Sinigrin

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Sinigrin is a natural compound found in many mustard-family plants, including Brussels sprouts, broccoli, and especially black mustard seeds. It belongs to a group of chemicals called glucosinolates that plants use for defense. When plant tissue is crushed or damaged, an enzyme called myrosinase breaks sinigrin apart, releasing a compound that quickly rearranges into allyl isothiocyanate—the spicy, pungent taste you get from mustard and horseradish.

White mustard seeds contain a related compound called sinalbin, which is less pungent than sinigrin-based mustard oil.

History and structure: Sinigrin was first identified in 1839 from black mustard. Chemists later confirmed that natural glucosinolates like sinigrin have a specific Z (syn) form around a C=N bond. Sinigrin is made in plants from the amino acid methionine through several steps.

Role in plants: The main purpose of glucosinolates like sinigrin is plant defense. When the plant is damaged, the mustard oil bomb (allyl isothiocyanate) is produced, which is toxic to many insect predators and helps protect the plant.

In foods: At typical dietary levels, sinigrin itself isn’t toxic to humans and can add to flavor. It’s also a precursor to other volatile compounds such as epithionitrile, allyl cyanide, and allyl thiocyanate.