Enhancement of antioxidant and anti-inflammatory activities of bioflavonoid rutin by complexation with transition metals
Introduction
1The harmful intervention of free radicals in normal metabolic processes leading to pathologic changes is a consequence of their interaction with various biological compounds inside and outside cells. To protect biomolecules against the attack of free radicals and/or to suppress the resultant damage, numerous natural and synthetic free radical scavengers and antioxidants have been developed and studied. Among them, flavonoids, natural polyphenolic compounds, have attracted significant interest [1]. Actually, the beneficial clinical and curative effects of flavonoids in the treatment of virus infection, inflammation, diabetes mellitus, headache, etc. in humans have long been shown, but they are “to a large extent based on empirism since this praxis is much older than the science of chemistry” [2]. However, at present, many studies show the importance of the antiradical activity of flavonoids. Thus, it has been shown that flavonoids are the effective inhibitors of lipid peroxidation, oxygen radical overproduction by inflammatory cells, free radical-mediated cytotoxicity, and chromosome damage [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16].
For several years we have studied the antioxidant activity of rutin, a non-toxic flavonoid glycoside with P vitamin activity, and found that this flavonoid is able to suppress various free radical-mediated processes such as in vitro lipid peroxidation [6], [14], the mutagenic effect of asbestos fibers on human lymphocytes [9], and the overproduction of free radicals in iron-overloaded rats [16]. We showed that rutin may be successfully applied for the treatment of patients with Fanconi anemia and β-thalassemia (congenital diseases associated with oxygen radical overproduction) [17], [18], [19]. Antioxidant effects of rutin were also shown by other authors. Thus, Negre-Salvayre et al. [8] found that rutin potentiated the antilipoperoxidative capacity of α-tocopherol and ascorbic acid. Grinberg et al. [20] showed that rutin suppressed oxygen radical overproduction in thalassemic erythrocytes.
Although the above data show the efficiency of rutin as an antioxidant and free radical scavenger and suggest the clinical relevance of rutin in the management of “free radical” pathologies, this compound is not the most active antioxidative flavonoid, especially in comparison with flavonoid aglycones such as quercetin or kamferol [1]. Unfortunately, the use of aglycones as pharmaceutical agents is restricted due to their mutagenic and cytotoxic activity [1]. Therefore, it is desirable to develop a method to enhance the antioxidant and free radical-scavenging potential of non-toxic flavonoids such as rutin without radically altering their structure. We suggested that this can be achieved by the preparation of transition metal–rutin complexes, in which the flavonoid molecule acquires an additional superoxide-dismuting center without the formation of new covalent bonds.
In the present work, the antioxidant and free radical-scavenging properties of two iron– and copper–rutin complexes were studied. Furthermore, the inhibitory effects of these complexes on lung inflammation and interstitial fibrosis in rats induced by anticancer antibiotic bleomycin were investigated. It was found that the iron– and copper–rutin complexes manifested enhanced antioxidant activities and significantly suppressed inflammation and lung edema in BLM-treated rats.
Section snippets
Chemicals
Rutin, bleomycin, xanthine, cytochrome c, TBA, the chemiluminescent probes luminol and lucigenin, the media HBSS and minimal essential medium (MEM), and the enzymes bovine erythrocyte CuZnSOD (copper, zinc superoxide dismutase, EC 1.15.1.1) and xanthine oxidase (EC 1.1.3.22) were purchased from Sigma Chemical Co. The other salts, solvents, and acids were of the greatest available chemical purity.
Preparation of metal–rutin complexes
The metal–rutin complexes Fe(rut)Cl3 and Cu(rut)Cl2 were prepared by mixing rutin with iron or
Effects of iron ions, copper ions, and rutin and metal–rutin complexes on oxygen radical production by rat peritoneal macrophages
Ferric ions sharply enhanced spontaneous luminol-amplified CL produced by rat peritoneal macrophages in the presence and absence of BLM and had no effect on zymosan-stimulated CL (Fig. 2). The effect of ferric ions on lucigenin-amplified CL was more complicated (Fig. 3), while cupric ions were always inhibitory (Fig. 4). Rutin inhibited all kinds of luminol- and lucigenin-amplified CL by macrophages. Cu(rut)Cl2 was a much more efficient inhibitor (by 2–30 times) of oxygen radical production
Discussion
As mentioned above, a main goal of this work was to study the antiradical, antioxidant activity of iron and copper complexes of rutin, which acquire additional superoxide-dismuting centers and thereby may be more effective free radical scavengers compared to the parent rutin. We have already shown [25], [26] that the transition metal complexes of rutin are indeed the effective scavengers of active free radicals produced by xanthine oxidase or are formed during lipid peroxidation of liposomes
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