Studies On Extraction, Isolation, Purification And Structure Of Polysaccharides From Flaxseed Hull

In this paper, the extraction, isolation, purification and structure analysis of polysaccharides from flaxseed hull were studied, that provide reference for utilization and exploration of flaxseed. This study mainly composed of three parts. In first part, the location influence of flaxseeds was investigated on content and monosaccharide compositions of crude polysaccharides from different locations, which were under an optimal extraction condition. In second part, a method for large-scale preparation of purified polysaccharide was established, whose structure compositions were determined later. In third part, the structures of purified polysaccharide were studied.Firstly, according to the single factor experiment and comprehensive consideration, the optimal extraction parameters were established as follows: ratio of material to solvent was1:25(w/v), extraction temperature was70℃, duration was40min and extraction repeated two times.Then, the result of GC analysis showed that the monosaccharide compositions of flaxseed polysaccharide fonn three different locations exhibited great variations in chemical compositions. Besides, the variation was mainly reflected by the mole ratio of rhamnose, arabinose and xylose. These results indicated that the locations could influence the ratio of acidic to neutral polysaccharide and the branch number of polysaccharide.Next, the preparation method of large-scale was established for isolation and purification crude polysaccharide of flaxseed hull. One neutral polysaccharide (NP) and two acidic polysaccharides (AP-1, AP-2) were isolated by this method. The molecular weight was determined by HPGPC. The uronic acid was determined by methylation analysis. Functional groups were analyzed by FT-IR spectrum. Monosaccharide composition was determined by GCFinally, based on the data obtained from partial acid hydrolysis, periodate oxidation, smith degradation, methylation analysis, GLC-MS and NMR (ID,2D) analysis, the primary structure of NP and AP-2was identified. AP-1had a mixture structure of NP and AP-2. NP had a (1â†'4)-β-D-xylan backbone structure with significant amounts of doubly branched chains at both the O-2and O-3positions. The side chains arrange potentially random by (1â†'5)-arabinan, araboxylan or other residues (1-Xylp,1-Glcp). AP-2had a backbone structure of repeating dimers of [â†'2)-α-L-Rhap-(1â†'4)-α-D-GalpA-(1â†'], with1-Galp or1-Fucp residues as branch mainly attached at the O-3position of L-Rhap.