Glucose-arabinose trisaccharide

For the carbohydrates especially, the amount of available crystal structural data decreases sharply with molecular complexity [479]. With the exception of the cyclodextrins, discussed in Part III, Chapter 18, there are less than 40 crystal structure analyses of oligosaccharides, of which less than 10 are trisaccharides, one is a tetrasaccharide, and one a hexasaccharide (Part III, Chap. 18). The majority of the basic monosaccharides that are the subunits of the polysaccharides that occur naturally have been studied for example, the pyranose forms of /7-arabinose, a-xylose, a- and -glucose, / fructose, a-sorbose, a-mannose, a- and -galactose, a-fucose, a-rhamnose, N-acetyl glucosamine, and mannosamine (Box 13.2). How-... 

Because of the possibility of different -ose and acid substitutions at different positions, the number of anthocyanins is 15-20 times greater than the number of anthocyanidins (Mazza and Miniati, 1993). The -ose molecules most commonly bonded to anthocyanidins are glucose, galactose, rhamnose, arabinose, and di- and trisaccharides, formed by combinations of these four monosaccharides. The most common class of anthocyanins are 3-monosides, 3-biosides, 3,5-diglycosides, and 3,7-diglycosides however, glycosylation of 3, 4, and 5 hydroxyl groups is also possible. The composition and content of anthocyanins in fruits are very diversified (Table 9.5). 

Figure 7. Trisaccharide of glucose and arabinose showing furanose and pyranose structures for the arabinose moiety.

Figure 8. A photograph of a GLC pattern of partially methylated alditol acetates from the trisaccharide of glucose and arabinose. 2,5-A - 1,3,4-tri-O-acetyl-2,5-di-0-methyl arabinitol 2,3,4,6-G - 1,5-di-0-acetyl-2,3,4, 6-tetra-O-methyl glucitol 2,4-A - l,3,5-tri-0-acetyl-2,4-di-0-methyl arabinitol 2,3,6-G - l,4,5-tri-0-acetyl-2,3,6-tri-0-methyl glucitol. (Reproduced with permission from Ref. 30. Copyright 1988 Academic Press.)...

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