RADIOPROTECTIVE EFFECT OF ANTIOXIDATIVE FLAVONOIDS IN GAMMA-RAY IRRADIATED MICE

The anticlastogenic effect of 12 structurally different flavonoids was investigated in whole body gamma-ray irradiated mice. Each flavonoid was administered to ICR male mice by a single gastric intubation (5 mu mol/kg) 6 h before gamma-ray irradiation (1.5 Gy) and the frequency o f micronucleated reticulocytes (MNRETs) in peripheral blood was determ ined. In order to elucidate the mechanism of the anticlastogenic effec t of these flavonoids, their antioxidative activities were examined by the thiobarbituric acid method using methyl linoleate and Fenton's re agent (Fe2+/H2O2). Of the 12 flavonoids, luteolin had the most marked effect on reducing the frequencies of MNRETs and also inhibiting lipid peroxidation. However, quercetin tetramethylether, which has methoxy groups instead of hydroxyl groups at the 3,7,3',4'-positions, and phlo retin with an open C-ring showed the least anticlastogenic and antioxi dative activity. A good correlation (r = 0.717, P < 0.01) was observed between the anticlastogenic activity and the antioxidative activity o f the 12 flavonoids. These results suggest that the radioprotective ef fect of flavonoids in mice may be attributed to the hydroxyl radical s cavenging potency in a direct or an endogenous enzyme mediated manner.