STRUCTURAL STUDIES OF THE PECTIC POLYSACCHARIDE FROM FRUITS OF PUNICA GRANATUM

E.G. Shakhmatov^a, Ph.V. Toukach^b,c, E.N. Makarova^a

^aInstitute of Chemistry, Komi Science Centre, The Urals Branch of the Russian Academy of Sciences, Syktyvkar, Russia
^bN.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia
^cNational Research University Higher School of Economics, Moscow, Russia

KEYWORDS: Punica granatum; Pectic polysaccharides; Arabinan; Arabinogalactan; Structure; NMR

Carbohydrate Polymers, 2020, v. 235, ID 115978

PMID: 32122509, DOI: 10.1016/j.carbpol.2020.115978

The polysaccharide PGO containing 76% of uronic acids, was obtained from peels and membranes of Punica granatum fruits by extraction to the aqueous solution of (NH₄)₂C₂O₄. The chemical structure of PGO was characterized by enzymatic and partial acid hydrolyses, Smith degradation and 1D/2D NMR spectroscopy. It has been found that PGO consisted mainly of highly methyl-esterified and lowly acetylated pectin. Backbone of the macromolecule was represented by 1,4-α-D-GalpA, 1,4-α-D-GalpA(OMe), 1,4-α-D-GalpA(OAc). The branched region PGO contained minor segments of partially acetylated rhamnogalacturonan-I (RG-I). RG-I side chains were comprised of highly branched 1,5-α-L-arabinan and segments of arabinogalactan type I. In addition to pectins, PGO contained the glucuronoxylans and xyloglucans, indicating a close interaction of these polysaccharides with each other in the cell wall. It was concluded that P. granatum fruit could be a promising source of pectic polysaccharides.

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