Dismutation activity

In 1989, we showed [142] that the Fe2+(rutin)2 complex is a more effective inhibitor than rutin of asbestos-induced erythrocyte hemolysis and asbestos-stimulated oxygen radical production by rat peritoneal macrophages. Later on, to evaluate the mechanisms of antioxidant activities of iron rutin and copper-rutin complexes, we compared the effects of these complexes on iron-dependent liposomal and microsomal lipid peroxidation [165], It was found that the iron rutin complex was by two to three times a more efficient inhibitor of liposomal peroxidation than the copper-rutin complex, while the opposite tendency was observed in NADPH-dependent microsomal peroxidation. On the other hand, the copper rutin complex was much more effective than the iron rutin complex in the suppression of microsomal superoxide production, indicating that the copper rutin complex indeed acquired additional SOD-dismuting activity because superoxide is an initiator of NADPH-dependent... 

Superoxide-dismuting activity of copper rutin complex was confirmed by comparison of the inhibitory effects of this complex and rutin on superoxide production by xanthine oxidase and microsomes (measured via cytochrome c reduction and by lucigenin-amplified CL, respectively) with their effects on microsomal lipid peroxidation [166]. An excellent correlation between the inhibitory effects of both compounds on superoxide production and the formation of TBAR products was found, but at the same time the effect of copper rutin complex was five to nine times higher due to its additional superoxide dismuting capacity. 

The inhibition of lipid peroxidation by metalloporphyrins apparently depends on metal ions because only compounds with transition metals were efficient inhibitors. Therefore, the most probable mechanism of inhibitory effects of metalloporphyrins should be their disuniting activity. Manganese metalloporphyrins seem to be more effective inhibitors than Trolox (/5o = 204 pmol I 1) and rutin (/50 112 pmol I 1), and practically equal to SOD (/50= 15 pmol I 1). The mechanism of inhibitory activity of manganese and zinc metalloporphyrins might be compared with that of copper- and iron-flavonoid complexes [167,168], which exhibited enhanced antiradical properties due to additional superoxide-dismuting activity. 

The mechanisms of superoxide-dismuting activity of SODs are well established. Dismutation of superoxide occurs at copper, manganese, or iron centers of SOD isoenzymes CuZnSOD, MnSOD, or FeSOD. These isoenzymes were isolated from a variety of sources, including humans, animals, microbes, etc. In the case of CuZnSOD, dismutation process consists of two stages the one-electron transfer oxidation of superoxide by cupric form (Reaction (1)) and the one-electron reduction of superoxide by cuprous form (Reaction (2)). 

Effect of method of preparation on the dismutation activity of CCI2F2 over Cr203-Mg0-Al203 catalysts... 

Recently, Kemnitz et al [14] have shown the influence of Mg " and Cr " additions into AIF3 lattice separately on its structure and dismutation activity of CCI2F2 In the present investigation the effect of Mg " addition to Cr203-Al203 catalysts on their dismutation activity, acid site distribution and coke formation has been studied in detail. 

The fresh and used catalysts were characterised by BET-SA, XRD, ESR, coke content and TPD of ammonia and evaluated by the dismutation activity of CCI2F2 at various temperatures ranging from 275-450°C. An all glass high vacuum unit (lO" torr) was used for the measurement of BET surface area. The XRD patterns were recorded on the Phillips PW 1051 diffractometer using Ni-filtered Cu-Ka radiation. ESR spectra were recorded at room temperature on a Bruker ER 200D-SRC X-band spectrometer with 100 kHz modulation. The carbon content of the catalysts were determined on a Perkin-Elmer 240-B microanalyser. 

Y. Ilan, J. Rabani, I. Fridovich, and R.F. Pasternack, Superoxide Dismuting Activity of An Iron Porphyrin, Inorg. Nucl. Chem. Lett., 17 (1981) 93. 

The dismutating activity of bound manganese (10) may also be important. The generation of hydrogen peroxide in this reaction may be tolerated by the presence of additional enzyme systems that catalyse the destruction of H2O2 (11) (i) ascorbate peroxidase, (ii) dehydroascorbate reductase, and (iii) glutathione reductase. 

However, some oxides, such as supported Re207 (at 50-120°) or molybdenum oxide (at higher temperatures), show dismutation activity without alkyl treatment. Presumably, partial reduction of the surface by olefin exposes suitably liganded (M—O—M=CR2) centres. Further reduction (slow anion migration to the surface) leads to deactivation, but activity is restored by reoxidation. 

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