Arabinogalactans potential

Larch Gum. Larch gum [37320-79-9] (larch arabinogalactan) is obtained by water extraction of the western larch tree, iLarix occidentalism the heartwood of which contains 5—35% on a dry wood basis. In the early 1960s, a countercurrent hot water extraction system was developed, and the gum was produced commercially by the St. Regis Paper Co. under the trade name Stractan. The potential production capacity of this gum is 10,000 t/yr based on the wood residues from the lumber industry. However, the product could not compete with gum arabic, and commercial production is now limited to small batches for a specific medical appHcation. 

FIGURE 1 Potential hydrolysis rates of six structurally distinct polysaccharides in seawater (A) and surface sediments (B) from Skagerrak and Svalbard. Pull = pullulan, lam = laminarin, xyl = xylan, fu = fucoidan, ara = arabinogalactan, chon = chondroitin sulfate. Note the differences in scale on the y axes for sediments and for seawater. [Skagerrak data from Arnosti (2000).]... 

The new water soluble highly stable metal-polysaccharide nanocomposites of noble metals have been fabricated within the framework of the new approach to the synthesis of hybrid nanosized materials on the basis of arabinogalactan. Distinctive optical properties of the nanoparticles are demonstrated as the plasmonic resonance. Nanobiocomposites with target optical characteristics have a great potential to design promising multifunctional materials with controlled optical properties as well as new optical systems and optical markers in medicine. 

Disaccharides have also been synthesized as potential cell wall biosynthesis inhibitors, including analogs of the arabinogalactan linkage disaccharide (O Fig. 22e) [286], and small lipid disaccharides containing arabinose and galactose [287]. Some of these have exhibited moderate in vitro activity against TB. 

The water-extractable arabinogalactans are most abundant in the larches (Larix spp.). The most extensively studied has been that of the heartwood of the western larch Larix occidentalis). The source, production, properties, and potential uses of this polysaccharide are reviewed in Chap. 10.2.2. 

The commercial potential of other extractable carbohydrates has been neither proposed nor promoted for one or more of the following reasons a) they are present in amounts too small to make their extraction economical b) their extraction is difficult c) they are more conveniently and inexpensively obtained from other sources d) the wood is more valuable for purposes other than being chipped and extracted and/or e) they remain undetected as a result of not being sought (see Chap. 4). Larch arabinogalactan is not being utilized currently because no application has been found for which it is uniquely suited - that is, where its cost functionality ratio makes it the gum of choice. 

A survey of the utilization potential of larch arabinogalactan and the current uses of the exudate gums follows. Brief discussions of the utilization of maple sap and sago starch are included with discussions of their occurrence in Chap. 4. 

Larch arabinogalactan is the only carbohydrate known that is a true wood extractive with commercial potential. The polysaccharide, first described in 1898 (7, 34) was originally called epsilon-galactan (29), then larch arabogalactan, and now, more properly, larch arabinogalactan (6). As explained in the preceding section, it is not being utilized at this time because no application for which it would be the gum of choice because of properties or cost has been developed. Its structure (Chap. 4 6, 7, 30, 31, 33-35), production (6, 34), properties (6, 34), and proposed uses (6, 22, 34) have been described and discussed in detail. 

A re-examination of the production, properties, and potential uses of larch arabinogalactan in light of today s needs is needed and could bring it to the market. 

The arabinogalactan saposnikovan C was reported to possess a significant potentiating effect on the reticuloendothelial system in animals. ... 

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