Pectic galactans

Albersheim64 and coworkers isolated, from pea-stem cell-wall, a fragment composed of the xyloglucan attached to the pectic galactan. Pro-... 

Echinacea-polysaccharide II consists of arabino-3,6-P-galactan part, rhamnogalacturonan part and arabinan part [5], therefore it is suggested that the polysaccharide may be certain ramified region of pectic polysaccharide. 

The present authors and their collaborators have also investigated arabans derived from apple and citrus pectins and here again it is to be noted that the arabans are associated in nature with galactan and pectic acid. The methylated derivatives of all these arabans have very similar properties and on hydrolysis give approximately the same proportions of 2,3,5-trimethyl-L-arabofuranose, 2,3-dimethyl-L-arabinose and... 

Although pectic materials are known to be present in wood, it is not clear whether this e-galactan is a component of wood pectin, and in view of the wide difference in structure between this galactan and the one associated with pectin in lupin seeds, further investigations of this point will be awaited with special interest. 

Alternatively, if we suppose that the hexose polysaccharide is produced first and is then transformed into pectic acid and araban, at least two types of galactan, other than the one already isolated from pectic materials, would be required to account for the types of structure present respectively in pectic acid and araban. This would seem to be somewhat unlikely since, on this view, one would expect to encounter other types of pectic acid and araban, whereas on the evidence now available the pectic acid isolated from all samples of pectic materials examined appears to be the same, and a similar conclusion applies in the case of the araban. 

It will be clear that in this nomenclature arabans and galactans are not included as components of pectinic or pectic acids. They have been found in pectic preparations, but it is not known whether they represent chemically bound constituents such as side chains or are to be regarded as separate substances closely associated physically with the predominating pectinic or pectic acids. The nomenclature is thus based upon an ideal conception and should be regarded as provisional and subject to more accurate specification as knowledge increases. 

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