Carbohydrates complexes with iron

The parenteral use of complexes of iron and carbohydrates has resulted in anaphylactic-type reactions. Deaths associated with such administration have been reported therefore, use iron dextran injection only in those patients in whom the indications have been clearly established and laboratory investigations confirm an iron-deficient state not amenable to oral iron therapy. Because fatal anaphylactic reactions have been reported after administration of iron dextran injection, administer the drug only when resuscitation techniques and treatment of anaphylactic and anaphylactoid shock are readily available. 

The challenge with parenteral iron therapy is that parenteral administration of inorganic free ferric iron produces serious dose-dependent toxicity, which severely limits the dose of that can be administered. However, when the ferric iron is formulated as a colloid containing particles with a core of iron oxyhydroxide surrounded by a core of carbohydrate, bioactive iron is released slowly from the stable colloid particles. In the USA, the three available forms of parenteral iron are iron dextran, sodium ferric gluconate complex, and iron sucrose. 

The food fiavorist also must be aware of metal complexes, which carbohydrates are capable of forming, Iron salts not only form complexes with dietary fiber, but with nearly all of the known natural sugars. Fructose, maltitol. sorbitol, and xylitol can easily form complexes with the ferric... 

One of these approaches is the formation of polysaccharide iron complexes (PIC), such as Niferex, a compound used in the treatment of iron deficiency anemia. PICs are formed by neutralization of FeCb-containing carbohydrate solutions with base. Mineral particles of roughly the same size as ferritin cores can be made. These contain iron in an octahedral enviromnent coordinated to oxygen. However, the long-range order of the polynuclear iron core is closer to that of akaganeite rather than ferrihydrite. ... 

HP-NAP is to date the only H. pylori carbohydrate binding protein that has been subjected to structural studies, although not in complex with carbohydrates. The neutrophil-activating protein forms a dodecameric structure arranged in a nearly spherical shell with a central iron-containing cavity [47], The structure of HP-NAP has similarities to dodecameric bacterial ferritins (Dps-like family). However, unlike the Dps proteins, a large number of positively charged residues are found on the surface of HP-NAP. 

Comparison of the complex-formation constants for bofli 1 1 (57 and 58) and 1 2 (such as 59) species ° with those obtained for the respective copper(II) complexes with parent amino acids revealed that the fructosyl moiety provides for an additional chelate effect in D-fructose-a-amino acids and as a consequence, a significant increase in the complex stability. In the absence of an anchoring chelating group, such as a-carboxylate, the D-finctosamine structure is not a good copper(II) chelator, and Cu(n) expectably does not form stable complexes with the carbohydrate in A -d-Iructose-L-lysine peptides. Although it would be expected that iron(III) complexes with D-finctose-amino acids in aqueous solutions, no related thermodynamic equilibrium studies have been done so far for this important redox-active metal. 

Autoxidation of D-fructosamine residues in glycated polylysine in the presence of iron(III) can be promoted by sunlight, as shown by monitoring formation of the main oxidation product, A -carboxymethyl-L-lysine (CML, 65). The proposed oxidation mechanism includes 2,3-enolization of the carbohydrate and formation of the enolate complex with Fe (Scheme 34). Ferricyanide anion, Fe(CN)6, is readily reduced by D-fructosamines and has traditionally been employed as a selective indicator for Amadori compounds in the presence of parent o-glucose or lactose,... 

Rapeseed meals frequently contain tannins. These are polyphenolic compounds that complex with proteins and carbohydrates to form enzyme-resistant substrates with a consequent lowering of digestibility. This may also result from the combination of the tannins with digestive enzymes, with a consequent loss of activity. Tannins may cause damage to the intestinal mucosa and are known to interfere with iron absorption. 

Iron salts are easily accessible, inexpensive and abundant and the metal itself is non-toxic. Their use should therefore become attractive from an economic and environmental point of view in a wide variety of carbohydrate transformations, in either stoichiometric applications or as a catalyst. As stated in the introduction, this review concentrates on a few transformations promoted by ferric salts used as Lewis acids in our laboratories and does not present exhaustive work done in carbohydrate chemistry with these salts. Many more other applications have been reported. However, their uses could be far more developed for fast and selective transformations of carbohydrates to useful new molecular constructs. Besides the acidic properties of iron(iii) presented here, iron chemistry is rich and could be particularly fruitful with carbohydrates in generating new types of complexes for regioselective transformations or in carbon-carbon forming reactions based on iron-catalyzed cross-coupling reactions. The glycochemistry community should certainly expect many more useful accomplishments in the near future. 

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