Isolation and structural identification of complex feruloylated heteroxylan side-chains from maize bran.
Three complex heteroxylan side-chains acylated with ferulate and one arabinosyl ester of p-coumaric acid have been isolated from maize bran insoluble fibre after acidic hydrolysis and fractionation by gel permeation chromatography and semi-preparative RP-HPLC. The complete structural elucidation of all isolated compounds was achieved by 1D/2D NMR spectroscopy and HPLC-MS in combination with methylation analysis. The absolute configuration of the carbohydrate constituents was determined by chiral GC after acidic hydrolysis and trifluoroacetylation. The identified feruloylated tetrasaccharides alpha-d-xylopyranosyl-(1-->3)-alpha-l-galactopyranosyl-(1-->2)-beta-d-xylopyranosyl-(1-->2)-5-O-trans-feruloyl-l-arabinofuranose (FAXGX) and alpha-d-galactopyranosyl-(1-->3)-alpha-l-galactopyranosyl-(1-->2)-beta-d-xylopyranosyl-(1-->2)-5-O-trans-feruloyl-l-arabinofuranose (FAXGG) are the most complex heteroxylan side-chains from maize bran that have been isolated to date. The isolated trisaccharide alpha-l-galactopyranosyl-(1-->2)-beta-d-xylopyranosyl-(1-->2)-5-O-trans-feruloyl-l-arabinofuranose (FAXG) contributes to the complexity of heteroxylan side-chains from maize bran and 5-O-trans-p-coumaroyl-l-arabinofuranose represents the first p-coumaroylated heteroxylan side-chain isolated from cereal grains. Complex feruloylated heteroxylan side-chains are possibly, like ferulate cross-linking of the heteroxylans and binding of heteroxylans to lignin, a factor contributing to limited enzymatic degradation of fibre.
Allerdings
Ella
E
Institute of Biochemistry and Food Chemistry, Department of Food Chemistry, University of Hamburg, Grindelallee 117, 20146 Hamburg, Germany.
Ralph
John
J
Steinhart
Hans
H
Bunzel
Mirko
M
D003373:Coumaric Acids / Q000737:chemistry*; D004043:Dietary Fiber; D009005:Monosaccharides / Q000737:chemistry*; D011422:Propionates; D014990:Xylans / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry*
D003373:Coumaric Acids; D004043:Dietary Fiber; D009005:Monosaccharides; D011422:Propionates; D014990:Xylans; C004999:ferulic acid; C495469:p-coumaric acid