Iron chelating ability

Morel et al. (1993) have reported that three flavanoids (catechin, quercetin and diosmetin) are cytoprotective on iron-loaded hepatocyte cultures. Their cytoprotective activity (catechin > quercetin > diosmetin) correlated with their iron-chelating ability (Morel et al., 1993). These compounds should also be good phenolic antioxidants so iron chelation may only be part of the story. 

Ihnat and coworkers substituted the primary amine group with a series of gradually increasing alkyl amides 113-119, aromatic amides 120 and 121, succinamide 122 and methylsulfonamide 123 with a systematic increase in partition coefficient (octanoFwater), to increase permeability while retaining iron-chelating ability. The formamide derivative... 

Scholnick, F. and Pfeffer, P. E. 1980. Iron chelating ability of gluconamides and lactobio-namides. J. Dairy Sci. 63, 471-473. 

The iron chelating ability of DFB is due to the hydroxamic acid, a functional group that possesses a natural affinity for iron(III). Also inherent in this structure is a powerful chelate effect due to the 9 atom spacing between hydroxamic acid groups, tdiich permits three neighboring hydroxamic acids to fit the octahedral coordination sphere of the iron(III) without severe steric strain. 

Afanas ev et al. demonstrated the ability of rutin to form a stable complex with Fe2+ at physiological pH [142]. The absorption spectrum of the Fe2+-rutin complex did not change during 8 hours [142]. Morel et al. investigated radiochemically the capacity of three flavonoids (catechin, quercetin and diosmetin) and desferrioxamine - a powerful chelator of Fe3+ - to remove Fe3+ from iron-loaded hepatocytes [18, 143]. Nitrilotriacetic acid - a low affinity iron-chelator - was used to maintain Fe3+ in a soluble state. The iron-chelating ability decreased in the following order desferrioxamine > catechin > quercetin > diosmetin (which had a very low activity) [18, 143]. 

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-... 

The question then arises whether the formation of ROS can indeed be causally related to cell death or whether it simply constitutes an epiphenomenon. The strongest evidence for a causal relationship comes from studies that demonstrate the ability of iron chelators and antioxidants to protect against aminoglycoside-induced ototoxicity. Effective protectants include chelators such as deferoxamine and dihydroxybenzoic acid and a variety of other antioxidant molecules includ-... 

The Asc - signal has also been monitored to investigate the ability of iron chelators to prevent OH formation 264 the interactions between dental... 

Flavonoids have the ability to act as antioxidants by a free radical scavenging mechanism with the formation of less reactive flavonoid phenoxyl radicals [Eq. (1) and (2)]. On the other hand, through then-known chelating ability these compounds may inactivate transition metals ions (iron, copper), thereby suppressing the superoxide-driven Fenton Reaction, Eqs. (3) and (4), which is currently believed to be the most important route to activate oxygen species [51]. 

Iron is a nonamphoteric, transition element with the ability to exist in two oxidation states—Fe2+ (ferrous) and Fe3+ (ferric). A positive reaction to alkaline ferric chloride is an indication of the presence of hydroxyl groups with which Fe2+ forms colored complexes. Stable copper and iron chelates... 

In analytical chemistry 2,2 -bipyridyl and its derivatives have many applications they form bidentate chelating agents with metal ions, amongst them iron, ruthenium, copper, and platinum. However, a 6-substituent decreases the chelating ability of 2,2 -bipyridyl by a steric interaction, while 6,6 -disubstitution totally inhibits it. 

A key property for an oral iron chelator is its ability to cross biological membranes enabling it to be absorbed from this intestinal tract. The above property however will also endow the molecule the ability to efficiently penetrate the blood-brain barrier. For this reason, it is important to ensure that chelating agents are directed to target tissue such as the heart and liver whilst minimising exposure to critical organs/cells. 

More recently, the notion that the beneficial effects of iron-chelating agents are simply due to chelation of the metal ion has been challenged [64]. This is due to the demonstrated ability of the commonly used hydroxamate iron chelator desferrioxamine to act as a superoxide and hydroxyl-radical scavenger [65]. The relatively stable desferrioxamine nitroxide free radical (T1/2 10 min)... 

A wide range of iron chelators have been shown to inhibit ribonucleotide reductase [79,80] and this is undoubtedly the reason for cytotoxic properties of many such molecules. Some iron chelators may also function as free radical scavengers, for instance, hydroxyurea which inhibits the enzyme by the latter mode of action. Such agents hold the cell cycle in the S-stage because the synthesis of DNA is inhibited. The ability of iron chelators to inhibit ribonucleotide reductase has led to several proposals for therapeutic application. 

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