Abstract: AIM: To evaluate the antitumor effects and its possible mechanisms of total flavonoids of Eucommia ulmoides on tumor-bearing mice. METHODS: H₂₂ tumor-bearing mice were used as tumor model.Different doses of total flavonoids of Eucommia ulmoides were ig administered to the tumor-bearing mice once a day for continuous 12 d.Tumor growth was measured and tumor growth inhibition rate (IR) was calculated. Serum SOD and MDA concentrations were detected. The growth and pathomorphologic changes of tumor cell were observed through pathological sections. The protein expression level of Bcl-2 and Bax were detected by immunohistochemistry. RESULTS: Total flavonoids of Eucommia ulmoides inhibited the hepatocarcinoma H₂₂ transplantation tumor.Compared with the control group,the tumor formation was significantly retarded and tumor growth was inhibited in total flavonoids of Eucommia ulmoides treated groups.The inhibitory rates were 35.90%, 44.70% and 47.60% in three groups treated with low, middle, and high dosages of total flavonoids of Eucommia ulmoides, respectively. Compared with the control group,the levels of SOD were increased in total flavonoids of Eucommia ulmoides treated groups in a does-dependent manner(P<0.05). Pathology revealed that necrotic area of total flavonoids of Eucommia ulmoides treated groups and cyclophosphamide group was larger than the control group. Immunohistochemistry showed that the expression of Bax protein was increased and the expression of Bcl-2 protein was reduced in xenograft tumor tissues after total flavonoids of Eucommia ulmoides treatment. CONCLUSION: Total flavonoids of Eucommia ulmoides has significant inhibition on tumor growth in vivo, which is probably related to scanvenging oxygen free radicals and the down-regulation of Bcl-2 expression and up-regulation of Bax expression.

Key words: total flavonoids of Eucommia ulmoides, tumor, mouse, SOD, MDA, pathological section, immunohistochemistry