Glucosinolate

Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged. These natural chemicals most likely contribute to plant defence against pests and diseases, and impart a characteristic bitter flavor property of cruciferous vegetables. Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged. These natural chemicals most likely contribute to plant defence against pests and diseases, and impart a characteristic bitter flavor property of cruciferous vegetables. Glucosinolates occur as secondary metabolites of almost all plants of the order Brassicales. Ordered in the Brassicales are for example the economically important family Brassicaceae as well as Capparaceae and Caricaceae.Outside of the Brassicales, the genera Drypetes and Putranjiva in the family Putranjivaceae are the only other known occurrence of glucosinolates.Glucosinolates occur in various edible plants such as cabbage (white cabbage, Chinese cabbage, broccoli) watercress, horseradish, capers and radishes where the breakdown products often contribute a significant part of the distinctive taste. The glucosinolates are also found in seeds of these plants. Glucosinolates constitute a natural class of organic compounds that contain sulfur and nitrogen and are derived from glucose and an amino acid. They are water-soluble anions and belong to the glucosides. Every glucosinolate contains a central carbon atom, which is bound via a sulfur atom to the thioglucose group and via a nitrogen atom to a sulfate group (making a sulfated aldoxime). In addition, the central carbon is bound to a side group; different glucosinolates have different side groups, and it is variation in the side group that is responsible for the variation in the biological activities of these plant compounds.The semisystematic naming of glucosinolates consists of the chemical name of that side chain followed by 'glucosinolate'. Spelling glucosinolate names in one or two words (e.g. allylglucosinolate versus allyl glucosinolate) are both in use and has equivalent meaning. Isothiocyanates must be spelled in two words. The essence of glucosinolate chemistry is the ability of a glucosinolate to convert into an isothiocyanate (a 'mustard oil') upon hydrolysis of the thioglucoside bond by the enzyme myrosinase. Some glucosinolates: About 132 different glucosinolates are known to occur naturally in plants. They are synthesized from certain amino acids: So-called aliphatic glucosinolates derived from mainly methionine, but also alanine, leucine, isoleucine, or valine. (Most glucosinolates are actually derived from chain-elongated homologues of these amino acids, e.g. glucoraphanin is derived from dihomomethionine, which is methionine chain-elongated twice). Aromatic glucosinolates include indolic glucosinolates, such as glucobrassicin, derived from tryptophan and others from phenylalanine, its chain-elongated homologue homophenylalanine, and sinalbin derived from tyrosine. The plants contain the enzyme myrosinase, which, in the presence of water, cleaves off the glucose group from a glucosinolate. The remaining molecule then quickly converts to an isothiocyanate, a nitrile, or a thiocyanate; these are the active substances that serve as defense for the plant. Glucosinolates are also called mustard oil glycosides. The standard product of the reaction is the isothiocyanate (mustard oil); the other two products mainly occur in the presence of specialised plant proteins that alter the outcome of the reaction.