Carbohydrates oxidation products

Evans, Nicoll, Strause and Waring46 oxidized D-glucose and D-fructose in aqueous solution with excess cupric acetate at 50° for the purpose of ascertaining whether the general principles underlying the mechanism of carbohydrate oxidation in alkaline solutions are sufficient to explain the course of such oxidations in acid solutions. D-Glucosone was claimed to be one of the first products of oxidation the osone was not isolated, and,... 

The first suggestion that substrates in carbohydrate oxidation might exert catalytic effects on the oxidation of other intermediates (cf.earlier demonstration of such action in the urea cycle by Krebs and Henseleit, 1932 see Chapter 6) arose from the work of Szent-Gyorgi (1936). He demonstrated that succinate and its 4C oxidation products catalytically stimulated the rate of respiration by muscle tissues. He also observed that reactions between the 4C intermediates were reversible and that if muscle was incubated with oxaloacetate, fumarate and malate made up 50-75% of the products, 2-oxoglutarate 10-25% and, significantly, 1-2% of the C was converted to citrate. These observations were... 

When the structures of derivatives of the parent compounds depart more and more from those of the original sugars, the bridged-system nomenclature may be advantageously applied over the carbohydrate terms. This could be the case when one, or both, of the OH groups on C-4 and C-8 is (are) absent, as in the deoxy series (see Section V,3), and also in the oxidation products (see Section V,4), where sugar-derived names become complex. 

This chapter deals with the low-molecular weight carbohydrates that can be formally considered as oxidation products of mono- or oligo-saccharides in which an aldehyde group and/or one or more hydroxyl groups have been oxidized to carbonyl and/or carboxyl groups. Some acids are important... 

Many other degradation mechanisms (which are not described here) have been proposed by Isbell and Frush104 in order to account for the various oxidation products formed from carbohydrates by the action of H202. 

Lipid-Protein-Carbohydrate Interactions. Evidence for such complex interaction was recently reported by Huang et al (36) who observed that the addition of corn lipids to zein and corn carbohydrates enhanced the formation of alkylpyrazines, indicating that lipid-derived free radicals may accelerate the rate of Maillard reactions. Two of the alkylpyrazines, identified in such mixtures after heating for 30 minutes at 180°C, have 5-carbon alkyl substitution at the pyrazine ring and could only be explained by interaction of lipid or lipid decomposition products. These authors suggested that condensation of amino ketones, formed by protein-carbohydrate interaction, may yield 3,6-dihydropyrazine which would in turn react with pentanal, a lipid oxidation product, to form 2,5-dimethyl-3-pentylpyrazine. 

These metabolites then are at least partially converted further to oxidized products, conjugates with amino acids or carbohydrates, or other representatives of the remarkable synthetic abilities of organisms (8), although they often are reconverted to the parent metabolite upon return to soil or water. 

Hexa- and Poly-hydric Alcohols and their Oxidation Products. Carbohydrates and Related Compounds, J. K. N. Jones, in E. H. Rodd (Ed.), Chemistry of Carbon Compounds, Vol. IB, Chap. XX, Elsevier, Amsterdam, 1952, pp. 1224-1286. 

Insulin is probably the most important inhibitor of lipolysis. In contrast to adults, in whom catecholamines represent the most important stimulators of lipolysis, thyrotropin (TSH) is the most important stimulator of lipolysis in the newborn. Plasma free fatty acid concentrations rise markedly in the first hours after birth in response to a marked increase in the TSH concentration and a fall in the insulin concentration. The fatty acids released from lipid stores are oxidized by some extrahepatic tissues (e.g., heart and skeletal muscle, kidney, intestine, and lung). Because the respiratory quotient (the ratio of carbon dioxide production to oxygen use) falls from a value of 1.0 (showing that carbohydrate oxidation is the primary source of energy) to a value of 0.8 to 0.9 (showing increasing oxidation of protein or fatty acids) at 2 to 12 hours of age, at a time when protein catabolism is usually insignificant, fatty acid oxidation must represent... 

In an earlier chapter it was found that an oxidation product of making energy from carbohydrates was not only carbon dioxide and water but also a little carbon monoxide. Outline the advantages and disadvantages of having such a compound loose in the body. 

Fig. 2. 23 During early degradation Ej (L) of the leaf titter is kept close to -0.15V allowing for unfractionated recycling of metal ions which got thereby back to the soil interface. Rather than modifying functional groups, C/O (carbohydrate) or C/N (protein) or C/C (polyphenol) backbones extended lines) are cleaved by hydrolysis or oxidation products with broken lines) while the functional groups squares linked to the line(-parts) perpendicularly) remain active towards metal ions round dots)...

The various types of carbohydrates considered in this chapter are shown in formulas I-XVIII. The two ring forms (II and III) of the aldoses are shown because careful oxidation can produce the lactones X and XI directly without breaking the oxygen bridge. In most cases, however, the products of oxidation have been isolated as salts of aldonic acids (IX) thus the nature of the initial oxidation product, either a lactone having the same ring structure as the sugar, or possibly the free... 

Although citrate has been excluded as the primary condensation product of pyruvate and oxalacetate, no direct evidence bearing upon the nature of this product has as yet been obtained. The participation of cfs-aconitic and isocitric acids is speculative. Nor is there any evidence supporting the hypothesis that pyruvate and oxalacetate condense to form a hypothetical intermediate oxalcitraconic acid which can be oxidatively decarboxylated to citric acid. Since citrate, aconitate and isocitrate are in equilibrium with each other, the participation of the last two substances as intermediates of carbohydrate oxidation would, on the surface, appear to be doubtful. Krebs, however, believes that the conversion of cis-aconitate to a-ketoglutarate occurs so rapidly in liver that equilibrium with citrate is not attained. 

Carbohydrates are aldehyde or ketone oxidation products of normal poly-hydroxy alcohols of the same number of carbon atoms, in which one carbon group only is oxidized to aldehyde or ketone, the aldehyde group being the end carbon group and the ketone group being next to the end. 

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