[Composition and structure of a galactomannan macromolecules from seeds of Astragalus lehmannianus Bunge].
The composition and structure of a galactomannan from seeds of Astragalus 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, [alpha]D, equaled +81.3 degrees; the characteristic viscosity, [eta], 868.4 ml/g). Chemical, chromatographic, and spectral (IR and 13C-NMR spectroscopy) methods were used to demonstrate that the main chain of the molecule is formed by residues of 1,4-beta-D-mannopyranose, 78% of which are substituted at position 6 with single alpha-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 galactomannans was shown to correlate with their content of galactose.
Mestechkina
N M
NM
Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia.
Anulov
O V
OV
Smirnova
N I
NI
Shcherbukhin
V D
VD
D007887:Fabaceae / Q000737:chemistry*; D005690:Galactose / Q000031:analogs & derivatives; D008351:Mannans / Q000737:chemistry*; D010946:Plants, Medicinal
D008351:Mannans; C012990:galactomannan; D005690:Galactose