Related Experiment Videos
Dietary antioxidants fail in protection against oxidative genetic damage in in vitro evaluation
M Sun1, H Sakakibara, H Ashida
1Department of Life Science, Graduate School of Science and Technology, Kobe University, Japan.
Abstract:
Carcinogenesis is believed to be induced through the oxidative damage of DNA, and antioxidants are expected to suppress it. So, the polyphenolic antioxidants in daily foods were investigated to see whether they protect against genetic damage by active oxygen. In the evaluation, we used a bioassay and a chemical determination, a Salmonella mutagenicity test for mutation by a N-hydroxyl radical from one of the dietary carcinogens 3-amino-1-methyl-5H-pyrido[4,3-b]indole and the formation of 8-hydroxyl (8-OHdG) from 2'-deoxyguanosine (2'-dG) in a Fenton OH-radical generating system. Thirty-one antioxidants including flavonoids were compared in terms of radical-trapping activity with bacterial DNA and 2'-dG. Antioxidants inhibited the mutation but the IC50 values were in the mM order. Against 8-OHdG formation, only alpha-tocopherol had a suppressive effect with an IC50 of 1.5 microM. Thus, except alpha-tocopherol, the dietary antioxidants did not scavenge the biological radicals faster than bacterial DNA and intact 2'-dG, indicating that they failed to prevent oxidative gene damage and probably carcinogenesis.
Insights
Dietary antioxidants, like flavonoids, were tested for their ability to prevent DNA damage from active oxygen species. Most failed to protect against genetic damage, suggesting they may not prevent cancer initiation.
Area of Science:
- Biochemistry
- Molecular Biology
- Nutritional Science
Background:
- Carcinogenesis is linked to oxidative DNA damage.
- Antioxidants are hypothesized to suppress cancer by preventing this damage.
- Polyphenolic antioxidants from food are common dietary components.
Purpose of the Study:
- To investigate if dietary polyphenolic antioxidants protect against oxidative DNA damage.
- To evaluate the radical-trapping activity of 31 antioxidants, including flavonoids.
- To assess the efficacy of these antioxidants in preventing mutations and 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation.
Main Methods:
- Utilized a Salmonella mutagenicity test to assess DNA mutation induction by N-hydroxyl radicals.
- Employed a Fenton OH-radical generating system to study 8-OHdG formation from 2'-deoxyguanosine (2'-dG).
- Compared the radical-scavenging activity of 31 antioxidants against bacterial DNA and 2'-dG.
Main Results:
- Antioxidants showed inhibitory effects on mutation with IC50 values in the millimolar (mM) range.
- Only alpha-tocopherol significantly suppressed 8-OHdG formation, with an IC50 of 1.5 micromolar (µM).
- Most dietary antioxidants did not scavenge biological radicals faster than DNA and 2'-dG.
Conclusions:
- Dietary antioxidants, excluding alpha-tocopherol, were ineffective at preventing oxidative gene damage.
- The tested antioxidants failed to scavenge radicals efficiently enough to protect DNA.
- These findings suggest that common dietary antioxidants may not prevent carcinogenesis initiated by oxidative stress.