Effects of blueberry extracts on DNA damage levels and phase II enzyme activities in rats.

Abstract

Blueberry extracts been shown to reduce oxidative stress and increase phase II enzyme activities in vitro. We examined these effects in vivo. Male Sprague-Dawley rats (n=8 per group) were fed AIN-93 or modified AIN-93 diets for 3 weeks. Modified diets were 10% freeze dried blueberries substituted for sucrose (BLU), blueberry polyphenol extract and sugars to match the 10% blueberry diet (POLY), sugars equivalent to the 10% blueberry diet, 1% blueberry flavonoids (1% FL) and 0.2% blueberry flavonoids. The polyphenol extract was obtained using a 40:40:20:0.1 (v:v:v:v) ratio of acetone/methanol/water/formic acid solution. By further purifying the polyphenol extract with an Oasis HLB cartridge then eluting with acidified methanol, total flavonoids were obtained. Liver and colon mucosa glutathione-S-transferase (GST) and quinone reductase (QR) and liver UDP-glucuronosyltransferase (UGT) activities were measured as were urinary F2-isoprostanes and liver and lymphocyte DNA damage. GST, QR and UGT activities were not significantly increased at p<0.05 by blueberries or blueberry fractions, but some slight increases in activity were seen. For example, compared to controls, the BLU, POLY, and 1% FL groups had 28%, 27% and 24% higher GST activity in liver tissue. DNA damage assessed with the Comet assay was lowest for both liver and colon mucosa in the 1%FL group, but results were not significant. This study shows that in vivo results do not always agree with in vitro findings and that extremely high doses may be required to elicit significant effects. Support: GA FOODPAC, GA Ag Exp Sta., GA Blueberry Growers Assoc.