Structural characterization of allomelanin from black oat

The brown to black coloration found in plants is due to the melanins, which have been relatively poorly investigated among the plant pigments. The aim of this work was to study the dark pigment extracted from the black oat hull with respect to composition and structure. Ultraviolet-visible (UV-Vis)...

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Bibliographic Details
Main Authors: Varga Mónika
Berkesi Ottó
Darula Zsuzsanna
May Nóra Veronika
Palágyi András
Format: Article
Published: 2016
Series:PHYTOCHEMISTRY 130
doi:10.1016/j.phytochem.2016.07.002

mtmt:3123869
Online Access:http://publicatio.bibl.u-szeged.hu/19375
Description
Summary:The brown to black coloration found in plants is due to the melanins, which have been relatively poorly investigated among the plant pigments. The aim of this work was to study the dark pigment extracted from the black oat hull with respect to composition and structure. Ultraviolet-visible (UV-Vis) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and Fourier transform infrared (FT-IR) spectroscopy were applied for the characterization of the pigment. UV-Vis spectroscopy revealed that the extracted material displays a broadband, structureless absorption profile a common feature of melanins. MALDI-TOF MS measurements demonstrated that oat melanin is a homopolymer built up from p-coumaric acid and consists mainly of low molecular weight (527-1499 Da) oligomers of 3-9 monomer units. The tetramer oligomer proved to be dominant. The results of the FT-IR analysis indicated that oat melanin is a fully conjugated aromatic system containing tetrasubstituted aromatic rings linked by C-C coupling. The in vitro preparation of melanin from p-coumaric acid by horseradish peroxidase was performed for comparison. The resulting polymer consisted of oligomers of 4-9 monomer units similarly to those in oat melanin. However, the building blocks proved to be connected to each other via C-O-C linkages in contrast with the C-C linkages in oat melanin. (C) 2016 Elsevier Ltd. All rights reserved.
Physical Description:313-320
ISSN:0031-9422