The purpose of this study is to examine the toxic effects caused by xanthine oxidase/hypoxanthine(XO/HX) and the effects of herbal extracts such as JHYJ and GJHYJ on the treatment of the toxic effects. For this purpose, experiments with the cultured hippocampal cells from new born mice were done. The results of these experiments were as follows. 1. XO/HX, a oxygen radical-generating system, decreased the survival rates of the cultured cells on XTT assay and INT assay, the amount of DNA syntheses, and the amount of neurofilaments, and increased the lipid peroxidation. 2. JHYJ and GJHYJ have the efficacy of increasing the survival rates of the cultured cells. 3. JHYJ and GJHYJ have the efficacy of increasing the amount of neurofilaments and of decreasing the lipid peroxidation. 4. JHYJ and GJHYJ have the efficacy of increasing the amount of DNA syntheses. From the above results, it is suggested that Jihwangyeumja and Gamijihwangyeumja have marked efficacy as a treatment for the damages caused by the XO/HX-mediated oxidative stress. And Jihwangyeumja and Gamijihwangyeumja are thought to have certain pharmacological effects. Further dinical study of this pharmacological effects of Jihwangyeumja and Gamijihwangyeumja should be complemented.