Neutral pectin side chains of Amaranth (Amaranthus hypochondriacus) contain long, partially branched arabinans and short galactans, both with terminal arabinopyranoses

Daniel Wefers, Catrin E. Tyl, Mirko Bunzel

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Amaranth is a pseudocereal of high nutritional value, including a high dietary fiber content. Amaranth dietary fiber was suggested to contain large amounts of neutral rhamnogalacturonan I side chains. In this study, endo-arabinanase and endo-galactanase were used to liberate arabinan and galactan oligosaccharides from amaranth fiber. The liberated oligosaccharides were identified by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and HPLC-MSn using standard compounds, which were isolated from amaranth, sugar beet, potato, and red clover sprouts and characterized by one- and two-dimensional NMR spectroscopy. It was demonstrated that insoluble amaranth arabinans have linear and branched areas, with the O-3 position being the dominant branching point. Minor amounts of branches at position O-2 and double substitution were also found. Amaranth arabinans were also demonstrated to contain terminal α-(1→5)-linked l-arabinopyranose units. In addition, it was evidenced that galactans from amaranth seeds are composed of β-(1→4)-linked d-galactopyranose units, which can also be terminated with l-arabinopyranose units. In direct comparison to structural elucidation of amaranth fiber by using methylation analysis, the advantage of the enzymatic approach over methylation analysis was demonstrated.

Original languageEnglish (US)
Pages (from-to)707-715
Number of pages9
JournalJournal of agricultural and food chemistry
Volume63
Issue number2
DOIs
StatePublished - Jan 21 2015

Keywords

  • Amaranthus hypochrondriacus
  • NMR
  • arabinans
  • arabinopyranose
  • cell wall
  • dietary fiber
  • galactans
  • methylation analysis
  • oligosaccharides

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