Flavonoids inhibit the genotoxicity of hydrogen peroxide (H2O2) and of the food mutagen 2-amino-3-methylimadazo[4,5-f]-quinoline (IQ) in lymphocytes from patients with inflammatory bowel disease (IBD)

Inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC) is a chronic inflammatory gastrointestinal autoimmune condition with an inappropriate immune response. We investigated DNA damage induced in vitro in lymphocytes from IBD patients caused by oxidative stress through H2O2 and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and whether the plant flavonoids, quercetin and epicatechin, found in fruits, tea and soybeans could effectively reduce such stress. Lymphocytes from IBD patients and healthy volunteers were treated with 50 mu g/ml H2O2 or IQ in the presence of quercetin (0-250 mu g/ml) or epicatechin (0-100 mu g/ml). Flavonoid supplementation (250 mu M quercetin or 100 mu M epicatechin) caused an overall significant decrease of induced DNA damage resulting in a 48.6% (P < 0.001) reduction of H2O2-induced and a 43% (P < 0.001) reduction of IQ-induced DNA damage within the patient groups; for the control groups, reductions in DNA damage were 35.2 and 57.1%, respectively (both, P < 0.001). There was less induced DNA damage within lymphocytes from UC patients compared to CD patients for both series of experiments (H2O2 and quercetin, IQ and epicatechin). In conclusion, flavonoids dramatically reduced oxidative stress in vitro in lymphocytes from IBD patients and healthy individuals. Thus, flavonoids could be very effective in the treatment of oxidative stress and encouraged in the diet of IBD patients.