Constitution of konjac glucomannan:: chemical analysis and 13C NMR spectroscopy

The constitution of konjac glucomannan was determined by methylation analysis and C-13 NMR spectroscopy. The results of methylation analysis showed that the branching point is C-6 carbon of glucosyl units. C-13 NMR spectroscopy (ID and DEPT) of konjac glucomannan supported the presence of beta-C-1-linked C-6 carbon of glucosyl units as the branching units. This result differs from previous investigations. The C-13 NMR spectra indicated that the ratio of terminal glucosyl units to terminal mannosyl units is ca. 2 and branching frequency is ca. 8%, supporting the results by Smith et al. From the splitting of main chain signals the sequences of glucosyl and mannosyl units in konjac glucomannan are estimated and a model structure for the glucomannan is proposed. (C) 2003 Elsevier Science Ltd. All rights reserved.