Sugar alcohols ribitol

As shown in Figure 7.1, riboflavin consists of a tricyclic dimethyl-isoalloxazine ring conjugated to the sugar alcohol ribitol. The metabolically active coenzymes are riboflavin 5 -phosphate and flavin adenine dinucleotide (FAD). In some enzymes the prosthetic group is riboflavin, bound covalently at the catalytic site. 

Riboflavin, also known as vitaniin B2, gets its name from its sugar alcohol (ribitol), and from its yellow color and its fluorescence under UV light (flavin comes from the Latin word for yellow). Its systematic names are 7,8-dimethyl-... 

Cytidine phosphates cytidine S -monophosphate (CMP, cytidylic acid, M, 323.2), cytidine 5 -diphos-phate (CDP, M, 403.19) and cytidine 5 -triphosphate (CTP, M, 483.16). For structure, see e. g. Pyrimidine biosynthesis. CTP is a precursor of RNA synthesis, while deoxy-CTP is a precursor of DNA synthesis. CDP may be regarded as the coenzyme of phospholipid biosynthesis (see Membrane lipids) (activated choline is CDP-choline). Glycerol and the sugar alcohol, ribitol, are also activated by bonding to CDP (see Nucleoside diphosphate sugars). Reduction of ribose... 

Riboflavin differs from all other nucleosides in being a derivative of the sugar alcohol, ribitol. A specific kinase has been found that produces the nucleotide, FMN, from riboflavin and ATP, ... 

Yellow (hence the name) prosthetic groups,//av/w adenine dinucleotide (FAD) and the somewhat less common flavin mononucleotide (FMN) are linked to protein in flavoproteins (Fig. 29), The nomenclature is not quite accurate since 6,7-dimethyl-isoalloxazine, which is responsible for the color, is not linked to ribose, as in the nucleotides, but to the corresponding sugar alcohol ribitol. In both FAD and FMN the 6,7-dimethyl-... 

Sweetness is often an important characteristic of sugar alcohols in food and pharmaceutical applications. The property of sweetness is measured in a variety of ways and has a corresponding variability in ratings (218). Based on one or more test methods, erythritol and xyfitol are similar to or sweeter than sucrose (218,219). Sorbitol is about 60% as sweet as sucrose, and mannitol, D-arabinitol, ribitol, maltitol, isomalt, and lactitol are generally comparable to sorbitol (see Sweeteners). 

Mannitol hexanitrate is obtained by nitration of mannitol with mixed nitric and sulfuric acids. Similarly, nitration of sorbitol using mixed acid produces the hexanitrate when the reaction is conducted at 0—3°C and at —10 to —75°C, the main product is sorbitol pentanitrate (117). Xylitol, ribitol, and L-arabinitol are converted to the pentanitrates by fuming nitric acid and acetic anhydride (118). Phosphate esters of sugar alcohols are obtained by the action of phosphorus oxychloride (119) and by alcoholysis of organic phosphates (120). The 1,6-dibenzene sulfonate of D-mannitol is obtained by the action of benzene sulfonyl chloride in pyridine at 0°C (121). To obtain 1,6-dimethanesulfonyl-D-mannitol free from anhydrides and other by-products, after similar sulfonation with methane sulfonyl chloride and pyridine the remaining hydroxyl groups are acetylated with acetic anhydride and the insoluble acetyl derivative is separated, followed by deacetylation with hydrogen chloride in methanol (122). Alkyl sulfate esters of polyhydric alcohols result from the action of sulfur trioxide—trialkyl phosphates as in the reaction of sorbitol at 34—40°C with sulfur trioxide—triethyl phosphate to form sorbitol hexa(ethylsulfate) (123). 

Although the ribitol moiety is not involved in the redox function of the flavin coenzymes, both the stereochemistry and nature of the sugar alcohol are important. Although some riboflavin analogs have partial vitamin action. 

Properties and Occurrence of Free Sugar Alcohols, D-Glucitol, D-Mannitol, RIbItol, Xylltol, and n-Arablnltol... 

The solution and solid state structures of the following sugar alcohols are discussed in separate sections erythritol 1, D-threitol 2, xylitol 3, D-arabitol 4, ribitol 5, D-mannitol 6, dulcitol 7, and D-sorbitol 8. 

These compounds are derived from the vitamin riboflavin. They are not true nucleotides, because the flavin ring system is attached to ribitol, a sugar alcohol, rather than ribose. 

Figure 8.8. Separation of various sugars and sugar alcohols on a Coregel-87C column. Analysis Conditions Column Transgenomic Coregel-87C Eluent Distilled water Flow rate 0.6 mL/min Temperature 8.5 °C Pressure 425 psig Detection R1 range 8x Injection 20 jiL. Sample 1. raffinose, 2. sucrose, 3. lactulose, 4. glucose, 5, galactose, 6. fructose, 7. ribitol, 8. mannitol, 9. sorbitol.

Gram-positive bacteria also have additional anionic polymers (secondary cell-wall polymers, SCWPs), which are covalently attached to the muramic acid residues of the peptidoglyean and attach cell-surface proteins. They can be of the teichoic acid type, linear copolymers of a sugar alcohol and phosphoric acid, or the teichuronic acid type, in which the anionic component is uronic acids.The commonest teichoic acids are based on 1,3-linked glycerol or 1,5-linked ribitol. 

N. Lotong, and K. Matsushita, Membrane-bound sugar alcohol dehydrogenase in acetic add bacteria catalyzes L-ribulose formation and NAD-dependent ribitol dehydrogenase is independent of the oxidative fermentation, Biosci. Biotechnol. Biochem., 65 (2001) 115-125. 

If the aldehyde or ketone functions of aldoses or ketoses respectively are reduced to alcohols the molecules produced have open-chain structures and are called sugar alcohols. They are denoted by the end -itol . Hence that derived from ribose is ribitol, that from mannose is mannitol and so on. They are chiefly encountered in bacterial polymers. 

Hgure 3 Chromatogram in GC of a standard solution of ten sugar alcohols. Peaks are s = solvent front 1 =erythreitol 2 = pentaerythreitol 3 = ribitol 4 = arabitol 5=xylitol 6 = man-annitol 7 = galactitol 8=sorbitol 9 = inositol 10 = perseitol. The retention time of pentaerythreitol was 4 min. 

Ribitol an optically inactive, Cj-sugar alcohol, bio- thesized by reduction of ribose. M.p. 102°CR. is... 

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