Objective: To study the active mechanism of Yiyi Fuzi Baijiang San in treating ulcerative colitis in antioxidant stress signal pathway. Method: Sixty male C57BL/6J mice were randomly divided into six groups

normal group

model group

Mesalazine group

and low

medium and high-dose Yiyi Fuzi Baijiang San groups. Except for the normal group

the other groups of mice were included in the acute ulcerative colitis model. At the 3rd day of modeling

low

medium and high-dose Yiyi Fuzi Baijiang San groups were given liquid Chinese medicine with doses of 5.24

10.48

20.96 g·kg-1. The Mesalazine drug group was treated with 0.82 g·kg-1 of mesalazine solution. Normal group and model group were intragastrically given the same volume of double distilled water. A course of treatment was 7 days. Weight changes

stool traits and fecal occult blood of the mice were observed

and the disease activity index (DAI) score curve was drawn for each group of mice. The mice were put to death on the 10th day of the experiment; colon tissues were taken for hematoxylin-eosin(HE) staining and HI scoring; the contents of total superoxide dismutase (T-SOD) and malondialdehyde (MDA) in intestinal tissues were measured; and the expression of Nrf2 and hemeoxygenase (HO)-1 protein in colon tissues were detected by immunohistochemical method. The changes in Nrf2 mRNA expression in tissues were detected by RT-PCR. Result: Compared with the model group

the DAI score of the drug-treated mice decreased significantly (P<0.05)

the histological structure of the intestinal mucosa was survived

and the HI score decreased significantly (P<0.05). The content of T-SOD in the model group was significantly lower (P<0.05)

and significantly higher in the drug groups (P<0.05); the content of MDA in the model group was significantly higher (P<0.05) and decreased in the drug group (P<0.05). Immunohistochemistry showed that the expression of Nrf2 was significantly increased in the drug-treated groups compared with the model group (P<0.05). Compared with the model group

the expression of HO-1 in the low-dose group was not significantly different. High-dose group was significantly higher (P<0.05). RT-PCR detection of Nrf2 mRNA expression found that compared with the model group

high-dose group showed a high expression (P<0.05). Conclusion: Yiyi Fuzi Baijiang San can up-regulate the expression of Nrf2.Its downstream antioxidant protein HO-1 can increase the Nrf2 mRNA expression and have a therapeutic effect on ulcerative colitis.