Arabinogalactan from larch

Some hemicelluloses have practical applications such as larch arabinogalactan, which is a water-soluble gum found in the heartwood of trees from Larix genus, and which is used in processed food as an emulsifier, or in pudding mixes, etc. A Py-GC/MS study of arabinogalactan from larch wood indicated the presence of the galactose unit and of arabinose unit in the ratio 6 1, as it is known in this material. The arabinose units were identified mainly by the formation of 1,4-anhydro-L-arabinopyranose, which elutes faster than the corresponding hexoses. The structure shown below was therefore confirmed by Py-GC/MS [64]. 

The methods used for structural analysis of (4-0-methylglucurono)xylans have also been applied to the arabinogalactans from larch wood. They include methylation, partial hydrolysis, and Smith degradation. In addition, Barry degradation has found extensive use. Because of the few, detailed, structural investigations so far reported, and because of the complicated nature of the polysaccharides, each of the four species studied will be discussed separately. 

Kg. 24. Partial chemical structure of some hemicelluloses A — 0-acetyl-(4-0-methyl-glucurono)xylan from hardwood B = arabino-(4-0-methylglucurono)xylan from softwood C = 0-acetyl-galactoglucomannan D = arabinogalactan from larch wood (138). 

Dahl K 1970 Recovery of high-purity arabinogalactan from larch. US Patent 3509126... 

The structure (23) has been reported for an arabinogalactan from larch (Larix decidua) The polysaccharide contains residues of D-galactose and L-arabinose in the ratio of 3 1 and has a main chain of (1 3)-linked jS-D-galactopyranosyl residues, to which side-chains of jS-L-arabinofuranosyl residues and of /S-D-galactopyranosyl residues are attached. Most of the pentose occurs as 3-0-/3-L-arabinofuranosyl-L-arabinopyranosyl side-chains. 

Fig. 7 Structure of the Arabinogalactan type II polymer from Larch...

A summary of the yields reported for arabinogalactans from various larches, as well as of their general properties, is presented in Table VIII. 

CAS 9036-66-2 EINECS/ELINCS 232-910-0 FEMA 3254 INS409 Synonyms (+)-Arabinogalactan Arabinogalactoglycan Larch gum Larch turpentine Polyarabinogalactan Stractan Venetian turpentine Classification Natural oleoresin Definition Polysaccharide extracted from Western... 

Antonova G F, Usov A I 1984 Structure of an arabinogalactan from Siberian larch Larix sibirica Ladeb.) wood. Bioorg Khim 10 1664-1669... 

Churms S C, Merrifield E H, Stephen A M 1978 Regularity within the molecular structure of arabinogalactan from Western larch (Larix occidentalis). Carbohyd Res 64 C1-C2... 

Ekman K H, Douglas C 1962 Some physicochemical properties of arabinogalactan from Western larch (Larix occidentalis Nutt.). Tappi 45 477-481... 

Xu L 1984 [Arabinogalactan from two larch timbers - contents, molecular properties, and effects on the setting of cement.] Linye Kexue 20 57-65... 

Ponder, G.R. Arabinogalactan from Western larch. Part IV. Polymeric products of partial acid hydrolysis. Carbohydr. Polym. 36(1), 1-14 (1998)... 

The major D-galactan hemicellulose is an arabinogalactan obtained from softwoods such as larch, black spruce, pine, Douglas fir, cedar, and juniper [72]. Western larch is high in arabinogalactan. The larch arabinogalactans have main chains of D-galactopyranosyl units linked P-1 3 with branch chains of... 

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