Effects of quercetin and quercetin-3-O-glycosides on oxidative damage in rat C6 glioma cells

doi:10.1016/S1382-6689(02)00129-1

Environmental Toxicology and Pharmacology

Volume 13, Issue 1, January 2003, Pages 47-53

https://doi.org/10.1016/S1382-6689(02)00129-1 Get rights and content

Abstract

Flavonoids are reported to be powerful antioxidants in cell free systems. They naturally occur as glycosides rather than as aglycon. In this study the ability of the flavonoid quercetin and its glycosides, quercetin-3-O-rutinoside (rutin), quercetin-3-O-glucoside and quercetin-3-O-(6″-O-acetyl)-glucoside, to protect in vitro rat C6 glioma cells from oxidative damage induced by cumene hydroperoxide was investigated. Cumene hydroperoxide induced cell death and lipid peroxidation. The cytotoxicity of cumene hydroperoxide could be prevented by the radical scavenger dimethyl thiourea and the ferric iron chelator deferoxamine, indicating that its cytotoxic activity is related to the generation of reactive oxygen radicals in the ferrous iron dependent Fenton reaction. Quercetin, in a concentration range of 10–100 μM, but neither rutin nor the other two glycosides, were able to protect C6 cells from cytotoxicity and lipid peroxidation. Furthermore, cytoprotective concentrations of quercetin proved to be cytotoxic itself. These results call in question potential beneficial effects of dietary intake or therapeutic use of naturally occurring flavonoids.

Introduction

Flavonoids are polyphenolic components of higher plants known to be excellent antioxidants in vitro. Dietary flavonoids have been shown to prevent lipid peroxidation, to scavenge reactive oxygen species, to chelate iron ions, essential for the generation of hydroxyl radicals, and to inhibit NADPH-dependent oxidases and consequently superoxide anion production (Catapano, 1997, Rice-Evans et al., 1997, Robak and Gryglewski, 1996). Evidence for the potential role of oxidative stress in various diseases and pathophysiological processes suggests that the dietary intake and the therapeutic use of flavonoids may have positive health effects (Halliwell, 1996, Hollman and Katan, 1999, Ignatowicz and Rybczyńska, 1994).

Flavonoids usually occur as glycosides. Numerous studies have been published on the antioxidative activities of flavonoid aglycons in cell free systems and some (e.g. Afanas'ev et al., 1989, Rice-Evans et al., 1996, Zielinska et al., 2001) also included flavonoid glycosides. Investigations about the efficacy of flavonoids to protect mammalian cells from reactive oxygen induced damage, however, are scarce. Thus, the goal of the present study was to investigate the ability of the flavonoids quercetin, quercetin-3-O-rutinoside (rutin), quercetin-3-O-glucoside and quercetin-3-O-(6″-O-acetyl)-glucoside (Fig. 1) to protect in vitro rat C6 glioma cells from oxidative damage induced by cumene hydroperoxide. Quercetin (3,3′,4′,5,7-pentahydroxyflavone) and rutin belong to the most prominent flavonoids in the human diet. Quercetin-3-O-acetylglucoside and quercetin-3-O-glucoside were isolated from the flowers of the Canadian goldenrod (Solidago canadensis) and the garden tulip (Tulipa gesneriana), respectively (Budzianowski et al., 1990, Budzianowski, 1991).

Section snippets

Chemicals

Fig. 1 shows the chemical structure of the flavonoids examined. Quercetin-3-O-(6″-O-acetyl)-glucoside was isolated and identified from goldenrod flowers, S. canadensis var. scabra (Asteraceae) (Budzianowski et al., 1990). Quercetin-3-O-glucoside was isolated and identified from T. gesneriana flowers (Budzianowski, 1991). These compounds were of high purity as judged by their ¹H and ¹³C NMR spectra, which showed no signals of impurities. Quercetin dihydrate, rutin and deferoxamine mesylate were

Cytotoxicity of cumene hydroperoxide

Cumene hydroperoxide promoted loss of growth arrested cells in a time dependent manner. Fig. 2 shows that the cells had to be exposed for at least 4 h to induce the concentration dependent maximum cytotoxic effect. Therefore, C6 cells were treated with cumene hydroperoxide for 24 h to ensure maximum cytotoxic efficiency. A 24 h exposure to cumene hydroperoxide induced cell death with an EC₅₀-value of 44±9.5 μM (mean±S.E., n=8).

The cytotoxic action of cumene hydroperoxide could be inhibited by

Discussion

Cumene hydroperoxide can participate in the iron dependent Fenton reaction to generate potent oxidising radicals (Starke and Farber, 1985). Due to its lipophilicity, the action of cumene hydroperoxide is supposed to be largely restricted to the cell membrane (Vroegop et al., 1995). In the present study cumene hydroperoxide has been shown to induce lipid peroxidation and cytotoxicity in C6 cells. Cytotoxicity could be prevented by the ferric iron chelator deferoxamine and the radical scavenger

Acknowledgements

This work was supported by a study visit grant to M. Zielińska from the Deutscher Akademischer Austauschdienst (DAAD).

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Effects of quercetin and quercetin-3-O-glycosides on oxidative damage in rat C6 glioma cells

Abstract

Introduction

Section snippets

Chemicals

Cytotoxicity of cumene hydroperoxide

Discussion

Acknowledgements

Biochem. Pharmacol.

Toxicol. Lett.

Food Chem. Toxicol.

Phytochemistry

Methods Enzymol.

FEBS Lett.

FEBS Lett.

Blood

Food Chem. Toxicol.

J. Biol. Chem.

Free Radic. Biol. Med.

Trends Plant Sci.

Free Radic. Biol. Med.

Free Radic. Biol. Med.