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      Ammoxidation of Lignocellulosic Materials: Formation of Nonheterocyclic Nitrogenous Compounds from Monosaccharides

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          Abstract

          Ammoxidized technical lignins are valuable soil-improving materials that share many similarities with native terrestrial humic substances. In contrast to lignins, the chemical fate of carbohydrates as typical minor constituents of technical lignins during the ammoxidation processes has not been thoroughly investigated. Recently, we reported the formation of N-heterocyclic, ecotoxic compounds (OECD test 201) from both monosaccharides ( d-glucose, d-xylose) and polysaccharides (cellulose, xylan) under ammoxidation conditions and showed that monosaccharides are a source more critical than polysaccharides in this respect. GC/MS-derivatization analysis of the crude product mixtures revealed that ammoxidation of carbohydrates which resembles the conditions encountered in nonenzymatical browning of foodstuff affords also a multitude of nonheterocyclic nitrogenous compounds such as aminosugars, glycosylamines, ammonium salts of aldonic, deoxyaldonic, oxalic and carbaminic acids, urea, acetamide, α-hydroxyamides, and even minor amounts of α-amino acids. d-Glucose and d-xylose afforded largely similar product patterns which differed from each other only for those products that were formed under preservation of the chain integrity and stereoconfiguration of the respective monosaccharide. The kinetics and reaction pathways involved in the formation of the different classes of nitrogenous compounds under ammoxidation conditions are discussed.

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          Most cited references13

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          Formation of aroma-active strecker-aldehydes by a direct oxidative degradation of Amadori compounds.

          alpha-Dicarbonyls, generated by sugar degradation, catalyze the formation of the so-called Strecker aldehydes from alpha-amino acids. To check the effectiveness of Amadori compounds (suggested as important intermediates in alpha-dicarbonyl formation from carbohydrates) in Strecker aldehyde formation, the amounts of phenylacetaldehyde (PA) formed from either an aqueous solution of L-phenylalanine/glucose or the corresponding Amadori compound N-(1-deoxy-D-fructosyl-1-yl)-L-phenylalanine (ARP-Phe) were compared. The results revealed the ARP-Phe as a much more effective precursor in PA generation. On the contrary, a binary mixture of glucose/phenylalanine yielded preferentially phenylacetic acid, in particular, when reacted in the presence of oxygen and copper ions. Further model experiments gave evidence that a transition-metal-catalyzed oxidation of the ARP-Phe by air oxygen into the 2-hexosulose-(phenylalanine) imine is the key step responsible for the favored formation of phenylacetaldehyde from the Amadori compound. This mechanism might explain differences in the ratios of Strecker aldehydes and the corresponding acids depending on the structures of carbohydrate degradation products involved.
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            Mathematical functions for the representation of chromatographic peaks.

            About ninety empirical functions for the representation of chromatographic peaks have been collected and tabulated. The table, based on almost 200 references, reports for every function: (1) the most used name; (2) the most convenient equation, with the existence intervals for the adjustable parameters and for the independent variable; (3) the applications; (4) the mathematical properties, in relation to the possible applications. The list includes also equations originally proposed to represent peaks obtained in other analytical techniques (e.g. in spectroscopy), which in many instances have proved useful in representing chromatographic peaks as well; the built-in functions employed in some commercial peak-fitting software packages were included, too. Some of the most important chromatographic functions, i.e. the Exponentially Modified Gaussian, the Poisson, the Log-normal, the Edgeworth/Cramér series and the Gram/Charlier series, have been reviewed and commented in more detail.
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              Contribution of mass spectrometry to the study of the Maillard reaction in food.

              The Maillard reaction or non-enzymatic browning corresponds to a set of reactions occurring between amines and carbonyl compounds, especially reducing sugars. The Maillard reaction is known to occur in heated, dried, or stored foods and in vivo in mammalian organisms. In food, the Maillard reaction is responsible for changes in colour, flavor, and nutritive value but also for the formation of stabilizing and mutagenic compounds. Because of the complexity of the Maillard reaction, mass spectrometry, coupled or not to separation techniques, is a key tool in this research area and we will review in this article the contribution of mass spectrometry to the understanding of this reaction. Different steps of Maillard reaction will be described and the importance and the role played by mass spectrometry will be highlighted. In addition, different approaches to investigate the Maillard reaction from the formation of Amadori products (early Maillard reaction product) to the flavor and melanoidin production will also be covered. Copyright (c) 2004 Wiley Periodicals, Inc.
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                Author and article information

                Journal
                J Agric Food Chem
                J. Agric. Food Chem
                jf
                jafcau
                Journal of Agricultural and Food Chemistry
                American Chemical Society
                0021-8561
                1520-5118
                22 August 2013
                25 September 2013
                : 61
                : 38
                : 9015-9026
                Affiliations
                [2]Department of Chemistry, University of Natural Resources and Life Sciences, Vienna , Konrad-Lorenz-Straße 24, A-3430 Tulln, Austria
                Author notes
                [* ](F.L.) Phone: +43-1-47654-6458. Fax: +43-1-47654-6059. E-mail: falk.liebner@ 123456boku.ac.at .
                Article
                10.1021/jf401960m
                3790596
                23967905
                8a50e1db-f54f-436d-942d-57d08617c742
                Copyright © 2013 American Chemical Society
                History
                : 04 May 2013
                : 22 August 2013
                : 21 August 2013
                Categories
                Article
                Custom metadata
                jf401960m
                jf-2013-01960m

                Food science & Technology
                ammoxidation,ammonoxidation,glucose,xylose,humic substances,aminosugars,maillard reaction

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