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Effects of dietary antioxidants on human DNA ex vivo
Yim-Tong Szeto1, Iris F F Benzie
1Department of Nursing and Health Sciences, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, People's Republic of China.
Abstract:
The protective effect of fruits and vegetables against cancer is well established. It is believed that this effect is mediated by antioxidants and decreased oxidative damage to DNA. However, the identity of the antioxidant(s) responsible is not clear. Moreover, a potentially damaging pro-oxidant effect of some antioxidants has been reported. In this study the ex vivo effects of several dietary antioxidants, including quercetin, various catechins, ascorbic acid and alpha-tocopherol, were investigated, at concentrations up to 200 microM, using the single cell gel electrophoresis (comet) assay for DNA damage. Lymphocytes from three healthy subjects were pre-incubated with these antioxidants, and the comet assay was performed on treated, untreated, challenged and unchallenged cells in parallel, oxidant challenge being induced by 5 min exposure to hydrogen peroxide (final concentrations H2O2: 30, 45, or 60 microM). Results using this ex vivo cellular assay showed protection by some antioxidants (quercetin, caffeic acid), no effect by some (catechin, epicatechin, catechin gallate, epicatechin gallate) and an apparently damaging effect by others (epigallocatechin, epigallocatechin gallate). Damage may have been caused by production of H2O2 from these polyphenolics. Neither ascorbic acid nor alpha-tocopherol protected or damaged DNA. Further study of the role of quercetin and caffeic acid in DNA protection is needed.
Insights
Dietary antioxidants like quercetin show promise in protecting DNA from damage. However, some antioxidants may be harmful, necessitating further research into their precise roles in cancer prevention.
Area of Science:
- Nutritional Science
- Molecular Biology
- Toxicology
Background:
- Fruits and vegetables are known to protect against cancer, likely due to antioxidants reducing DNA damage.
- The specific antioxidants responsible and potential pro-oxidant effects remain unclear.
Purpose of the Study:
- To investigate the ex vivo effects of dietary antioxidants on DNA damage.
- To assess the protective or damaging potential of quercetin, catechins, ascorbic acid, and alpha-tocopherol.
Main Methods:
- Utilized the single cell gel electrophoresis (comet) assay on human lymphocytes.
- Cells were pre-incubated with antioxidants and exposed to hydrogen peroxide (H2O2) to induce oxidative stress.
Main Results:
- Quercetin and caffeic acid demonstrated protective effects against DNA damage.
- Epigallocatechin and epigallocatechin gallate showed a damaging effect, possibly via H2O2 production.
- Ascorbic acid and alpha-tocopherol had no significant effect on DNA integrity.
Conclusions:
- Certain dietary antioxidants, like quercetin, may offer DNA protection.
- The pro-oxidant potential of some polyphenolics warrants further investigation.
- More research is needed on quercetin and caffeic acid's role in DNA protection.