Sinalbin

Sinalbin is a glucosinolate primarily found in white mustard seeds (Sinapis alba) and in some other Brassicaceae. It is also known as p-hydroxybenzyl glucosinolate or 4-hydroxybenzyl glucosinolate. The molecule consists of a glucose residue linked to a sulfur-containing core, with a 4-hydroxybenzyl (p-hydroxyphenylmethane) side chain derived from the amino acid tyrosine.

When plant tissue is damaged, sinalbin is hydrolyzed by the enzyme myrosinase to yield glucose and a reactive aglycone that rearranges to the corresponding isothiocyanate, p-hydroxybenzyl isothiocyanate. This volatile isothiocyanate is largely responsible for the characteristic pungent aroma and flavor of mustard. Depending on conditions and proteins present, alternative breakdown products such as nitriles can also form.

Occurrence and function: Sinalbin is a major glucosinolate in white mustard seeds and contributes to the peppery, sharp flavor of mustard condiments. Like other glucosinolates, it serves as a chemical defense for the plant against herbivores and pathogens. Its levels vary with plant variety, tissue type, developmental stage, and processing.

Biosynthesis: Sinalbin is produced via the plant's glucosinolate biosynthetic pathway, beginning with the amino acid tyrosine and proceeding through core glucosinolate formation, sulfation, and glycosylation steps that culminate in the intact sinalbin molecule.

Safety and applications: At typical dietary levels, sinalbin and its breakdown products are not considered highly toxic, though isothiocyanates can irritate mucous membranes. In foods, sinalbin contributes to mustard flavor and aroma; in research, it serves as a marker for white mustard composition and glucosinolate studies.