Allyl isothiocyanate is the organosulfur compound with the formula CH2CHCH2NCS. This colourless oil is responsible for the pungent taste of mustard, horseradish, and wasabi. It is slightly soluble in water, but well soluble in most organic solvents.
Biosynthesis and biological functions
Allyl isothiocyanate comes from the seeds of black mustard (Brassica nigra
) 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.
Allyl isothiocyanate 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.
Commericial and other applications
Allyl isothiocyanate is produced commercially by the reaction of allyl chloride
and potassium thiocyanate
- CH2=CHCH2Cl + KSCN → CH2=CHCH2NCS + KCl
The product obtained in this fashion is sometimes known as synthetic mustard oil.
Allyl isothiocyanate can also be liberated by drydistillation
of the seeds. The product obtained in this fashion is known as volatile oil of mustard
and is usually around 92% pure. It is used principally as a flavoring
agent in foods. Synthetic allyl isothiocyanate is used as an insecticide
, and nematocide, and is used in certain cases for crop protection.
Hydrolysis of allyl isothiocyanate gives allyl amine.
Allyl isothiocyanate is mildly toxic with ld50
of 151 mg/kg but is a dangerous lachrymator