology . 54 . 2 . 193–196 . 2019AppEZ..54..193H .
7. 10.1021/ed048p81 . The Preparation and Isomerization of Allyl Thiocyanate. An Organic Chemistry Experiment . 1971 . Emergon . David W. . Journal of Chemical Education . 48 . 1 . 81 . 1971JChEd..48...81E .
8. US Patent No. 8691042
9. Masuda . Shuichi . Masuda . Hideki . Shimamura . Yuko . Sugiyama . Chitose . Takabayashi . Fumiyo . Improvement Effects of Wasabi (Wasabia japonica) Leaves and Allyl Isothiocyanate on Stomach Lesions of Mongolian Gerbils Infected with Helicobacter pylori . Natural Product Communications . April 2017 . 12 . 4 . 595–598 . 10.1177/1934578X1701200431 . 30520603. 54567566 . free .
10. Web site: Phillipson . Tacye . Why would you want a wasabai fire alarm? . National Museums Scotland Blog . 29 August 2018 . 10 March 2022.
11. 19960458. 2010. Zhang. Y. Allyl isothiocyanate as a cancer chemopreventive phytochemical. Molecular Nutrition & Food Research. 54. 1. 127–35. 10.1002/mnfr.200900323. 2814364.