Quercetin antioxidant

Shutenko Z, Henry Y, Pinard E, Seylaz J, Potier P, Berthet F. 1999. Influence of the antioxidant quercetin in vivo on the level of nitric oxide determined by electron paramagnetic resonance in rat brain during global ischemia and reperfusion. Biochem Pharmacol 57 199-208. 

Suzuki Y, Ishihara M, Segami T, Ito M. Anti-mcer effects of antioxidants, quercetin, alpha-tocopherol, nifedipme and tetracycline in rats. Jpn J Pharmacol 1998 78(4) 435 1. 

Evaluation of olive- and grape-based natural extracts as potential preservatives for food was carried out by Serra et al. (2008). The antimicrobial activities of two waste-derived extracts, from olive oil and wine production, both rich in polyphenols, and three standard well recognized antioxidants (quercetin, hydroxytyrosol, and oleuropein) were investigated against five microbial species (Escherichia coli, Salmonella poona, Bacillus... 

Alkoxyl radicals react with a variety of antioxidants and biological compounds, such as f-butoxyl radical reaction with a range of fatty acids, generating t-butanol and a fatty acid radical via hydrogen abstraction [135]. Introducing unsaturated bonds into the fatty acids was seen to increase the abstraction rate constant. These radicals have also been seen to react with the antioxidants quercetin, crocin and crocetin, ascorbate and Trolox, as well as with the DNA bases, thymidine and adenosine [ 131 ]. In the case of quercetin its phenoxyl radical was observed, and this would be expected to occur for Trolox as weU, though the authors used competition kinetics to monitor this reaction rather than direct monitoring of the product. 

HoUman PCH, vandeiGaag M, Mengelers MJB, van Trijp JMP, deVries JH, Katan MB. Absorption and disposition kinetics of the dietary antioxidant quercetin in man. Free Radic Biol Med 1996 21 703-707. 

HoUman PCH, van Trijp JMP, Buysman MNCP, Gaag MS, Menglers MJB, deVries JHM, Katan MB. Relative hioavailablity of the antioxidant quercetin from various foods in man. FEBS Lett 1997 418 152-156. 

Fig. 16.4 Interaction between quercetin (Quer) and iron and the balance between pro-oxidative and antioxidative effects. Quercetin may reduce Fe(H20) to yield Fe(H20) active in the Fenton region forming hydroxyl radicals ( OFI) or alkoxyl radicals ( OR), in effect being pro-oxidative. In contrast, quercetin may form a complex with iron(II), inactive in reducing FI2O2 to OFI, but rather oxidised in the quercetin ligand, in effect being antioxidative. Quer (-H) is the phenoxyl radical.

For aqueous solutions, ascorbate can be included in the hierarchy, while a-tocopherol has to be replaced by its water-soluble analogue trolox, which is often assumed to have the same standard reduction potential. The ordering of the antioxidants based on the two different determinations of E in water is rather similar, and it should be noted that ascorbate is the antioxidant which will regenerate the other antioxidants, with the ascorbate itself ending up being oxidised. In contrast to what was observed for DMF, the ordering in water predicts that quercetin could regenerate a-tocopherol from its oxidised form. 

In the water-like solvent tert-butyl alcohol, a-tocopherol was found to prevent lipid oxidation, showing a distinct lag-phase for oxygen consumption. This was in contrast to quercetin or epicatechin, which were only weak retarders of lipid oxidation without any clear antioxidative effect. Quercetin or epicatechin, when combined with a-tocopherol, increased the lag-phase for oxygen consumption as seen for a-tocopherol alone. The stoichiometric factor for a-tocopherol, a-TOH, as chain-breaking antioxidant has the value n = 2 according to the well-established mechanism ... 

Flavonoids are chain-breaking antioxidants in lipid-like solvents like chlorobenzene, although the k(inh) is smaller than for a-tocopherol and the lag-phase accordingly less evident. For peroxidating lipids in chlorobenzene the clear lag-phase for a-tocopherol became longer when quercetin or catechin were present. The effect appears to be additive and a regeneration of a-tocopherol by quercetin or catechin in this lipid-like solvent should rather be termed a co-antioxidative effect (Pedrielli and Skibsted, 2002). 

PEDRiELLi p and SKIBSTED L H (2002) Antioxidant syneigy and regeneration effect of quercetin, (-)epicatechin, and (+)-catechin on a-tocopherol in homogeneous solutions of peroxidating methyl linoleate, JAgric Food Chem, 50, 7138-44. 

PEDRIELLI p, PEDULLi G F and SKIBSTED L H (2001a) Antioxidant mechanism of flavonoids. Solvent effect on rate constant for chain-braining reaction of quercetin and epicatechin in autoxidation of methyl linoleate, JAgric Food Chem, 49, 3034-40. 

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. 

Morel, I., Lescoat, G., Cogrel, P., Sergent, O., Pasdeloup, N., Brissot, P., Cillard, P. and Cillard, J. (1993). Antioxidant and iron chelating activities of the flavonoids catechin, quercetin and diosmetin on iron-loaded rat hepatocyte cultures. Biochem. Pharmacol. 45, 13-19. 

Quercetin is a naturally occurring flavonoid with both antioxidant and prooxidant activities (Scheme 10.12).90 It has been demonstrated in a variety of bacterial and mammalian mutagenicity experiments that quercetin has mutagenic properties that could be related to quinoid formation.91,92 Quercetin is initially oxidized to an o-quinone, which rapidly isomerizes to di-QMs that could also be called extended... 

An extract from Lactuca indica showed significant free radical scavenging activity, and protected phixl74 supercoiled DNA against strand cleavage and reduced oxidative stress in human promyelocytic leukemia HL-60 cells. On account of protocatechulic acid, methyl p-hydroxybenzoate, caffeic acid, 3,5-dicaffeoylquinic acid, luteolin 7-O-fT glucopyranoside, and quercetin 3-0-(3-g 1 ucopyranoside are the major antioxidative constituents (111). 

Hollman PC, van Trijp JM, Mengelers MJ, de Vries JH and Katan M B. 1997. Bioavailability of the dietary antioxidant flavonol quercetin in man. Cancer Lett 114(1—2) 139—140. 

Boots AW, Haenen GRMM and Bast A. 2008. Health effects of quercetin From antioxidant to nutraceutical. 

People in France eat a lot of fatty foods but suffer less from fatal heart strokes than people in the northern regions of Europe or in North America, where wine is not consumed on a regular basis ( French paradox ). There is an increased favorable effect from red wine. The unique cardioprotective properties of red wine are due to the action of flavonoids, which are minimal in white wine. The best-researched flavonoids are resveratrol and quercetin, which confer antioxidant properties more potent than a-tocopherol. 

It must be noted that the inhibitory effects of flavonoids and other antioxidants in nonhomogenous biological systems can depend not only on their reactivities in reactions with free radicals (the chain-breaking activities) but also on the interaction with biomembranes. Thus, Saija et al. [137] compared the antioxidant effects and the interaction with biomembranes of four flavonoids quercetin, hesperetin, naringen, and rutin in iron-induced... 

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