Isolation, characterisation, and NMR study of xyloglucan from enzymatically depectinised and non-depectinised apple pomace

Xyloglucan extracted with 4 M KOH from enzymically-depectinated and non-depectinated apple pomace was shown to be fucogalactoxyloglucan. The xyloglucan from the enzymically-depectinated apple pomace was found to be of lower molecular weight than that from the non-depectinated pomace. Xyloglucan from the non-depectinated pomace had an intrinsic viscosity of 244 ml/g. The oligosaccharides XXFG and XLFG were isolated from the 1,4-beta-D-glucanase hydrolysate of the xyloglucan and their C-13 NMR spectra were obtained for the first time. Assignment of the anomeric C-13 NMR signals of these oligosaccharides permitted the unambiguous assignment of the anomeric region of the C-13 NMR spectra of the fucogalactoxyloglucan. In the spec tra of the oligosaccharides, splitting was observed in the C-6 signal from the fucosyl residues, indicating their proximity to the reducing glucosyl residues and thus yielding information about the conformation of xyloglucan in solution. Integration of the anomeric signals of H-1 NMR spectra permits the rapid and non-destructive screening of the composition of xyloglucans from different plants. (C) 1999 Elsevier Science Ltd. All rights reserved.