Comparison of the Ability of Myricetin and Quercetin to Modulate the Oxidative DNA Damage Induced by Heterocyclic Amines

Ana Isabel Haza,Angel Lui Coto,Paloma Morales

doi:10.4236/fns.2011.24051

Abstract

The aim of the present study was to compare the ability of the myricetin and quercetin to modulate the oxidative DNA damage induced by 2-amino-3, 8- dimethylimidazo [4,5-f] quinoxaline (8-MeIQx), 2-amino- 3, 4, 8- trimethylimidazo [4, 5-f]-quinoxaline (4,8-diMeIQx) and 2-amino-1-methyl-6-phenyl-imidazo [4,5-b] pyridine (PhIP), in human hepatoma cells. DNA damage (strand breaks and oxidized purines/pyrimidines) was evaluated by the alkaline single-cell gel electrophoresis or comet assay. None of the myricetin and quercetin concentrations tested protected against 8-MeIQx, 4, 8-diMeIQx and PhIP-induced DNA strand breaks. The oxidized pyrimidines induced by 4, 8-diMeIQx and PhIP were reduced by myricetin but not by quercetin. Quercetin reduced the oxidized purines induced by 8-MeIQx and PhIP, while myricetin also reduced the induced by 4, 8-diMeIQx. One feasible mechanism by which myricetin and quercetin exert their protective effect towards HCAs-induced oxidative DNA could be related in part to the reduction of human CYP1A1. Another mechanism claimed to be responsible for the protective effect of myricetin and quercetin is the induction of phase II metabolizing enzymes such as UDP-glucuronyltrasferase (UGT). The ethoxyresorufin O-deethylation (CYP1A1) activity was moderately inhibited by myricetin, while little effect was observed by quercetin. On the contrary, quercetin showed the greatest increase on UDP-glucuronyltransferase activity. However, these are not the only mechanisms by which myricetin and quercetin exert their protective effect, other mechanisms such as stimulation of the repair of carcinogen-induced DNA damage and or the free radical scavenging efficiency have been also implicated. In conclusion, our results clearly indicate that myricetin was more efficient than quercetin to prevent DNA damage (oxidized purines and pyrimidines) induced by the three HCAs evaluated. This protective effect depends on the chemical structure of flavonoid and the mutagen studied.

Highlights

Strong and consistent epidemiologic evidence suggests a diet that includes regular consumption of fruits and vegetables, significantly reduces the risk of many cancers [1]
Results indicated that none of the myricetin (0.1 - 5 M) and quercetin (0.1 - 5 M) concentrations tested in presence or absence of formamidopyrimidine DNA glycosylase (Fpg) or Endo III, caused DNA damage per se
The aim of the present study was to compare the ability of the myricetin and quercetin to modulate the oxidative DNA damage induced by heterocyclic amines (HCAs) in human hepatoma cells using the single-cell gel electrophoresis (SCGE) assay

Summary

Introduction

Strong and consistent epidemiologic evidence suggests a diet that includes regular consumption of fruits and vegetables, significantly reduces the risk of many cancers [1]. Flavonoids are polyphenolic compounds, ubiquitous in plants, and found in significant quantities in vegetables, fruits, seeds, nuts and beverages such as tea and wine. Myricetin occurs in many plant-derived foodstuffs, notably tea, grapes and cranberries, while quercetin is found mainly in onions, apples and tea [2]. These flavonoids constitute an important group of phytochemicals that gained increased research attention since it was found that they could exert anticarcinogenic, antimutagenic, antiinflammatory, and antiviral actions [3]. Flavonoids are widely recognized as naturally occurring antioxidants, and they are suggested to act as chemopreventive compounds against tumors and cancer [5,6]

Objectives

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Results

Conclusion