Extraction and structural characteristics of pectic polysaccharides from Abies sibirica L

Abstract Structurally different pectins were isolated from the wood greenery of Abies sibirica L. by the sequential extraction with water (AS W ), HCl solution (pH∼4) (AS A ), and NH 3 solution (pH∼8.5) (AS N ). The GalA/Rha molar ratios for the AS W (15), AS A (8.9), and AS N (3.9) polysaccharides diminish in the order AS W  > AS A  > AS N , indicating a decrease in homogalacturonans and increase in rhamnogalacturonan I in this series. The AS W H, AS A H, and AS N H homogalacturonans derived by acid hydrolysis of AS W , AS A , and AS N have similar Mw 23.8, 21.1, and 18.9 kDa, respectively, corresponding to a mean polymerization degree of 97–122 for the GalA residue. The macromolecule backbone of AS N was represented mainly by moieties of partially methylesterified homogalacturonan and partially 2- O - and/or 3- O -acetylated rhamnogalacturonan I. The carbohydrate side chains of the branched region are primarily made up of terminal, 1,5- O -, 1,3,5-di- O - and 1,2,3,5-tri- O -substituted α-L-Ara f residues and terminal, 1,3- O - and 1,3,6-di- O -substituted β-D-Gal p residues. The currently known pectin models were refined.