Glucomannan from Narcissus poeticus Studied by PMR and¹³C NMR Spectroscopy

Study on Dendrobium officinale O-acetyl-glucomannan (Dendronan®): Part II. Fine structures of O-acetylated residues

“…4A in the current study or HSQC spectra in previous studies (Rakhimov, Shashkov, Zhauynbaeva, Malikova, & Abdullaev, 2004;van Hazendonk et al, 1996). Besides, the cross-peaks of acetylated C-2/H-2 and acetylated C-3/H-3 of →4)-2,3,6-tri-O-acetyl-␤-d-Manp-(1→ residues (designated M236) were both found in the upper left region of HMBC spectra (Jakes, Yelle, & Frihart, 2011).…”

“…"V" means residue G, M, or M3 in the non-reducing end side. (Rakhimov et al, 2004). The H-5 chemical shift was a little smaller than the reported value, probably due to the effects of neighbouring residues with acetyl groups.…”

“…7), we found evidences for the existence of →4)-6-O-acetyl-␤-d-Manp-(1→ (designated residue M6), →4)-2,6-di-O-acetyl-␤-d-Manp-(1→ (designated residue M26), and →4)-3,6-di-O-acetyl-␤-d-Manp-(1→ (designated M36). Assignments were according to literature data (Rakhimov et al, 2004). The existence of M6 was supported by its strong H-6 /H-6 (4.28 ppm/4.51 ppm) correlation in both COSY (Fig.…”

“…The very downfield chemical shifts of H-2 and H-3 in M236 apparently resulted from the substitution of O-acetyl groups at both O-2 and O-3 position. Furthermore, it was reasonable to deduce that →4)-2,3-di-O-␤-d-Manp-(1→ residues (designated M23) could give rise to C-2/H-2 and C-3/H-3 crosspeaks at the same region of HMQC spectra as M236 did, because of the finding that the absence or presence of an acetyl group at the O-6 position had little effects on the chemical shifts of H-2, H-3, C-2, and C-3 of a 1 → 4 linked ␤-d-Manp residue (Rakhimov et al, 2004). In the current study, aside from C-2/H-2 signal of M2 and C-3/H-3 signal of the M3, there were two more cross-peaks in the upper left region of Fig.…”

Universal fractionation of lignin–carbohydrate complexes (LCCs) from lignocellulosic biomass: an example using spruce wood

“…In this case, the lignin aromatic signals in the 1 H NMR spectrum ( Figure 5) were already very weak due to the short spinspin relaxation time (T 2 ) caused by the large size of the polymers (Zhang and Gellerstedt, 2007). Solid-state 13 C cross polarization-magic angle spinning (CP-MAS) NMR was performed for GML and lignin-free glucomannan (GM) ( Figure 6) in order to overcome the solubility difficulty encountered when performing solution-state NMR, and the assignments for GM are based on previous data (Rakhimov et al, 2004). Here, lignin signals (105-160 ppm for aromatic carbons, approximately 87.5 ppm for lignin sidechain carbons and 55.3 for methoxy carbons) were easily observed by comparison of the 13 C CP-MAS NMR spectra for GML with those for GM.…”