Contribution of the reaction pathways involved in the isomerization of monosaccharides by alkali

Khadem, Hassan S. El; Ennifar, Sofiane; Isbell, Horace S.

doi:10.1016/0008-6215(87)80238-0

Cited by 42 publications

(24 citation statements)

References 9 publications

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“…[5][6][7] In alkaline aqueous solutions, fructose isomerized to glucose with the highest rate and excellent selectivity. However, the isomerization of mannose was the slowest, and both glucose and fructose were produced almost in the same yield.…”

Section: Mutual Isomerization Of Hexosesmentioning

confidence: 99%

“…However, the isomerization of mannose was the slowest, and both glucose and fructose were produced almost in the same yield. 5) Moreover, mannose isomerized slower than glucose in many ethanolic and methanolic solutions of metal ions. 6,7) Many studies reported that glucose was isomerized to fructose more easily than mannose under alkaline conditions.…”

Section: Mutual Isomerization Of Hexosesmentioning

confidence: 99%

“…25% at 25°C). 5) However, alkali-catalyzed isomerization usually results in many by-products, thus restricting its application. The product distribution in metal-catalyzed isomerization depends on the type of metal ion, saccharides, cosolvents, and metal ion carrier.…”

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confidence: 99%

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Kinetic analysis for the isomerization of glucose, fructose, and mannose in subcritical aqueous ethanol

Gao

Kobayashi

Adachi

2015

Bioscience, Biotechnology, and Biochemistry

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Fructose, glucose, and mannose were treated with subcritical aqueous ethanol for ethanol concentrations ranging from 0 to 80% (v/v) at 180–200 °C. The aldose–ketose isomerization was more favorable than ketose–aldose isomerization and glucose–mannose epimerization. The isomerization of the monosaccharides was promoted by the addition of ethanol. In particular, mannose was isomerized most easily to fructose in subcritical aqueous ethanol. The apparent equilibrium constants for the isomerizations of mannose to fructose, Keq,M→F, and glucose to fructose, Keq,G→F, were independent of ethanol concentration and increased with increasing temperature. Moreover, the Keq,M→F value was much larger than the Keq,G→F value. The enthalpies for the isomerization of mannose to fructose, ΔHM→F, and glucose to fructose, ΔHG→F, were estimated to be 18 and 24 kJ/mol, respectively, according to van’t Hoff equation. Subcritical aqueous ethanol can be used to produce fructose from glucose and mannose efficiently.

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Section: Mutual Isomerization Of Hexosesmentioning

confidence: 99%

Section: Mutual Isomerization Of Hexosesmentioning

confidence: 99%

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Kinetic analysis for the isomerization of glucose, fructose, and mannose in subcritical aqueous ethanol

Gao

Kobayashi

Adachi

2015

Bioscience, Biotechnology, and Biochemistry

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“…Sugars are well known to be unstable in acid and base (17)(18)(19)(20)(21), but there are few data for neutral solutions (22,23). We find that ribose and other sugars have surprisingly short half-lives for decomposition at neutral pH, making it very unlikely that sugars were available as prebiotic reagents.…”

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confidence: 90%

Rates of decomposition of ribose and other sugars: implications for chemical evolution.

Larralde

Robertson

Miller

1995

Proc. Natl. Acad. Sci. U.S.A.

303

175

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The existence of the RNA world, in which RNA acted as a catalyst as well as an informational macromolecule, assumes a large prebiotic source of ribose or the existence of pre-RNA molecules with backbones different from ribose-phosphate. The generally accepted prebiotic synthesis of ribose, the formose reaction, yields numerous sugars without any selectivity. Even if there were a selective synthesis of ribose, there is still the problem of stability. Sugars are known to be unstable in strong acid or base, but there are few data for neutral solutions. Therefore, we have measured the rate of decomposition of ribose between pH 4 and pH 8 from 40°C to 120°C. The ribose half-lives are very short (73 min at pH 7.0 and 100°C and 44 years at pH 7.0 and 0°C). The other aldopentoses and aldohexoses have half-lives within an order of magnitude of these values, as do 2-deoxyribose, ribose 5-phosphate, and ribose 2,4-bisphosphate. These results suggest that the backbone of the first genetic material could not have contained ribose or other sugars because of their instability.The discovery of catalytic RNA (1, 2) gave credibility to previous suggestions that the first living organisms were RNA molecules with catalytic activity (3-7), a concept known as the RNA world (8, 9). We take the RNA world to mean the period before the evolution of protein synthesis when RNA itself contained the genetic information and acted as a catalyst in biochemical reactions. This RNA would have contained a ribose-phosphate backbone with adenine, uracil, guanine, and cytosine (A, U, G, and C) as the bases. It is likely that there was a period before the RNA world, which we will call the pre-RNA world, when living organisms contained a backbone different from ribose-phosphate and possibly bases different from A, U, G, and C. These molecules would still have encoded genetic information and acted as catalysts.There are a number of reasons to believe that the original backbone was not ribose-phosphate, although A, U, G, and C are likely candidates for the bases. First, the polymerization of formaldehyde to sugars, known as the formose or Butlerow reaction, produces almost all possible pentoses and hexoses, including branched-chain sugars, with no selectivity for ribose (10, 11). Also, while the formose reaction works under prebiotic conditions, it is not particularly efficient (12, 13). Another problem is that nucleoside synthesis from the heating of purines with ribose is inefficient and does not work at all with pyrimidines (14, 15). Even if nucleosides could be efficiently synthesized, the products would be racemic, leading to enantiomeric cross-inhibition difficulties in template polymerizations (16).There is an additional problem as severe as any of the above-the stability of ribose. Sugars are well known to be unstable in acid and base (17-21), but there are few data for neutral solutions (22, 23). We find that ribose and other sugars have surprisingly short half-lives for decomposition at neutral pH, making it very unlikely that sugars we...

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“…Many investigators (Beveridg et al, 1982;De Bruijn et al, 1987;El Khadem et al, 1987) have studied the formation of d-psicose by the isomerization of d-fructose in aqueous alkaline solutions. However, those studies were inadequate to explain the formation of psicose in food products, because they did not focus on the formation of psicose during cooking.…”

Section: Introductionmentioning

confidence: 99%

Factors Affecting Psicose Formation in Food Products during Cooking

Oshima¹,

Kimura²,

Kitakubo³

et al. 2014

FSTR

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Introductiond-Psicose (d-ribo-2-hexulose) is a C-3 epimer of d-fructose that is found in fairly small quantities in nature. Because of the small amount of d-psicose present in natural products, few studies have investigated this sugar. Recently, Izumori and his co-workers developed a new method for the large-scale production of d-psicose (Takeshita et al., 2000). The ability to produce large amounts of d-psicose has made it possible to conduct various studies on its use in food. Safety testing of the sugar has verified that d-psicose causes no mutagenesis or acute toxicity (Matsuo et al., 2002). The sweetness of d-psicose is approximately 70% that of sucrose, and little of the sugar is converted to energy in humans . Additionally, d-psicose suppresses blood glucose elevation after eating Iida et al., 2008) and reduces body fat accumulation (Matsuo et al., 2001). Moreover, food products incorporating proteins glycated with d-psicose exhibit excellent antioxidant activity and good rheological properties (Puangmanee et al., 2008;Sun et al., 2006). Hence, the addition of d-psicose as a substitute for alimentary sugars in foodstuffs might be a strategy for developing new functional foods. A syrup containing this sugar is currently on the market.The commercialization of d-psicose as the functional sugar in a food requires that the factors affecting d-psicose formation in food products be clarified, because foods containing a large amount of d-psicose are expected, so the function of the foods must be accurately estimated. Previously (Oshima et al., 2006) we reported that psicose is found in various food products and suggested that the sugar was produced from fructose or sucrose under ordinary heating conditions. Moreover, based on the psicose concentration in food products, we expected that the sugar concentration, heating time, and temperature during the manufacturing process influence the concentration of psicose in food products. Binkley (1963) Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan Received August 11, 2013 Accepted December 14, 2013 Factors affecting the formation of psicose in food products during cooking were investigated based on psicose formation from fructose in various food products and during the caramelization process. Psicose was produced upon heating not only in fructose meringue that had a high fructose content and was alkaline, but also in dried apple that was weakly acidic. Optimized conditions for psicose formation were determined by experiments on fructose caramelization. From the results, we concluded that the following factors affect psicose formation in food products during cooking: high temperatures, high pH, high fructose concentration, and extended cooking time. Of these, the pH of the food was the most important factor for psicose formation in food products.Keywords: psicose, fructose, food products, caramelization, cooking conditions H. Oshima et al. 424 known reaction for the isomerization of sugar. Many investigators (Beveridg et...

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Contribution of the reaction pathways involved in the isomerization of monosaccharides by alkali

Cited by 42 publications

References 9 publications

Kinetic analysis for the isomerization of glucose, fructose, and mannose in subcritical aqueous ethanol

Kinetic analysis for the isomerization of glucose, fructose, and mannose in subcritical aqueous ethanol

Rates of decomposition of ribose and other sugars: implications for chemical evolution.

Factors Affecting Psicose Formation in Food Products during Cooking

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