Sugar carboxylic acids

Oxidation of aldoses yields aldonic acids (onic acids), uronic acids, and glycaric acids (sugar dicarboxylic acids, aldaric acids) (Fig. 36). Aldonic acids easily cyclize to the corresponding y-lactones. Glycaric acids may form dilactones. 

Aldose-derived carboxylic acids are synthesized in microorganisms, plants, and animals. The uronic acids are most widespread. 

Pyridine nucleotide-dependent dehydrogenases (C 2.1) transform aldose derivatives to uronic acids, e.g., UDP-D-glucose to UDP-D-glucuronic acid and in animals also to aldonic acids, e.g., D-glucose-6-phosphate to D-gluconic acid-6-phos-phate (glucose-6-phosphate dehydrogenase). 

Heterosidic uronides are frequently built in animals from nucleotide diphosphate uronic acids. Formation of uronides increases water solubility and is a prerequisite for the excretion of many secondary products and other compounds (E 1). 

Because C-6 of glucuronic acid becomes C-1 of gulonic acid, numbering of the C-atoms of L-ascorbic acid is reverse to that of glucuronic acid 

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For quite sparingly soluble substances, formic acid, pyridine, bromobenzene, nitrobenzene, and occasionally also phenol, ethyl benzoate, aniline, and dioxan are used. A distinct relation exists between the constitution of solute and solvent, and is expressed by the old rule similia similibus solvuntur. Thus, as is well known, substances containing hydroxyl (e.g. sugars, carboxylic acids) are soluble in water, whereas hydrocarbons are more soluble in benzene and petrol ether than, for example, in alcohols. 

CARBAZONES, see CARBAZIDES CARBOHYDRATES and SUGARS CARBOXYLIC ACIDS, see ACIDS, CARBOXYLIC CATALYTIC HYDROGEN-ION REDUCTION DEUTERATED COMPOUNDS, see ISOTOPES D IAZ0 COMPOUNDS DIAZONIUM SALTS ESTERS, CARBOXYLIC... 

Flavor enhancers are used imiversally in the food and pharmaceutical industries. Sugar, carboxylic acids (e.g., citric, malic, and tartaric), common salt (NaCl), amino acids, some amino acid derivatives (e.g., monosodium glutamate—MSG), and spices (e.g., peppers) are most often employed. Although extremely effective with proteins and vegetables, MSG has limited use in pharmaceuticals because it is not a sweetener. Citric acid is most frequently used to enhance taste performance of both liquid and solid pharmaceutical products, as well as a variety of foods. Other acidic agents, such as malic and tartaric acids, are also used for flavor enhancement. In oral liquids, these acids contribute unique and complex organoleptic effects, increasing overall flavor quality. Common salt provides similar effects at its taste threshold level in liquid pharmaceuticals. Vanilla, for example, has a delicate bland flavor, which is effectively enhanced by salt. 

The main reaction products of prebiotic chemistry were H2, H20, CH4, CO, C02, NH3, and N2. These compounds formed many intermediates including ions and radicals. The more important molecules that formed were formaldehyde HCHO, hydrogen cyanide HCN, phosphate ions, and cyan amide NH2CN. The final spectrum of products encompassed glycerol, glyceraldehyde - the parent compounds of sugars - carboxylic acids, amino acids, urea, guanidine, purines, and pyrimidines. As an example for the many possible interactions the formation of the nucleobase, uracil is shown in Fig. 2.1. 

Molnar-Perl I (2000) Role of chromatography in the analysis of sugars, carboxylic acids and amino acids in food. Journal of Chromatography A 891 1-32. 

Simple Sugars—Secondary Metabolites Nomenclature 2-Deoxyhexoses 6-Deoxyhexoses Methoxy Sugars Branched-Chain Sugars Sugar Carboxylic Acids Amino Sugars... 

The simple sugars are either polyhydroxy aldehydes or polyhydroxy ketones. The carbohydrates ordinarily also encompass all substances that are closely related to sugars, e.g., simple derivatives (amino sugars, carboxylic acids, etc.) and polymers of them (oligo- and polysaccharides), which will be discussed in Chapt. XVII. 

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