We have previously reported [1 ] that the shell of Gleditsia texana seeds contains 23.7% water-soluble polysaccharides (WSPS), mainly galactomannan. The isolated polysaccharide is a white amorphous powder that dissolves in water to give a viscous gel (rlcha r = 9.87), specific rotation [~lo 2~ = +14" (c 0.1; H20). Sedimentation analysis indicates that the starting galactomannan was polydisperse.Fractionation of a 0.25% aqueous solution of WSPS by alcohol gave three fractions ( Table 1). The polysaccharide fractions consist of galactomannans that differ in the ratio of mannose units, viscosity, and degree of polymerization (DP). The quantitative content of fraction I was the greatest (88.5%). The sedimenogram showed that it was homogeneous. Therefore, fraction I was further investigated chemically.The configuration of the glycoside bond was determined by oxidizing the fully acetylated galactomannan with CrO 3. The detection of only galactose confirms that the glycoside of this component has the o~-configuration.The bonding type of the monomers and the size of the heterocyclic ring were determined by Smith degradation. The hydrolysate of oxidation products contained erythrit and glycerin in an 11.3:3.4 ratio according to paper chromatography (PC) and GLC. A total of 1.05 moles of periodate released 0.28 moles of formic acid. The appearance of erythrit indicates that the mannose and galactomannan residues are 1-,4 bonded. The presence of 2,3,6-tri-O-methyl-D-mannose confirms that the mannopyranose units are linked by a 144 glycoside bond. The detection of 2,3-di-O-methyl-D-mannose indicates that the structure is branched with a galactomannan side chain containing a galactose bonded to a C-6 mannose.The sequence of sugar units in the macromolecule was studied by partial acid hydrolysis (0.25 M CF3COOH, 3 h). Free galactose, mannose, and lbur oligosaccharides (A-D) with R.f values 0.72 (A), 0.56 (B), 0.27 (C), and 0.08 (D) were identified by PC using butanol-pyridine-water (6:4:3).Acid hydrolysis of the oligosaccharides and their reduction products (NaBH 4) showed that oligosaccharide A is mannobiose; B. galactosylmannose; C, mannotriose; D, mannotetraose.The galactomannan from G. tevana seeds differs from that from Gleditsia sp. that was studied earlier [3-51 in the ratio of monomers, DP, molecular mass (MM), and the degree of substitution in the 13-D-mannan main chain by D-galactose units.
UDC 547.917Galactomannans isolated fi'om the seeds ofGleditsia macracantha (GMM) and Gleditsia texana (GMT) have molecular masses (MM) of" 750,000 and 795,000 and galactose to mannose ratios of 1.0:4.9 and 1.0:3.8. respectively. GMT and GMM are depolymeri:ed to fragments of MM 25 and 19 kDa with retention of the primaly structure and are studied ILv 13C NMR spectroscolLv. The principal chains of GMM and GMT are fl-l-4-mannopyranose residues in which the hydro.~3'l groups of" C-6 are substituted by single a-D-galactopyranose traits.We previously reported a study of carbohydrates and proteins isolated from seeds of the large-thorned locust (Gleditsia maeracantha) [ I ]. The goal of the present work was to isolate galactomannans from G. macracantha and G. texana and to establish their primary structure using 13C NMR spectroscopy.Aqueous extracts of the ground husk from seeds of both species were precipitated with ethanol. Water-soluble polysaccharides (WSPS) were obtained in yields of 21 and 23.7%, respectively. Hydrolysates of the WSPS were examined by GLC. Galactose and mannose were fbund in the ratios 1.0:4.9 (G. macracantha) and 1.0:3.8 (G. texana). Therefore, the WSPS are galactomannoses and are designated as GMM (G. macracantha) and GMT (G. texana).The IR spectra of GMM and GMT contain absorption bands similar to those in the spectra of known 1,4-[3-mannosecontaining polysaccharides [2, 3]. Absorption bands are observed at 900, 870, 820, and 720 cm t in the low-frequency region. Of these, the first three indicate the presence of mannose, the 13-configuration of the anomeric centers, and the pyranose ring, -~)
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