title: 2-(1H-pyrrolyl)carboxylic acids as pigment precursors in garlic greening.
abstract: Six model compounds having a 2-(1 H-pyrrolyl)carboxylic acid moiety and a hydrophobic R group were synthesized to study their effects on garlic greening, the structures of which are similar to that of 2-(3,4-dimethyl-1 H-pyrrolyl)-3-methylbutanoic acid (PP-Val) (a possible pigment precursor for garlic greening). The puree of freshly harvested garlic bulbs turned green after being soaked in solutions of all these compounds, and with both increasing concentrations and incubation time the green color of the puree became deeper. In contrast, neither pyrrole alone nor pyrrole combined with free amino acids had the ability to discolor the puree. The compounds exhibited a good relationship between structure and activity of garlic greening, namely, the smaller the size of the R group, the larger the contribution. Also, it was found that the unidentified yellow species can be produced by reacting the model compounds with pyruvic acid at room temperature (23-25 degrees C). Moreover, blue species were formed by incubation of the model compounds with di(2-propenyl) thiosulfinate at room temperature. On the basis of these observations, a pathway for garlic greening was proposed.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.forename: Husile
authors.initials: H
authors.lastname: Nanding
authors.forename: Na
authors.initials: N
authors.lastname: Han
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.forename: Guanghua
authors.initials: G
authors.lastname: Zhao
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005511:Food Handling; D005737:Garlic / Q000737:chemistry*; D010860:Pigments, Biological / Q000032:analysis* / Q000096:biosynthesis; D019289:Pyruvic Acid / Q000378:metabolism; D013441:Sulfinic Acids / Q000378:metabolism; D013454:Sulfoxides / Q000378:metabolism
chemical_list: D002264:Carboxylic Acids; D010860:Pigments, Biological; D013441:Sulfinic Acids; D013454:Sulfoxides; C100040:thiosulfinic acids; D019289:Pyruvic Acid