Useful Iron Chelators

A molecule that binds iron through coordinating moieties (e.g., carboxylates or amines). They are used to inhibit iron-catalyzed free radical reactions or to treat iron overload conditions. Desferrioxamine and defer-iprone are two widely used iron chelators. 

Figure 25.24 Removal of H2S by partial oxidation of H2S using iron chelate.

The stability of metal complex is also given by the number of chelate rings formed in the resultant ligand-metal complex. For example, desfer-rioxamine, the most widely used iron chelator, minimizes OH production by acting as a hexadentate ligand [Liu and Hider, 2002]. Unfortunately, there is not enough information on the denticity of polyphenols as metal chelators to assess the relevance of the stability of the flavonoid-metal complex formed. 

In isolated rat nuclei, SOD inhibits bleomycin-induced membrane peroxidation, but has no effect on bleomycin-catalysed DNA scission [57]. Thus, it may be possible to use iron chelators to reduce the toxic extracellular side effects of these drugs, whilst leaving the intracellular therapeutic mode of action unaltered. In fact, it has been demonstrated that the cardiotoxicity of adriamycin can be inhibited by the chelating agent ICRF-187 [60],... 

The identification of rhodotorulic acid as a potentially useful iron-chelating drug. Blood 1974, 44, 911. 

For example, a number of potentially useful iron-chelating drugs are derivatives of phenols, carboxylic acids, and amines. Carboxylic acids, being a metabolic end product, are stable to microsomal oxidation but are subject to conjugation. Phenols are similarly subject to conjugation and also to microsomal hydroxyla-tlon. Amines are subject to conjugation (if primary or secondary), and to oxidation and N-dealkylation. 

Jeffrey, G. C., Cooper, L. A., and Whipple, S. S. (1988) Downhole Hydrogen Sulfide Scavenging in Drilling Mud Using Iron Chelates, US Patent 4756836, pp. 1-4. 

Hider RC, Porter JB, Singh S (1994) The design of therapeutically useful iron chelators. In Bergeron RJ, Brittenham GM (eds) The development of iron chelators for clinical use. CRC Press, Boca Raton, pp 353-371 Hoffbrand AV, Ganeshaguru K, Hooton JWL, Tattersall MHN (1976) Effect of iron deficiency and desferrioxamine on DNA synthesis in human cells. Br J Haematol 33 517-526... 

Solutions of iron chelates can be used to remove hydrogen sulfide and oxides of sulfur and nitrogen in industrial gas scmbbing processes (41,50,51) before flue gases are released to the atmosphere. 

Another compound, the antimicrobial action of which is associated with chelation, is 2-pyridinethiol-A/-oxide [3811-73-2] (Omadine). Activity has been shown to depend on coordinating property. The iron chelate is active, but not the free pyridine compound (200). In the form of its zinc chelate it is found in shampoos to control seborrheic dermatitis (201). Other appHcations of this useful chemical include preservation of adhesives, plastics, latex paints, polyurethane foam, and metal working fluids (202). 

The experimental results imply that the main reaction (eq. 1) is an equilibrium reaction and first order in nitrogen monoxide and iron chelate. The equilibrium constants at various temperatures were determined by modeling the experimental NO absorption profile using the penetration theory for mass transfer. Parameter estimation using well established numerical methods (Newton-Raphson) allowed detrxmination of the equilibrium constant (Fig. 1) as well as the ratio of the diffusion coefficients of Fe"(EDTA) andNO[3]. 

The oxidation reaction (eq. 2) is an irreversible reaction with first order in oxygen and smmd ordo in iron chelate. The kinetic constants at various temperatures were determined using a penetration theory based expression derived by De Coursey [4] and the results are presented in Fig. 2. 

Iron-chelating agents 4.5 Use of microbial enzymes in sterility... 

Experimental in vitro investigations utilizing liposomal-encapsulated and polyethylene glycol-conjugated SOD and catalase have demonstrated the potential value of such means in countering oxidative asbestos-related diseases (Freeman etal., 1985 Mossman etal., 1986). In addition to using supplementary endogenous antioxidant enzymes, the use of iron chelators like desferrioxamine... 

Depending on the ability of specific transport systems to utilize the predominant metal chelates present in the soil solution, competition may occur between plants and microorganisms and between different types of microorganisms for available iron. This has been particularly well studied for Pseudomonas sp., which produce highly unique iron chelators that are utilized in a strain specific manner but which also retain the ability to use more generic siderophores pro-... 

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