Two-dimensional NMR spectroscopic studies of fenugreek ( Trigonella foenum- graecum L.) galactomannan without chemical fragmentation
Fenugreek galactomannan, as compared to other gums particularly of guar and locust bean, is less exploited in the food industry. With regard to the structure of fenugreek galactomannan, though reports on galactose substitutional pattern are available, supporting data by NMR correlation studies are s...
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Published in | Carbohydrate polymers Vol. 45; no. 1; pp. 69 - 77 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Oxford
Elsevier Ltd
01.05.2001
Elsevier Science |
Subjects | |
Online Access | Get full text |
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Summary: | Fenugreek galactomannan, as compared to other gums particularly of guar and locust bean, is less exploited in the food industry. With regard to the structure of fenugreek galactomannan, though reports on galactose substitutional pattern are available, supporting data by NMR correlation studies are scanty. The present investigation deals with the observations made by 2D NMR spectroscopy of fenugreek galactomannan. Sequential extraction of fenugreek flour with cold water, hot water and alkali resulted in different fractions. Purification of alkali extracted polysaccharide B by copper complex precipitation and GPC (TSK gel) fetched two fractions, viz. Fra.1 and Fra.2 with a gal:man ratio of 1:1.04 and 1:1.12, respectively.
Aspergillus niger β-
d-mannanase had no effect on the hydrolysis of Fra.1 and Fra.2. indicating high substitution and interference by galactose stubs. All the assignments of
1H- and
13C- signals could be achieved and verified through various
1H–
1H and
1H–
13C correlation experiments, viz. DQF-COSY, TOCSY and HSQC. HMBC experiments resulted in correlations of H-1(galα)/C-6(man), H-4(man)/C-1(man) and H-6(man)/C-1(gal). The assignment of anomeric protons and confirmation of (1→4) linked mannan back bone with (1→6) attachment of gal clarified the structure [4)[α-gal-(1→6)]-β-man-(1→]
n
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ISSN: | 0144-8617 1879-1344 |
DOI: | 10.1016/S0144-8617(00)00231-9 |