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 language | English (US) |
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Pages (from-to) | 707-715 |
Number of pages | 9 |
Journal | Journal of agricultural and food chemistry |
Volume | 63 |
Issue number | 2 |
DOIs | |
State | Published - Jan 21 2015 |
Bibliographical note
Publisher Copyright:© 2014 American Chemical Society.
Keywords
- Amaranthus hypochrondriacus
- NMR
- arabinans
- arabinopyranose
- cell wall
- dietary fiber
- galactans
- methylation analysis
- oligosaccharides