Fenton reaction and

Gutteridge, J.M.C. (1986). Iron promoters of the Fenton reaction and lipid peroxidation can be released from haemoglobin by peroxides. FEBS Lett. 201, 291-298. 

For a long time one question remained unanswered the efficiency of the Fenton reaction as the in vivo producer of hydroxyl radicals due to the low rate of Reaction (2) (the rate constant is equal to 42.11 mol 1 s 1 [18]). It is known that under in vitro conditions the rate of Fenton reaction can be sharply enhanced by chelators such as EDTA, but for a long time no effective in vivo chelators have been found. From this point of view new findings obtained by Chen and Schopfer [19] who found that peroxidases catalyze hydroxyl radical formation in plants deserve consideration. These authors showed that horseradish peroxidase (HRP) compound III is a catalyst of the Fenton reaction and that this compound is one to two orders of magnitude more active than Fe EDTA. 

Rodenas et al. [77] studied PMN-stimulated lipid peroxidation of arachidonic acid. As MDA formation was inhibited both with L-arginine (supposedly due to the formation of excess NO) and DTPA (an iron ion chelator), it was concluded that about 40% of peroxidation was initiated by hydroxyl radicals formed via the Fenton reaction and about 60% was mediated by peroxynitrite. However, it should be noted that the probability of hydroxyl radical-initiated lipid peroxidation is very small (see above). Phagocyte-mediated LDL oxidation is considered below. 

The radical or nonradical chemistry of the Fenton-like systems, including the Fenton reaction and the Fe(III)—ROOH (or H2O2) system, is still hotly debated.1123,1130-1134 New information supporting a free-radical mechanism with carbon- and oxygen-centered radicals1135-1138 and new evidence for a nonradical process1139,1140 have been published. 

Manevich Y, Held KD, Biaglow JE (1997) Coumarin-3-carboxylic acid as a detector for hydroxyl radicals generated chemically and by gamma radiation. Radiat Res 148 580-591 Maples KR, Johnson NF (1992) Fiber-induced hydroxyl radical formation correlation with mesothelioma induction on rats and humans. Carcinogenesis 13 2035-2039 MarkG, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Maskos Z, Rush JD, Koppenol WH (1990) The hydroxylation of the salicylate anion by a Fenton reaction and v-radiolysis a consideration of the respective mechanisms. Free Rad Biol Med 8 153-162... 

One of the most important sugar lesion is the 3 -phosphoglycolate that is typically formed in the presence of O2 (for its excision by purified HeLa cell extracts see Winters et al. 1992). Specifically deuterated nucleoside triphosphates were used for incorporation into dsDNA by PCR (Balasubramanian et al. 1998). Hydroxyl radicals were generated by a Fenton reaction, and the yields of free 3 -phosphate end groups, 3 -phosphoglycolate and 5 -aldehyde were measured. Depending on the position of the deuteration, the yields vary with respect to a non-deuterated sample (Table 12.9). 

Fluvastatin (Fig. 21) is a member of the drug class of statins used to treat hypercholesterolemia and to prevent cardiovascular disease. It is able to decrease ROS, such as hydroxyl radicals and superoxide anions generated by the Fenton reaction, and by the xanthine-xanthine oxidase system. The an-tioxidative effect of fluvastatin was thought to have caused not only the scav-... 

The Photo-Fenton Reaction and Other Iron-Based Photoprocesses. 346... 

ROS produced by sugars and glycated protein autoxidation participate in oxidizing of already glycated proteins and affect other proteins (H24). These reactions are catalyzed by metal ions (W17). The presence of metal ions may, moreover, initiate the Fenton reaction and produce hydroxyl radicals. A carbon-centered 1-hydroxyalkyl radical was found during autoxidation of glyceraldehyde (T12). 

Note that in the C204 reactant, C is in the +3 oxidation state, whereas in the C20 product it is +7/2. Thus, it underwent oxidation in order to reduce Fe(III) to Fe(II). This Fe(II) can (in the presence of H202) generate the potent OH radicals. This is called the Fenton reaction, and when the Fe(II) is produced by the photolytic reduction of Fe(III), it is called a photo-Fenton reaction (see Section 10.1.1.2). 

As mentioned, DNA could be cleaved with the Fenton reagent, and then we can take into consideration whether the qinghaosu-ferrous ion could also cleave DNA, although there are two different kinds of free radicals the oxygen radical from the Fenton reaction and the carbon free radical from the reaction of the qinghaosu-ferrous ion. It is makes sense that the malaria parasite is mainly living in the red blood cell however, the mature red blood cell has no nucleus, but the... 

In terms of potential chemical interactions, the effects of NO on ROS-induced injury are multiple, and some effects can be classified as prooxidant and others may be classified as antioxidant still others can be classified as both. In terms of the metal-catalyzed Haber-Weiss reaction, there are two primary effects of -NO. The binding of NO to metal ions will prevent the Fenton reaction and thus results in an antioxidant action. Another important antioxidant action of NO (and its oxidized product N02) is its reaction with hpid radicals, thus resulting in radical chain termination. ... 

The reaction of Cud) with H2O2 generating OH radicals (Eq. 44) resembles that of the iron(II) complexes (Eq. (27), Fenton reaction) and although it is followed by a fast opposite reaction (Eq. 45) that consmnes the radicals, copper can contribute to the oxidative degradation in the Fenton-type processes (205,232-235). On the other hand, the photophysical properties of copper(I) bis(phenanthroline) complexes induced by a MLCT excitation were interpreted as formation of the Cu(I) Cu(II) excited state (236). 

However, because of the small rate constant of the above Fenton reaction (<10 M sec ), the oxidation of Fe by 02 [Eq. (40)] may completely overshadow the Fenton reaction and may have a significant role because of its much higher rate constant ( 10 M sec ). 

It was noted qualitatively that the Rf values of the products of the Fenton Reagent (H202 + Fe2+) reaction with RNO and the radiolysis products of acid RNO solutions were essentially the same. The spectral maxima of the extracted bands from the TLC plates of separated Fenton reaction and radiolysis products were also similar and many of these products absorb strongly in the 400-440 n.m. region of the spectrum but have minima around 350 n.m. Again it was difficult to distinguish between primary and secondary products. 

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