Carbohydrate derivatives vitamins

The antiscorbutic factor of fresh fruits, which prevents the development of the typical symptoms of scurvy in humans, is a carbohydrate derivative known as vitamin C or ascorbic acid. This substance is not a carboxylic acid, but a lactone, and owes its acidic properties (and ease of oxidation) to the presence of an enediol grouping. It belongs to the l series by the glyceraldehyde convention ... 

Small molecules The term small molecule refers to a diverse range of substances including lipids and derivatives vitamins hormones and neurotransmitters and carbohydrates. 

Several investigators have reported that ascorbic acid can be analyzed by gas-liquid chromatography following conversion of the parent compound to its trimethylsilyl ether (61-66). The procedures have been found to be reliable and to produce results comparable with those obtained by colorimetric procedures. In most cases, however, measurement of only the reduced form of the vitamin is possible (67). One method is suitable for microanalytical work and has the advantage that several other carbohydrates and carbohydrate derivatives can be measured simultaneously in the same extract (67). 

Celluloses Amines, amino acids, antibiotics, carbohydrates, glycosides, hydrocarbons, inorganic ions, nucleic acids, organic acids, peptides, urea derivatives, vitamins... 

Contents B. FRASER-REID and R. C. ANDERSON, Carbohydrate Derivatives in the Asymmetric Synthesis of Natural Products — H. JONES and G. H. RASMUSSON, Recent Advances in the Biology and Chemistry of Vitamin D — S. LIAAEN-JENSEN, Stereochemistry of Naturally Occurring Carotenoids — T. KASAI and P. O. LARSEN, Chemistry and Biochemistry of y -Glutamyl Derivatives from Plants Including Mushrooms (Basidiomycetes) - Author Index - Subject Index. 

Nutrient analysis of stabilized rice bran and its derivatives indicates that it is a good source of protein, dietary fiber and carbohydrates, in addition to several valuable phytonutrients, antioxidants, vitamins and minerals (Table 17.1). SRB and its water-soluble and water-insoluble derivatives contain all the nutrients at different levels. They are gluten and lactose free and do not give rise to any food allergy. 

Fatty add synthase is a large multienzyme complex in the cytoplasm that is rapidly induced in the liver after a meal by high carbohydrate and the concomitant rise in insulin levels. It contains an acyl carrier protein (AGP) that requires the vitamin pantothenic add. Althoi malonyl CoA is the substrate used by fetty acid synthase, only the carbons from the acetyl CoA portion are actually incorporated into the fatty acid produced. Therefore, the fetty add is derived entirely from acetyl CoA. 

Vitamin C, also known as L-ascorbic acid, clearly appears to be of carbohydrate nature. Its most obvious functional group is the lactone ring system, and, although termed ascorbic acid, it is certainly not a carboxylic acid. Nevertheless, it shows acidic properties, since it is an enol, in fact an enediol. It is easy to predict which enol hydroxyl group is going to ionize more readily. It must be the one P to the carbonyl, ionization of which produces a conjugate base that is nicely resonance stabilized (see Section 4.3.5). Indeed, note that these resonance forms correspond to those of an enolate anion derived from a 1,3-dicarbonyl compound (see Section 10.1). Ionization of the a-hydroxyl provides less favourable resonance, and the remaining hydroxyls are typical non-acidic alcohols (see Section 4.3.3). Thus, the of vitamin C is 4.0, and is comparable to that of a carboxylic acid. 

Vitamin Bj (8.44, riboflavin) is a benzopteridine derivative carrying a ribityl (reduced ribose) side chain. It occurs in almost all foods, the largest amounts being found in eggs, meat, spinach, liver, yeast, and milk. Riboflavin is one of the major electron carriers as a component of flavine-adenine dinucleotide (FAD), which is involved in carbohydrate and fatty acid metabolism. A hydride ion and a proton are added to the pyrazine ring of... 

Clinical Chemistry (see Chapter 10). Gas chromatography is adaptable to such samples as blood, urine, and/or biological fluids. Compounds such as proteins, carbohydrates, amino acids, fatty acids, steroids, triglycerides, vitamins, and barbiturates are handled by this technique, directly or after preparation of appropriate volatile derivatives. 

Functionalised carbenes can anchor free carbenes to the metal site, introduce hemilabil-ity, provide a means to immobilise transition metal carbene catalysts, introduce chirality, provide a chelate ligand or bridge two metal centres. NHC can be attached to carbohydrates and camphor, derived from amino acids and purines, and they can be used as organocata-lysts mimicking vitamin B1 or as weak solvent donors in lanthanide chemistry. There are many possibilities which are still only scarcely explored. 

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