Sugar alcohol

Keto sugar derivatives probably occur as intermediates since the reaction is NAD+-dependent. The pentoses formed may be polymerized to yield arabanes and xylanes which are important cell wall constituents of plants (D 1.4.1). Together with polyuronides (see above) they form the group of hemicelluloses, in which cellulose fibrils (D 1.4.1) are embedded. 

Gander, J. E. Mono- and oligosaccharides. In Plant Biochemistry (J. Bonner, J. E. Varner, eds.), pp. 337-380, Academic Press, New York 1976 

Loewus, F. A. L-Ascorbic acid metabolism, biosynthesis, function. In The Biochemistry of Plants, Vol. 3, Carbohydrates Structurje and Function (J. Preiss, ed.), pp. 77-99. Academic Press, New York 1980 

Loewus, F. A., Tanner, W. (eds.) Plant Carbohydrates I, intracellular carbohydrates (Encyclopedia of Plant Physiology, New Series, Vol. 13 A), Springer, Berlin-Heidelberg-New York 1982 

Sugar alcohols occur in microorganisms, plants, and animals. 

A wide variety of sugar alcohols have been found in plant material (see Chapter V). However, not much is known about the biosynthesis of these compounds. Because the alcohols generally occur together with the structurally related sugars, it has been assumed that mechanisms are available for interconverting them. The following reaction 80), found to occur in animal tissue, may occur in plants  

Cyclic polyalcohols (or cyclitols, according to the nomenclature of sugar alcohols) also have a very low affinity. The most important representative of this class of compounds is inositol, which exhibits a retention behavior comparable to that of pentitols. 

In its weso-configuration, inositol can be phosphorylated. Corresponding procedures for the separation and determination of various inositol phosphates were introduced by Smith and MacQuarrie [209]. 

2 nmol each of myo-inositol (1), glycerol (2), i-erythritol (3), xylitol (4), arabitol (5), sorbitol (6), dulcitol (7), mannitol (8), glucose (9), fructose (10), and sucrose (11). 

1 h using 0.5 mol/L NaOH as the eluent. Interestingly, resolution between glycerol and inositol can be improved by increasing the NaOH concentration, while resolution between mannitol and mannose will be sacrificed. 

In general the chromatographic conditions used for the sugars (section IV, 1) are also suitable for the alditols which migrate in compact zones on buffered [5, 17] or non-buffered [16, 49] layers. Incorporation of boric acid into the silica gel G layers retards the migration of the sugar alcohols [50]. 

The chromatographic conditions used for the sugars (section IV, 1) are suitable for the methyl glycosides which migrate somewhat faster than the free sugars. It is apparent that the a and j8 anomers are readily differentiated and in the few glycosides examined the anomer has the higher hi / value [4, 16]. 

Shasha and Whistler [13] have reported a rapid (12 cm ascent in 10 min) separation of the following methyl a-glycopyranosides on Celite 535-starch with 90% aqueous butanone rhamnose (hi / 88), xylose (hi / 78), galactose (hi / 54), glucose (hi / 50) and mannose (hi / 46). 

In general, these polyols are water-soluble, crystalline compounds with small optical rotations in water and a slightly sweet to very sweet taste. Selected physical properties of many of the sugar alcohols are listed in Table 1. 

Sugar alcohol CAS Registry Number Melting point, °C Optical activity in h2o, [ x]20-25d Solubility g/100gH2Oa Heat of solution, j/gb Heat of combustion, constant vol, kj / molb 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

The small optical rotations of the alditols arise from the low energy barrier for rotation about C—C bonds, permitting easy interconversion and the existence of mixtures of rotational isomers (rotamers) in solution (12). 

The wealdy acidic character of acyclic polyhydric alcohols increases with the number of hydroxyl groups, as indicated by the pKa values in aqueous solution at 18°C (13). 

Sugar alcohol CAS Registry Melting point, °C Optical Solubihty Heat of Heat of 

Obtaiired frorn the Obtained from the reduction of either reduction of either the D-glyceraktehyde or c, carbonyl group of dihydroxyacetone. gilKxjse or the Cj carbonyl group of fnictose. 

D-Sorbitol is abundant in Rosaceae fruits (pomme fruits, stone fruits). For example, its concentration is 300-800 mg/100 ml in apple juice. Since fruits such as berries, citrus fruits, pineapples or bananas do not contain sorbitol, its detection is of analytical importance in the evaluation of wine and other fruit products. Meso-inositol also occurs in fruits in orange juice it ranges from 130-170mg/100ml. 

The lipid content of fruits is generally low, 0.1-0.5% of the fresh weight. Only fruit seeds and nuts contain significantly higher levels of lipids (cf. Table 18.4). The fruit fiesh of avocado is also rich in fat. The lipid fraction of fruits consists of triacylglycerols, glyco- and phospholipids, carotenoids, triterpenoids and waxes. 

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Dowex 2-X8 1.2 0.75 Strongly basic (but less basic than Dowex 1 type) anion exchanger with S-DVB matrix for deionization of carbohydrates and separation of sugars, sugar alcohols, and glycosides. 

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