2D-HSQC-NMR-Based Screening of Feruloylated Side-Chains of Cereal Grain Arabinoxylans

Abstract

Arabinoxylans of commelinid monocots are characterized by high contents of ferulic acid that is incorporated into arabinose-bearing side-chains of varying complexity. Species-related differences in the feruloylated side-chain profiles of grain arabinoxylans are observed and lead to differences in arabinoxylan functionality. Here, a semi-quantitative assay based on 1H-13C-correlation NMR spectroscopy (HSQC experiment) was developed to profile feruloylated side-chains of cereal grain arabinoxylans. Following acidic liberation of the feruloylated side-chains from the xylan backbone and a clean-up step using C18 solid phase extraction, the feruloylated oligosaccharides FA (5-O-trans-feruloyl-L-arabinofuranose), FAX (β-d-xylopyranosyl-(1 → 2)-5-O-trans-feruloyl-l-arabinofuranose) and FAXG (α-l-galactopyranosyl-(1 → 2)-β-d-xylopyranosyl-(1 → 2)-5-O-trans-feruloyl-l-arabinofuranose) were analyzed by HSQC-NMR. Marker signals were identified for each compound, and experimental conditions such as solvent and internal standard as well as measurement and processing conditions were optimized for a semi-quantitative determination. The approach was validated with respect to accuracy, precision, limit of detection, and limit of quantification. The newly developed approach was applied to several cereal samples including oats, popcorn maize, wheat, and wild rice. Data were compared to an HPLC-DAD/MS approach published earlier by our group, demonstrating that the results of the HSQC approach were comparable to the more time-consuming and technically more challenging HPLC-DAD/MS method.

Molekulare Charakterisierung ferulasäurehaltiger Polysaccharidgele

“…Pastell und Mitarbeiter (2009) konnten das Disaccharid später zusätzlich spektroskopisch in Reis, Weizen und Hafer nachweisen. In Mais wurde nach milder Säurehydrolyse ebenfalls α-d-Xylopyranosyl-(1→3)-l-Arabinofuranose als natives, FS-freies Seitenkettenelement identifiziert (Schendel, 2016).…”

Wheat bran arabinoxylans: Chemical structure, extraction, properties, health benefits, and uses in foods

“…Among the WB layers (i.e., AL, IL, and OP), AX from the AL has the highest level of uXyl p residues (75% of total xylose monomers) (Bacic & Stone, 1981). As xylan chains with a low level of uXylp residues can self‐aggregate easily, the AX in the AL probably is less extractable via water compared to that in starchy endosperm with lower content of uXyl p residues (28% of total xylose monomers) (Schendel, 2016). However, the yield of WEAX from AL was more than that from the whole WB (red and white WB) and showed better antioxidant capacity (Malunga & Beta, 2015; Malunga et al., 2017b).…”

“…Both enzymes are incapable of completely solubilizing the densely substituted regions along the AX backbone, leading to higher A/X ratios in residue AX than the original AX material (Beaugrand, Reis, et al., 2004; Marcotuli et al., 2016). In addition, GH10 xylanases can cleave the glycosidic linkage on the nonreducing end of a xylose substituted with either arabinose or methyl‐glucuronic acid, whereas GH11 xylanases cannot (Pollet et al., 2010; Schendel, 2016). Similarly, the substitution of acetyl groups on the AX backbone partially hinders the endo‐xylanases (Biely et al., 2013).…”

“…The chemical structures of AX in different layers of WB vary in terms of the extent and pattern of substitution of xylose residues with arabinose residues (Delcour et al., 1999; Schendel, 2016; Shiba et al., 1993). AXs also vary in the types of side groups present, such as glucuronic acid, acetyl esters, and feruloylated side chains.…”

“…In earlier studies, AXs are extracted from WB using various methods, resulting in their different chemical structures (Izydorczyk & Biliaderis, 1995; Maes & Delcour, 2002). Typically, the AX from WB has a lower MW than the AX obtained from wheat endosperm (Schendel, 2016). Gel filtration analysis of WEAX from WB shows the MW values ranging from 5 to 50 kDa (Maes & Delcour, 2002).…”