D-木糖, D-Xylose

D-(+)-Xylose is a monosaccharide. It is enzymatically converted to various intermediates, which are utilized as carbon sources for energy production via several metabolic pathways, including the pentose phosphate and Dahms pathways, by a variety of microorganisms. D-(+)-Xylose has commonly been used as a starting material in the commercial biosynthesis of the non-caloric sweetener xylitol, as well as biofuels, such as ethanol.

D-(+)-Xylose analytical standard provided with chromatographic purity, to be used as reference material for qualitative determination.

D-Xylose, also known as xylose or xylopyranose, belongs to the class of organic compounds known as pentoses. These are monosaccharides in which the carbohydrate moiety contains five carbon atoms. D-Xylose exists as a solid, very soluble (in water), and a very weakly acidic compound (based on its pKa). D-Xylose has been found throughout all human tissues, and has also been primarily detected in saliva, feces, urine, and blood. Within the cell, D-xylose is primarily located in the cytoplasm and lysosome. Outside of the human body, D-xylose can be found in flaxseed. This makes D-xylose a potential biomarker for the consumption of this food product. D-Xylose is a potentially toxic compound.

Aldehydo-D-xylose is a D-xylose. It has a role as a human metabolite and a Saccharomyces cerevisiae metabolite.

Xylose is a monosaccharide of the aldopentose type consisted of five carbon atoms and an aldehyde functional group. Xylose is a sugar isolated from wood. D-Xylose is a sugar widely used as a diabetic sweetener in food and beverage. Xylose has also been used as a diagnostic agent to observe malabsorption. Reduction of xylose by catalytic hydrogenation produces the common food additive sweetener substitute xylitol [DB11195]. The dextrorotary form of xylose, D-xylose, refers usually to the endogenously occurring form of the sugar in living things. The levorotary form, L-xylose, can refer to the form that is synthesized. Nevertheless, xylose by itself may not necessarily serve many purposes immediately - but its metabolism results in a variety of substrates that can serve important nutritional and biological purposes.

Prod. industrially by hydrol. of wood. Found mainly in the form of Xylan or as glycosides. Present in wood (maple and cherrry), straw, corncobs, cotton seed hulls and pecan shells. Sweetener. Inexpensive starting material for synthesis.

Diagnostic aid (intestinal function determination). Needles (EtOH). Mp 1538 (144-1458). [a]20 D +19 (H2O, equilib.). Weak sweet taste.

Title: Xylose

CAS Registry Number: 58-86-6

CAS Name: D-Xylose

Additional Names: wood sugar

Trademarks: Xylomed (Bio-Medical); Xylo-Pfan (Savage)

Molecular Formula: C5H10O5

Molecular Weight: 150.13

Percent Composition: C 40.00%, H 6.71%, O 53.29%

Literature References: Widely distributed in plant materials, especially in wood (maple, cherry), in straw, in hulls. Not found in free state, but in form of xylan, a polysaccharide built from D-xylose units and occurring in association with cellulose. Xylose occurs also as part of glycosides. Isoln from corn cobs by boiling with 8% H2SO4: Monroe, J. Am. Chem. Soc. 41, 1002 (1919). Peanut shells and cottonseed hulls also are practical sources of xylose: Ling, Nanji, J. Chem. Soc. 1923, 620. Configuration: Hudson, Yanovsky, J. Am. Chem. Soc. 39, 1029 (1917); Haworth, Nature 116, 430 (1925). Review on history, constitution and prepn: Harding, Sugar 24, 14 (1922).

Properties: Monoclinic needles or prisms. Very sweet taste. mp 144-145° (Wheeler, Tollens, Ann. 254, 309); mp 153-154° (Hébert, Compt. Rend. 110, 970). d420 1.525. Shows mutarotation. [a]D20 +92° ® +18.6° (16 hrs c = 10). One gram dissolves in 0.8 ml water. Sol in pyridine, hot alcohol. pKa (18°): 12.14. Reduces warm Fehling's soln. Upon heating with water in closed tube to 140° or by boiling with dil H2SO4, furfurol is formed.

Melting point: mp 144-145° (Wheeler, Tollens, Ann. 254, 309); mp 153-154° (Hébert, Compt. Rend. 110, 970)

pKa: pKa (18°): 12.14

Optical Rotation: [a]D20 +92° ® +18.6° (16 hrs c = 10)

Density: d420 1.525

Use: In tanning, dyeing, and as a diabetic food.

Therap-Cat: Diagnostic aid (intestinal function).

Keywords: Diagnostic Aid.