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NMR analysis of tri‐ and tetrasaccharides from asparagus
Author(s) -
Fukushi Eri,
Onodera Shuich,
Yamamori Akira,
Shiomi Norio,
Kawabata Jun
Publication year - 2000
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/1097-458x(200012)38:12<1005::aid-mrc772>3.0.co;2-q
Subject(s) - chemistry , anomer , fructose , carbon 13 nmr , proton nmr , nuclear magnetic resonance spectroscopy , asparagus , heteronuclear single quantum coherence spectroscopy , methylene , stereochemistry , organic chemistry , botany , biology
Detailed analysis of the 1 H and 13 C NMR spectra of five fructo‐oligosaccharides ( 1–5 ) isolated from Asparagus officinalis L. (Liliaceae) was carried out. Tetrasaccharides 1 , 2 and 3 consist of one unit of glucose and three units of fructose, whereas trisaccharides 4 and 5 consist of one unit of glucose and two units of fructose. The 1 H NMR signals of these tetrasaccharides were severely overlapped around δ H 3.6–4.0 ppm and the 13 C NMR signals of the corresponding signals of three fructose residues were close to each other. Therefore, it was difficult to make assignments of those signals using conventional NMR methods. Overcoming these signal‐overlapping problems required the application of some special NMR techniques. The spectral analysis was started from the anomeric proton of the glucose, since each compound had only one glucose residue and its 1 H NMR spectrum showed a separate characteristic anomeric proton signal. After the 1 H and 13 C signals of the glucose had been assigned, the fructose residues attached to the C‐1 and/or C‐6 positions of glucose were determined from the HMBC spectrum, which also revealed further fructosyl fructose linkages. The assignments of each signal of C‐5 and C‐6 of the fructose residues overlapped in 2D spectra were achieved by the 1D INAPT method. Unresolved correlation peaks of methylene protons in HMQC could be separated by the CH 2 ‐selected HSQC method, which gave sufficient 13 C resolution to separate each CH 2 signal, resulting in the determination of the chemical shift of the methylene protons. Copyright © 2000 John Wiley & Sons, Ltd.