Structural Studies on Pectin from Marsh Cinquefoil Comarum palustre L.

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R. G. Ovodova¹, O. A. Bushneva¹, A. S. Shashkov², A. O. Chizhov², and Yu. S. Ovodov^1*

¹Institute of Physiology, Komi Science Center, The Urals Branch of the Russian Academy of Sciences, ul. Pervomaiskaya 50, 167982 Syktyvkar, Russia; fax: (7-8212) 241-001; E-mail: ovoys@physiol.komisc.ru

²Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, 119991 Moscow, Russia; fax: (7-095) 135-5328; E-mail: shash@ioc.ac.ru; chizhov@ioc.ac.ru

^* To whom correspondence should be addressed.

Received July 8, 2004; Revision received October 18, 2004

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Pectin with [alpha]_D²⁰ +192° (c 0.1; water), named comaruman, was isolated from marsh cinquefoil Comarum palustre L., which is widespread in the European North. The sugar chain of comaruman contains residues of D-galacturonic acid (64%), D-galactose (13%), L-rhamnose (12%), L-arabinose (6%), and trace amounts of xylose and glucose. Partial acid hydrolysis and digestion with pectinase demonstrated that comaruman composed of the backbone comprised regions of linear alpha-1,4-D-galactopyranosyl uronan interconnected by numerous residues of alpha-1,2-L-rhamnopyranose. In addition to the backbone (core of the macromolecule), ramified regions are involved in comaruman and comprise alpha-2,4-L-rhamno-alpha-4-D-galacturonan with side chains consisting mainly of beta-1,4-linked residues of D-galactopyranose. The ramified region contains additionally residues of 5-O-substituted arabinofuranose and 3- and 6-O-substituted galactopyranose. The present 3,4- and 4,6-di-O-substituted residues of galactopyranose appear to be branching points of the side chains. Some galactopyranose residues were found to occupy the terminal positions of the side chains or appeared to be single sugar residues attached to the side chains. Methylation analysis data indicated that comaruman contains residues of terminal, 3- and 3,4-di-O-substituted galactopyranosyl uronic acid, which appeared to be constituents of the side chains, and the latter represented additionally branching points of the backbone.

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KEY WORDS: plant polysaccharides, pectin, marsh cinquefoil, Comarum palustre L., comaruman, enzymic hydrolysis, NMR spectroscopy of polysaccharides, methylation analysis, GLC-MS of methylated sugars

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