Structural characteristics of oxalate-soluble polysaccharides from Norway spruce (Picea abies) foliage

•The oxalate-extractable pectin (PAO) were isolated from P. abies greenery.•PAO core consists of 1,4-α-GalpA, 1,4-α-GalpA(OMe), and 1,4-α-GalpA(OAc).•RG-I side chains are formed of branched 1,5-α-l-arabinan and arabinogalactan type I.•RG-I regions alternate with non-acetylated and non-methyl-esterified galacturonan.•PAO fraction also contained of the xylan and glucomannan. Structurally different polymers were derived from Picea abies foliage by successive extraction with water (PAW), HCl solution (PAA) and (NH4)2C2O4 solution (PAO). The P. abies foliage was found to contain basically low-methoxyl pectin extractable with an (NH4)2C2O4 solution. PAW was shown to comprise primarily arabinogalactan-proteins (AGPs); PAA was composed of mixed AGPs and pectic polysaccharides, with the latter prevailing; and polysaccharide PAO isolated in the highest yield included chiefly pectic polysaccharides. The major constituents of PAO were low-methoxyl and low-acetylated 1,4-α-d-galacturonan and partially acetylated RG-I. The sugar side chains of RG-I contained chiefly highly branched 1,5-α-l-arabinan and arabinogalactan type I as a minor constituent. RG-I whose side chains had 1,5-α-l-arabinan represented short regions alternating with non-acetylated and unmethylesterified galacturonan regions. In addition to pectins, polysaccharide PAO contained AGPs, xylanes and glucomannans, indicating that these polysaccharides are in an intimate interaction.