Arabinose solution

Figure 2. Enzymic measurement of a-L-arabinan in fruit-juice concentrates, (a) Effect of time of incubation of sample with arabinofuranosidase and ndo-arabinanase. Diluted pear juice concentrate (1 10 0.1 ml) or sugar beet arabinan solution (0.1 ml) was incubated with an aliquot (0.1 ml) of arabinofuranosidase (5 units) plus ndo-arabinanase (0.2 units) at 35 C and pH 4.0. Aliquots were analysed for arabinose. (b) Arabinose determination using the NAD-Galactose Dehydrogenase method. Arabinose solution (0.2 ml, 50 digrams) was incubated with Tris-HCl buffer (2.5 ml, pH 8.6), NAD (0.1 ml, 10 m ml) and galactose dehydrogenase (20/i, 140 milliunits) at 35°C. Absorbance (340 nm) was measured after various time intervals.

For arabinose the half-times for all components are essentially the same. As long as this constraint is obeyed, the calculated optical rotation curves would be expected to show no rapid initial drop, and this is what was found. Therefore, we must postulate a fifth, as yet undetected, fast component in mutarotating arabinose solutions. Here the only reasonable... 

K. is produced by the aerobic fermentation of glucose, glycerol, arabinose solutions and liom a wide range of other carbon sources with Aspergillus sp. K. shows some antibiotic and weak insecticidal activity. It has been converted to - maltol and ethyl maltol as flavor-enhancing additives. 

The approximate times of osazone formation in minutes are given in Table 111,139. The product from mannose is the simple hydrazone and is practically white. Arabinose osazone separates first as an oil, whilst that from galactose is highly crystalline. Lactose and maltose give no precipitate from hot solution. 

The reaction is used for the chain extension of aldoses in the synthesis of new or unusual sugars In this case the starting material l arabinose is an abundant natural product and possesses the correct configurations at its three chirality centers for elaboration to the relatively rare l enantiomers of glucose and mannose After cyanohydrin formation the cyano groups are converted to aldehyde functions by hydrogenation m aqueous solution Under these conditions —C=N is reduced to —CH=NH and hydrolyzes rapidly to —CH=0 Use of a poisoned palladium on barium sulfate catalyst prevents further reduction to the alditols... 

Gum ghatti is the calcium and magnesium salt of a complex polysaccharide which contains L-arabinose, D-galactose, D-mannose, and D-xylose and D-glucuronic acid (48) and has a molecular weight of approximately 12,000. On dispersion in water, gum ghatti forms viscous solutions of viscosity intermediate between those of gum arabic and gum karaya. These dispersions have emulsification and adhesive properties equivalent to or superior to those described for gum arabic. 

Detection and result The chromatogram was freed from mobile phase and immersed in the reagent solution for 1 s and then heated to 130°C for 10 min. Rhamnose (JiRf 35—40) and fructose hRf 70—75) yielded brown and xylose (JhRf 45 — 50) and arabinose (hRf 60—65) red-brown chromatogram zones on a pale background. The detection limit for the pentoses was 0.1 pg and for fructose it was 0.5 pg substance per chromatogram zone. 

The solution is transferred to a 3-I. flask, using about 50 cc. of water for rinsing, and to it is added, with violent (Note 6) shaking, twice its volume (1400-1500 cc.) of 95 per cent ethyl alcohol. The solution is decanted from the gummy residue and the latter extracted three times with methyl alcohol under reflux, each time with 500 cc. of the solvent. In order to remove all the arabinose from the salts the precipitate is dissolved in 200-220 cc. of water, transferred to an evaporating dish, and 400 cc. of 95 per cent ethyl alcohol is stirred in with a heavy rod. The clear alcohol solution is decanted and the solid triturated twice with 300 cc. portions of methyl alcohol. 

All the alcoholic extracts (both ethyl and methyl) are combined, shaken thoroughly, and 95 per cent ethyl alcohol added as long as any appreciable precipitate forms (Note 7). The solution is allowed to stand for some hours until it is clear, decanted, and concentrated in vacuo on a boiling water bath to a thin syrup (Note 8). Crystallization usually begins as soon as the syrup is cool though it is sometimes necessary to seed with arabinose. 

Method B (one-pot procedure)-. 5 g (33 mmol) of L-arabinose. 12 mL of ethanol and 4mL (36.7 mmol) of bcnzylaminc arc heated on a steam bath for 5 to 10 min to give a clear solution. After cooling, 2.5 mL of anliyd hydrogen cyanide are added. Spontaneous crystallization of the product begins within a few minutes. After cooling for 2 h with an ice-bath, the product is isolated by filtration and washed with ethanol yield 7.0-7.5g (79-85%) nip 129-131 C after recrystallization from ethanol mp 130-132 C. 

Neutral solutions of pure aldoses exhibit no selective absorption in the ultraviolet region103 106 such an absorption may, however, be observed108 for solutions of D-glucose and L-arabinose in 50% sulfuric acid, and is... 

The procedure that Kuhn and Baschang99 had reported for the synthesis of NeuAc was extended by Hershberger and Binkley100 to a synthesis of KDO, as follows. Condensation of di-ter -butyl oxalacetate (85 see Scheme 25) with D-arabinose gave the epimeric mixture of lactone esters, 86 and 87, which was separated by fractional recrystallization. When 86 was heated in aqueous solution, the enol lactone, 88, was produced from 87, an enol lactone diastereomeric with 88 was obtained under these conditions. Compound 88 was converted into ammonium KDO by treatment with aqueous ammonia. 

After the reaction mixture has been dissolved in water and acidified, the hydrogen cyanide should be removed as soon as possible, for the arabinose tends to react with it even in dilute solution. 

A further quantity of arabinose may be isolated from the mother liquors by the use of diphenylhydrazine to a solution of 22 g. of diphenylhydrazine hydrochloride in 100 cc. of absolute methyl alcohol is added a solution of 3.3 g. of sodium in 50 cc. of methyl alcohol. After fifteen minutes standing the sodium chloride is removed by filtration and washed with methyl alcohol. The filtrate, which contains approximately 18 g. of free diphenylhydrazine, is added to the alcoholic mother liquor from the arabinose and the mixture is inoculated with diphenylhydrazone prepared from some of the crystalline arabinose. The mixture is allowed to stand overnight, and the crystalline diphenylhydrazone is filtered, washed with 95 per cent ethyl alcohol, and dried in a vacuum desiccator. In a preparation in which the yield of crystalline arabinose had been 23.5 g., the yield of diphenylhydrazone was 16.5 g., corresponding to 7.8 g. of the sugar. Arabinose can be recovered from the diphenylhydrazone by treatment with formaldehyde in aqueous solution. In view of the... 

Both D-[l- C]xylose and D-[5- C]arabinose were exposed to a concentrated phosphate buffer solution (pH 6.7). 1-Hydroxy-2-propanone (ace-tol) was distilled from the heated solution. Radioassay indicated that similar labeling [3- C] occurred in the acetol from both pentoses, with loss of the configurational difference thus, a 3-ketopentose or its enediol was suggested as an intermediate. Further work with 3-0- and 6-0-methyl-D-glucose and with 1-0-methyl-D-fructose indicated that /3-elimination from a 3-ketose or, in the case of a hexose, from a 3-ketose or a 4-ketose, or both, tautomerization of the resulting a-diketone to a /3-diketone, and hydrolytic cleavage are essential steps in the formation of acetol. 

Most studies were performed with hyperosmolar solutions. Hypertonic disruption is under clinical evaluation for enhanced delivery of small molecular weight cytostatic agents to brain tumours. Technically, the procedure is performed as a high-flow short-term infusion of 25% mannitol or arabinose under general anaesthesia. The underlying mechanism is a sequelae of endothehal cell shrinkage, disruption of tight junctions and vasodilatation by osmotic shift [72]. 

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