This study was performed to elucidate the possible antioxidative effects of several wild plant extracts. Wild plants were extracted with methanol or water using general method. In first experiments, antioxidative effects were measured by lipid peroxidation using rat brain homogenate. Coptis japonica extract showed the highest antioxidative activity among the 15 wild plant extracts. In second experiments, rats were fed on the semipurified diets with or without Coptis japonica extracts at the level of 0.5% for 4 weeks. MDA production of liver homogenate were significantly lower in the rats fed Coptis japonica extracts (P<0.05). Cytosolic catalase. GPX, and SOD activities were not changed, whereas the activities of GST and glutathione level were significantly higher in rats fed Coptis japonica extracts (P<0.05). These results suggest that Coptis japonica extract has an antioxidative effect through increasing GST activity and glutathione level and decreasing MDA production.