Flavonoids antioxidant action

L. Anila and N.R. Vijayalakshmi, Antioxidant action of flavonoids from Mangifera indica and Emblicas officinalis in hypercholesterolemic rats. Food Chem. 83 (2003) 569-574. 

C) The antioxidant actions of flavonoids appear to participate in their antithrombotic action. Flavonoids bind to platelet membranes and scavenge platelet-generated lipid peroxides and free radicals, restoring the biosynthesis and the action of endothelial prostacyclin and nitric oxide (NO), respectively [49,88]. 

Fig. 2. Schematic diagram delineating some of the multiple stages of mutagenesis and the interference by flavonoids. 1. Flavonoids induce apoptosis and enhance mutagen detoxification and extrusion from the cell. 2. Flavonoids interfere with the metabolic activation of mutagens and protect DNA by means of their antioxidative action. GST glutathione-S-transferase ROM reactive oxygen metabolites.

The reactions between free radicals and flavonoids (or polyphenols) are assumed to form aroxyl radicals (PO) (reaction 8). The stability of these secondary radical species is an important element to be considered in their antioxidant actions. Flavonoids with similar reduction potentials can originate radicals with very different reactivity toward other molecules present in biological systems. While a stable and relatively nonreactive PO is also nonreactive to propagate the chain reaction, a high reactive PO would propagate rather than interrupt a chain reaction. 

Galleano, M. Verstraeten, S.V. Oteiza, P.L Fraga, C.G. 2010. Antioxidant actions of flavonoids Thermodynamic and kinetic analysis. Arch. Biochem. Biophys. 501 23-30. 

While the positive health benefits associated with the consumption of a flavonoid-rich diet cannot be attributed to any one factor, the antioxidant properties of certain flavonoids have been the focus of considerable attention [8]. The antioxidant actions of chocolate flavonoids were first studied inhibiting LDL-oxidation [9,10]. As a consequence of the availability of purified procyanidins from cocoa (dimer-decamer), this particular family of... 

Letan [175] proposed a series of structural requirements that flavonoids had to fulfil in order to have antioxidative action ... 

Extracts derived from most members of the Labiatae family (Table 3) have the potential to reduce the oxidation of food products and extend shelf life. This antioxidant action is dependent on the ability of the constituent phenolics to scavenge free radicals and chelate metals [27]. This dual effect has implications for CHD since it has been proposed in some studies, mainly from Europe, that a high status of iron increases the risk of CHD [28]. A number of the active compounds found in rosemary have also been found in sage and other herbs. In oregano, four flavonoids were identified among the active fraction [29], while in thyme, dimers of thymol and flavonoids have been isolated and characterized. 

The antioxidant actions of flavonoids appear to be involved in their observed antithrombotic action [50-52]. The antithrombotic and vasoprotective actions of quercetin, rutin, and other flavonoids have been attributed to their ability to bind to platelet membranes and scavenge free radicals [50]. In this manner, flavonoids restore the biosynthesis and action of endothelial prostacyclin and endothelialderived relaxing factor (EDRF), both of which are known to be inhibited by free radicals [50, 53, 54]. However, some flavonoids may inhibit arachidonic acid metabolism and platelet function by flavonoid-enzyme interactions rather than by antioxidant effects [55]. In addition to their antiaggregatory effects, flavonoids appear to increase vasodilation by inducing vascular smooth muscle relaxation, which may be mediated by inhibition of protein kinase C, PDFs, or by decreased cellular uptake of calcium [56]. 

In view of their reduction potential, flavonoids have also been shown to interact with enzymes either unspecifically or specifically and modify their activity through reduction of metals in the active center. Of particular interest, because of their role in inflammatory conditions, is the reductive inactivation of lipoxygenases, cyclo-oxygenases, myeloperoxidase, and xanthine oxidase. In view of prooxidant activity of the enzymes, their inhibition by polyphenols may be regarded as an indirect antioxidation action. The list of enzymatic activities inhibited by flavonoids and other polyphenols also include phospholipase A2, protein kinases, metalloproteinases, drug metabolism enzymes, and telomerase, as reviewed elsewhere (Frade et al, 2005). 

Morel I, Lescoat G, Cillard P, CiUard J. Role of flavonoids and iron chelation in antioxidant action. Methods Enzymol 1994 234 437-443. 

Nagata H, Takekoshi S, Takagi T, Honma T, Watanabe K. Antioxidative action of flavonoids, quercetin and catechin, mediated by the activation of glutathione peroxidase. Tokai J Exp Clin Med 1999 24 1-11. 

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