Structural studies of arabinan-rich pectic polysaccharides from Abies sibirica L. Biological activity of pectins of A. sibirica

Highly branched arabinan-rich pectic polysaccharides, containing 84% of arabinose, was extracted from wood greenery of Abies sibirica L The structure of arabinan was studied by the 1D and 2D NMR spectroscopy. The macromolecule backbone was represented mainly by RG-I (molar ratio GalA:Rha similar to 1.3:1) patterns with high degree of rhamnose branching. Side chains were comprised of 1,5-linked alpha-L-Araf residues (the major part of polymer mass), 1,3,5-di-O- and 1,2,3,5-tri-O-linked alpha-L-Araf residues, confirming the presence of highly branched 1,5-alpha-L-arabinan. Although most L-Araf were in alpha-anomeric form, minor terminal beta-L-Araf-(1 ->...) was detected. 1,4-beta-D-linked Galp residues found in the side chains account for minor AG-I or 1,4-galactan, as compared to arabinan. A tentative structure was proposed. Polysaccharides obtained from Siberian fir greenery were screened for biological activity. Galacturonan had a strongest stimulating effect on germination and growth rate of seeds, germs and roots of Triticum aestivum, Avena sativa, and Secale cereale. (C) 2014 Elsevier Ltd. All rights reserved.