Pectin chemical structure

Rombouts, F.M. and Thibault, J.F. (1986) Sugar beet pectins chemical structure and gelation through oxidative coupUng. In Chemistry and Function of Pectins, edited by M.L. Fishman, et al, pp. 49-60. American Chemical Society, Washington, DC. 

Sugar Beet Pectins Chemical Structure and Gelation through Oxidative Coupling... 

This paper will not described the chemical structure of pectins which is a difficult problem [1] even if the physical properties in solution and ability to form gel must be directly related with the distribution of the units along the chain. The functional properties of pectins are not only related to the neutral sugar content (up to 15 %) but also to the distribution of structural blocks having very different contibutions. 

Interactions studies between some divalents metal ions and pectins from citms and sugar-beet revealed that the chemical structure of the latter, namely the presence of acetyl functions, induces differences of binding process whereas the scale of selectivity was not affected. Some further studies could be carried out on the correlation between the binding mode and the degree of acetylation. Lastly, pectins showed a clear scale of selectivity towards heavy metals with high capacities of binding which make them suitable to be used in waste-waters depollution. 

Fig. 8 Preparation of amphiphilic polysaccharide. Chemical structures of deoxycholic acid-modified chitosan (a) and Phe-modified pectin (pectin-gra/t-Phe) (b). SEM image of nanoparticles prepared from pectin-gra/t-Phe (c)...

Recently two different disciplines, chemical structural elucidation and transmission electron microscopy, were utilized in the study of pectin, with particular emphasis on tobacco pectin. The goal was to help bridge the gap between knowledge of their chemical structures to understanding the complex physical structures revealed by microscopy. To provide background on chemical structure, a study established that tobacco pectin was present as a series of related rhamnogalacturonans. 

Figure 1. Model chemical structure of tobacco pectin.

In conclusion, we have demonstrated that high resolution TEM is a valuable complement to x-ray fiber diffraction analysis and chemical structural elucidation. Its application provided information about the organization of pectin in cell walls and in calcium-free gels. Using freeze-dried samples that were Pt/C replicated, we demonstrated tobacco pectin filaments in a gel to be of the same diameter as the filaments on the noncutinized lower epidermal surface of senescing Coker 319 tobacco leaves. These filaments were 7.1 3A and 4.6 4.8A, respectively, and roughly the same diameter, 7A, as fiber-diffraction modeled citrus pectin (32). Replicated... 

Effect of Chemical Structure of Pectins on Their Interactions with Calcium... 

Compounds with different structures but with the same therapeutic activity isolated from different plant species act as active moieties for the treatment of particular diseases. Some of these compounds have been abandoned due to toxicity but these compounds apparently do not cause serious adverse effects. Some of these active principles originate from edible plants and their inclusion in the diet would undoubtedly be of some value because of their hypocholesterolemic potential. Several phytoconstituents including inulin, pectin, gugglu lipids, flavonoids, ginkoloids, saponins, tannins, and others obtained from various plant sources have proven hypolipidemic potentials as has been further explained in Tables I and II. The chemical structures of a few potential phytoconstituents with hypolipidemic activity are shown in Figure 2. It is hoped that as new additions are made to the list of these active compounds causing only minimum untoward side effects, these naturally... 

For a more detailed discussion of the chemical structure of pectins, see reference... 

Pectin, a structural, cell-wall polysaccharide of all higher plants, like most other polysaccharides, is both polymolecular and polydisperse, i.e., it is heterogeneous with respect to both chemical structure and molecular weight (jl). From molecule to molecule, in any sample of pectin, both the number and percentage of individual monomeric unit types will vary, and the average composition and distribution of molecular weights can vary with the source, the conditions used for isolation, and any subsequent treatments. Because both parameters determine physical properties, various functional types of pectin can be produced by controlling the source, isolation procedure, and subsequent treatment(s)... 

The strong cooperative (4) calcium binding of low-methoxyl pectins may be explained by the stereochemical feature of the 1,4-linked monomeric units (5) leading to the formation of polar cavities which can be occupied by calcium ions, as well as by the chemical structure of the polymer which can be idealized by the juxtaposition of "hairy regions" where the neutral sugcir side-chains are concentrated and of "smooth" regions of unsubstituted homogalacturonans (6,7). 

Much research has been carried out on the chemical structural properties of pectin,8 9 particularly on the composition of the constituent sugars,10 the solution properties,11 the mechanism of gelation12 and the interfacial properties,13 but so far the emulsion-stabilizing properties of depolymerized pectin have received little attention.14... 

In experimentel animals, methylcellulose injection leads to hypertension, due to extensive methylcellulose thesaurosis of the glomerular endothelium (Hall and Hall 1961). Comparable hypertension and nephrotoxicity have been produced by injection of polyvinyl alcohol (Hall and Hall 1965). The pathogenic effects depended more on molecular size than on chemical structure. Similarly, dogs and rabbits injected with pectin showed atheromatous changes and thesaurosis with foam cellular storage phenomena in spleen, liver, and kidneys (Hueper 1942). 

Kowalonek et al. [21] studied pectin/polyvinylpyrrolidone (PVP) blends exposed to ultraviolet radiation and analyzed changes in the chemical structure. These biodegradable blends of natural pectin and synthetic polyvinylpyrrolidone were obtained by casting from aqueous solutions. Figure 1.19... 

Rinaudo M., Effect of chemical structure of pectins on their interactions with calcium, in Plant Cell Wall Polymers Biogenesis and Biodegradation, Eds. Lewis G. and Paice M.G., ACS Symposium Series, American Chemical Society, Washington D.C., 1989, Chapter 23, pp. 324—332. 

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