title: Strecker-type degradation of phenylalanine by methyl 9,10-epoxy-13-oxo-11-octadecenoate and methyl 12,13-epoxy-9-oxo-11-octadecenoate.
abstract: The reaction of methyl 9,10-epoxy-13-oxo-11(E)-octadecenoate, methyl 12,13-epoxy-9-oxo-11(E)-octadecenoate, 4,5(E)-epoxy-2(E)-heptenal, and 4,5(E)-epoxy-2(E)-decenal with phenylalanine in acetonitrile-water (2:1, 1:1, and 1:2) at 80 degrees C and at different pHs and carbonyl compound/amino acid ratios was investigated both to determine if epoxyoxoene fatty esters were able to produce the Strecker-type degradation of the amino acid and to study the relative ability of oxidized long-chain fatty esters and short chain aldehydes with identical functional systems to degrade amino acids. The studied epoxyoxoene fatty esters degraded phenylalanine to phenylacetaldehyde. The mechanism of the reaction was analogous to that described for epoxyalkenals and is suggested to be produced through the corresponding imine, which is then decarboxylated and hydrolyzed. This reaction also produced a conjugated hydroxylamine, which was the origin of the long-chain pyridine-containing fatty ester isolated in the reaction and characterized as methyl 8-(6-pentylpyridin-2-yl)octanoate. Epoxyoxoene fatty esters and epoxyalkenals exhibited a similar reactivity for producing phenylacetaldehyde, therefore suggesting that nonvolatile lipid oxidation products, which are produced to a greater extent than volatile products, should be considered for determining the overall contribution of lipids to Strecker degradation of amino acids produced during nonenzymatic browning. In addition, the obtained data confirm that, analogously to carbohydrates, lipid oxidation products are also able to produce the Strecker degradation of amino acids.
authors.affiliation: Instituto de la Grasa, Consejo Superior de Investigaciones Científicas, Avenida Padre García Tejero 4, 41012 Seville, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Zamora
authors.forename: Emerenciana
authors.initials: E
authors.lastname: Gallardo
authors.forename: José L
authors.initials: JL
authors.lastname: Navarro
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Hidalgo
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives* / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry; D004852:Epoxy Compounds / Q000737:chemistry*; D005227:Fatty Acids / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006863:Hydrogen-Ion Concentration; D015227:Lipid Peroxidation; D009682:Magnetic Resonance Spectroscopy; D015416:Maillard Reaction; D010649:Phenylalanine / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D004852:Epoxy Compounds; D005227:Fatty Acids; C501719:methyl 12,13-epoxy-9-oxo-11-octadecenoate; C501720:methyl 9,10-epoxy-13-oxo-11-octadecenoate; D010649:Phenylalanine; D000079:Acetaldehyde; C013192:phenylacetaldehyde