Structural characterization of allomelanin from black oat

Mónika Varga, O. Berkesi, Z. Darula, Nóra Veronika May, András Palágyi

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

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.

Original languageEnglish
JournalPhytochemistry
DOIs
Publication statusAccepted/In press - Mar 26 2016

Fingerprint

Melanins
melanin
oats
Oligomers
Pigments
ultraviolet-visible spectroscopy
Spectrum Analysis
matrix-assisted laser desorption-ionization mass spectrometry
p-coumaric acid
Ultraviolet visible spectroscopy
Ionization
Mass spectrometry
aromatic compounds
Desorption
Mass Spectrometry
Lasers
Monomers
pigments
plant pigments
electron paramagnetic resonance spectroscopy

Keywords

  • Avena sativa (Poaceae)
  • FT-IR spectroscopy
  • MALDI-TOF MS
  • Melanin
  • Oat
  • p-Coumaric acid

ASJC Scopus subject areas

  • Plant Science
  • Biochemistry
  • Molecular Biology
  • Horticulture

Cite this

Structural characterization of allomelanin from black oat. / Varga, Mónika; Berkesi, O.; Darula, Z.; May, Nóra Veronika; Palágyi, András.

In: Phytochemistry, 26.03.2016.

Research output: Contribution to journalArticle

Varga, Mónika ; Berkesi, O. ; Darula, Z. ; May, Nóra Veronika ; Palágyi, András. / Structural characterization of allomelanin from black oat. In: Phytochemistry. 2016.
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