Pectins rhamnogalacturonan

PR-3 pectin (rhamnogalacturonan 210,000 enhancement of lymphocyte Urtica dioica, roots 1994 [51]... 

Keywords Arabinogalactans Bioactivity Medicinal plants Rhamnogalacturonans Pectins Structure-activity relations... 

The first paper on the bioactive polysaccharides from Glycyrrhiza uralensis roots was published in 1996 by Kiyohara et al. [57]. They isolated a pectic type polymer with anti-complementary and mitogenic activity that was an acidic pectin, possibly containing rhamnogalacturonan type I as part of the total structure. Degradation of the uronic acid part of the molecule decreased both types of bio activities. The neutral oligosaccharide chains were shown to retain some of the activities of the native polymer, but it was suggested that they should be attached to the acidic core to retain maximum activity. 

Arabinofuranosides were removed from PVa, which resulted in an increase in the activity this was in contrast to the findings of Kiyohara et al. [35] who foimd no change in activity after removal of similar units from A. acutiloba pectin. For this polymer it was suggested that the minimum requirement for complement activation via the classical pathway was j6-l,6-linked galactan attached to the rhamnogalacturonan backbone, which also appears to be an important part of the backbone for PVa. 

Pectins are heteropolysaccharides with axial-axial a(1, 4)-D galactopyranosyluronic acid units condensed in the Ci conformation and interrupted by a-(1,2)-L rhamnopyranosyl residues. The structure is based on blocks of galacturonan partly esterified (the smooth zones) and blocks of highly ramified rhamnogalacturonan regions (hairy zones). The exact structure depends on the sources but also on the methods used to isolate the pectins [1,5]. Few data are given in Table 1. 

Other polysaccharides of primary cell walls.-A complex mixture of enzymes including endopolygalacturonase, pectin methylesterase, and/or pectin lyase solubilizes a mixture of polysaccharides from the primary cell walls of fruits [57-64]. Food scientists have referred for some 15 years to this mixture of polysaccharides as the hairy region to describe the highly branched character of the polysaccharides in the fraction and to emphasize the contrast to unbranched homogalacturonan. The recent discovery of rhamnogalacturonan hydrolase [65,66], which selectively cleaves the backbone of RG-I, led to the realization that the hairy... 

Our two network model of the primary wall receives support from a variety of indirect observations. For example it has been shown Aat when a cell wall is regenerated by a carrot protoplast a homogalacturonan/ rhamnogalacturonan shell is laid down first, through which the cellulose/ hemicellulose network is later intercalated (8). Further evidence that pectin may form an independent network is seen in the fact that walls from suspension-cultured cells of tofnato Lycopersicon esculentum VF 36),... 

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