Mutation Research/Genetic Toxicology and Environmental Mutagenesis
Quercetin and myricetin protect against hydrogen peroxide-induced DNA damage (strand breaks and oxidised pyrimidines) in human lymphocytes
Introduction
Reactive oxygen species, from both endogenous and exogenous sources, may be involved in the aetiology of diverse human diseases, such as coronary heart disease, stroke, rheumatoid arthritis and cancer 1, 2. Diets rich in fruit and vegetables are associated with a reduced risk for these pathologies 3, 4, 5and protection has been attributed to antioxidant vitamins such as vitamin C, vitamin E and β-carotene 6, 7, 8, 9.
However, other dietary components may be important protective agents. Flavonoids are polyphenolic compounds, ubiquitous in plants, and found in significant quantities in vegetables, fruits, seeds, nuts and beverages such as tea and wine. Quercetin is the major flavonoid found in the average Western diet (16 mg/day). It is found mainly in onions, apples and tea [10]. Myricetin occurs in many plant-derived foodstuffs, notably tea, grapes and cranberries 10, 11. Silymarin, isolated from the milk thistle, Silybum marianum, is a hepatoprotective agent, used principally in the treatment of alcohol-induced liver toxicity [12]. The dietary intake for flavonoids in humans has been estimated to lie between 16 and 1000 mg/day 13, 14, but little is known of their absorption, distribution and metabolism.
Flavonoids have a number of biological effects in vivo and in vitro. They are anti-inflammatory, antiviral and antiallergic agents and can modulate a wide range of mammalian enzyme activities, such as cytochrome P450, epoxide hydrase, glutathione transferase, DNA and RNA polymerases and topoisomerase 15, 16. They are best known, however, for their antioxidant properties, and can act in vitro as reducing agents, hydrogen donors, free radical quenchers and metal ion chelators (17, 18, 19, 20). While this may account for the antimutagenic activities of flavonoids in experimental systems, relatively little is known about the potential cytoprotection afforded by these dietary components in humans.
This study compares the ability of the flavonoids, quercetin, myricetin and silymarin to modulate the DNA damage induced in human lymphocytes by oxygen free radicals.
Section snippets
Materials
α-Tocopherol, β-carotene, l-glutamine, histopaque 1077, myricetin, penicillin G, pyruvic acid, quercetin and streptomycin sulphate were from Sigma (Poole, UK). Silymarin was obtained from Aldrich Chemical Co. (Dorset, UK). Dutch modified RPMI 1640 medium containing 20 mM HEPES buffer was from ICN Flow (Irvine, UK). Fetal calf serum (FCS; batch 150) was obtained from Globepharm Ltd. (Surrey, UK). Nunc sterile tissue culture plastics were supplied by Gibco Life Technologies Inc. (Paisley, UK).
Results
The genotoxic effects of hydrogen peroxide and the protective ability of quercetin, myricetin and silymarin were assessed in normal human lymphocytes using the comet assay. The concentrations of flavonoids used were non-toxic [29]and DMSO, the vehicle used throughout, had no effect on either DNA strand breakage or base damage (data not shown). Neither hydrogen peroxide (200 μM) nor quercetin (50 μM), incubated either singly or in combination, affected human lymphocyte viability or cell number (
Discussion
Epidemiological studies suggest that dietary flavonoids protect against coronary heart disease and stroke 5, 34. The beneficial effects of flavonoids have been attributed to their antioxidant properties, including their ability to inhibit xanthine oxidase activity, to scavenge superoxide anions and hydroxyl radicals, and to inhibit lipid peroxidation in a variety of experimental systems 17, 20, 35, 36. Free radical scavenging efficiency is associated with the presence and number of hydroxy
Acknowledgements
The authors are grateful to Professor Ian Bremner for critically reviewing the manuscript.This work was funded by the Scottish Office Agriculture Environment and Fisheries Department and the Ministry of Agriculture Fisheries and Food.
References (55)
A review of epidemiological evidence that carotenoids reduce the risk of cancer
J. Nutr.
(1989)- et al.
Antioxidant micronutrients in cancer prevention
Hematol./Oncol. Clin. North Am.
(1991) - et al.
Vitamin E and cancer prevention
Am. J. Clin. Nutr.
(1991) - et al.
Randomised controlled trial of silymarin treatment in patients with cirrhosis of the liver
J. Hepatol.
(1989) - et al.
Chelating and free radical scavenging mechanisms of inhibitory action of rutin and quercetin in lipid peroxidation
Biochem. Pharmacol.
(1989) - et al.
Antioxidant and iron-chelating activities of the flavonoids catechin, quercetin and diosmetin on iron-loaded rat hepatocyte cultures
Biochem. Pharmacol.
(1993) - et al.
Structure–antioxidant activity relationships of flavonoids and phenolic acids
Free Radic. Biol. Med.
(1996) - et al.
Antioxidant properties of hydroxy-flavones
Free Radic. Biol. Med.
(1996) - et al.
The influence of cell growth, detoxifying enzymes and DNA repair on hydrogen peroxide-mediated DNA damage (measured using the comet assay) in human cells
Free Radic. Biol. Med.
(1997) - et al.
Glutathione reductase
Methods Enzymol.
(1985)
A microgel electrophoresis technique for the direct quantitation of DNA damage and repair in individual fibroblasts cultured on microscope slides
Mutation Res.
The kinetics of repair of oxidative DNA damage (strand breaks and oxidised pyrimidines) in human cells
Mutation Res.
Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study
Lancet
Protection of plasmid pBR322 DNA by flavonoids against single-strand breaks induced by singlet molecular oxygen
J. Photochem. Photobiol.
Genotoxicity of active oxygen species in mammalian cells
Mutation Res.
DNA damage by oxygen-derived species: its mechanisms and measurement in mammalian systems
FEBS Lett.
Inhibition of cytochrome P450 activity in rat liver microsomes by the naturally occurring flavonoid, quercetin
Arch. Biochem. Biophys.
Protection effect of flavonoids on drug-induced hepatotoxicity in vitro
Toxicology
Mechanism for the protective effects of silymarin against carbon tetrachloride-induced lipid peroxidation and hepatotoxicity in mice: evidence that silymarin acts both as an inhibitor of metabolic activation and as a chain-breaking antioxidant
Biochem. Pharmacol.
The effect of silymarin on plasma levels of malondialdehyde in patients receiving long-term treatment with psychotropic drugs
Curr. Ther. Res.
The protective role of polyphenols in cytotoxicity of hydrogen peroxide
Mutation Res.
Protective effect of epicatechin, epicatechin gallate, and quercetin on lipid peroxidation in phospholipid bilayers
Arch. Biochem. Biophys.
Oxygen radicals and human disease
Ann. Intern. Med.
Free radicals, antioxidants and human disease; where are we now?
J. Lab. Clin. Med.
Vegetables, fruit, and cancer
Cancer Causes Control
Vegetable and fruit consumption and cancer risk
Int. J. Cancer
Dietary flavonoids, antioxidant vitamins, and incidence of stroke
Arch. Intern. Med.
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