title: Modifications of tryptophan oxidation by phenolic-rich plant materials.
abstract: The role of plant phenolics as possible antioxidants was studied toward oxidation of tryptophan. Sources of plant phenolics included byproducts of deoiling processes, such as camelina, rapeseed, and soy meals and Scots pine bark drink, as well as berry phenolics from raspberry, black currant, and rowanberry. The oxidation of tryptophan and its individual oxidation products with and without added phenolics were analyzed by using a validated high-performance liquid chromatography method with diode array and fluorescence detection. Tryptophan in the presence of hexanal and iron (FeCl(2)) was degraded by 77% after 6 days of oxidation, resulting in oxidation products, such as 3a-hydroxypyrroloindole-2-carboxylic acid B, dioxindolylalanine, 5-hydroxy-tryptophan, kynurenine, N-formylkynurenine, and beta-oxindolylalanine. The tryptophan modifications formed upon hexanal and iron treatment were efficiently inhibited by camelina meal followed by rapeseed meal and soy meal. In contrast, phenolics from raspberry, black currant, and rowanberry acted as weak pro-oxidants.
authors.affiliation: Department of Applied Chemistry and Microbiology, University of Helsinki, Finland. hanna.salminen@helsinki.fi
authors.forename: Hanna
authors.initials: H
authors.lastname: Salminen
authors.forename: Helena
authors.initials: H
authors.lastname: Jaakkola
authors.forename: Marina
authors.initials: M
authors.lastname: Heinonen
mesh_terms: D000975:Antioxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D010944:Plants / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D010636:Phenols; D010936:Plant Extracts; D014364:Tryptophan