title: Formation of strecker aldehydes from polyphenol-derived quinones and alpha-amino acids in a nonenzymic model system.
abstract: Fruits and vegetables contain naturally occurring polyphenolic compounds that can undergo enzyme-catalyzed oxidation during food preparation. Many of these compounds contain catechol (1,2-dihydroxybenzene) moieties that may be transformed into o-quinone derivatives by polyphenoloxidases and molecular oxygen. Secondary reactions of the o-quinones include the Strecker degradation of ambient amino acids to form flavor-important volatile aldehydes. The purpose of this work was to investigate the mechanism of the polyphenol/o-quinone/Strecker degradation sequence in a nonenzymic model system. By using ferricyanide ion as the oxidant in pH 7.17 phosphate buffer at 22 degrees C, caffeic acid, chlorogenic acid, (+) catechin, and (-) epicatechin were caused to react with methionine and phenylalanine to produce Strecker aldehydes methional and phenylacetaldehyde in 0.032-0.42% molar yields (0.7-10 ppm in reaction mixtures). Also, by employing l-proline methyl ester in a reaction with 4-methylcatechol, a key reaction intermediate, 4-(2'-carbomethoxy-1'-pyrrolidinyl)-5-methyl-1,2-benzoquinone (7), was isolated and tentatively identified.
authors.affiliation: Procter & Gamble Company, Winton Hill Business Center, 6300 Center Hill Road, Cincinnati, Ohio 45224, USA. georgerizzi@prodigy.net
authors.forename: George P
authors.initials: GP
authors.lastname: Rizzi
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry*; D002392:Catechin / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005292:Ferricyanides / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D016877:Oxidants / Q000737:chemistry; D010636:Phenols / Q000737:chemistry*; D059808:Polyphenols; D011809:Quinones / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D000596:Amino Acids; D005292:Ferricyanides; D005419:Flavonoids; D016877:Oxidants; D010636:Phenols; D059808:Polyphenols; D011809:Quinones; C007931:hexacyanoferrate III; D002392:Catechin