Structure of acid-extractable polysaccharides of tree greenery of Picea abies

Abstract

The polysaccharide PAA was isolated from tree greenery of spruce Picea abies by the extraction with HCl solution. Monosaccharide analysis PAA revealed high content of uronic acid residues (45%), arabinose (19.5%) and galactose (8.6%). It was shown that this polysaccharide contained polymers of various structures. The major component of which were pectic polysaccharides represented mainly by partly methyl-esterified and partly acetylated 1,4-α-D-galacturonan and by minor parts of partly 2-O- and/or 3-O- acetylated rhamnogalacturonan-I (RG-I). The side carbohydrate chains of the branched region of RG-I were represented predominantly by highly branched 1,5-α-L-arabinan and minor portions of 1,4-β-D-galactan.In addition to the dominant pectins, the isolated polysaccharide also contained arabinogalactan proteins (AGP) and binding glycans of the glucuronoarabinoxylan (GAX), glucomannan (GM) and xyloglucan classes, which indicated a close interaction of these polysaccharides in the cell walls. It can be concluded that, at least a part of the pectin is strongly associated with the AGP and binding glycans of the GAX and GM classes. However, neither GM nor GAX were associated with RG-I.