The composition and structure of a galactomannan from seeds ofAstragalus lehmannianus, an endemic legume species, is reported for the first time. The purified galactomannan (yield, 4.8%) contained 55% D-mannose and 45%D-galactose and had a molecular weight of 997.03 kDa. Its aqueous solutions were optically active and highly viscous (the specific rotation [α]D equaled +81.3°; the characteristic viscosity [η], 868.4 ml/g). Chemical, Chromatographic, and spectral (IR and13C-NMR spectroscopy) methods were used to demonstrate that the main chain of the molecule is formed by residues of 1,4-β-D-mannopyranose, 78% of which are substituted at position 6 with single α-D-galactopyranose. The distribution of galactose along the chain was calculated from NMR spectra: frequencies of occurrence per pair of neighboring mannose units of ( 1 ) two substituents, (2) one substituent, and (3) no substituents were 65.3%, 31.5, and 3.2, respectively. The specific rotation of the galactomannans was shown to correlate with their content of galactose.
galactose, Galactomannan, apply biochemistry, specific rotation, mannose residue
NCBI PubMed ID: 11042884Publication DOI: 10.1007/BF02731898Journal NLM ID: 0042510Publisher: Kluwer Academic/Plenum Publishers
Institutions: Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia
Methods: 13C NMR, 1H NMR, EI-MS, NMR-2D, TLC, HPLC, extraction, evaporation, centrifugation, HR-EI-MS
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