Sinigrin

Occurrence

The compound was first reported in 1839, after its isolation from black mustard Brassica nigra, also known as Sinapis nigra, after which it was named. Sinigrin is now known to occur widely in other brassica families including Brassicaceae and Capparaceae.

Structure

The chemical structure of sinigrin had been established by 1930. This showed that it is a glucose derivative with β-D-glucopyranose configuration. It was unclear whether the C=N bond was in the Z (or syn) form, with sulfur and oxygen substituents on the same side of the double bond, or the alternative E form in which they are on opposite sides. The matter was settled by X-ray crystallography of its potassium salt in 1963. It is now known that all natural glucosinolates are of Z form.

Synthesis

Biosynthesis

Sinigrin is biosynthesised from the amino acid methionine in a multi-step pathway.

Laboratory synthesis

The first laboratory syntheses of sinigrin was published in 1965.

Function

Main article: Glucosinolate

The natural role of glucosinolates are as plant defense compounds. The enzyme myrosinase removes the glucose group in sinigrin to give an intermediate which spontaneously rearranges to allyl isothiocyanate, the compound responsible for the pungent taste of Dijon mustard. This is a reactive material which is toxic to many insect predators and its production is triggered when the plant is damaged. This effect has been called the mustard oil bomb. Singrin is also known to be allelopathic. At concentrations typically found in foods, the glucosinolates are not toxic to humans and can be useful flavor components.

Sinigrin is unusual among the glucosinolates because it is also known to be the natural precursor for other volatile compounds including epithionitrile, allyl cyanide and allyl thiocyanate.

References

References

1. Richard, H.. "Arômes alimentaires".
2. (1965). "The synthesis of sinigrin". Chemical Communications.
3. (2020). "Glucosinolate structural diversity, identification, chemical synthesis and metabolism in plants". Phytochemistry.
4. (2001). "The chemical diversity and distribution of glucosinolates and isothiocyanates among plants". Phytochemistry.
5. (1963). "Crystal Structure of Sinigrin". Nature.
6. (1970). "Refinement of the crystal structure of sinigrin". Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry.
7. (1996). "Practical Synthesis of Sinigrin". Journal of Carbohydrate Chemistry.
8. (2008). "β-Glucosidases as detonators of plant chemical defense". Phytochemistry.
9. (1980). ""Die Senfolbombe": Zur Kompartimentierung des Myrosinasesystems". Biochemie und Physiologie der Pflanzen.
10. (2008). "A Chemical Trait Creates a Genetic Trade-Off Between Intra- and Interspecific Competitive Ability". Ecology.
11. (1983). "Glucosinolates and their breakdown products in food and food plants". C R C Critical Reviews in Food Science and Nutrition.