Objective:To observe therapeutic effect and mechanism of Dandelion extract in rat ulcerative colitis（UC） model.Method: Sixty rats were randomly divided into control group

model group

sulfasalazine group（SASP

400 mg·kg-1）

high-dose

medium-dose and low-dose group of Dandelion extract（50

100

150 mg·kg-1）.Trinitrobenzene sulphonic acid（TNBS

100 mg·kg-1） was instilled into the colon of rats to induce ulcerative colitis.These groups were given relevant drugs with 2 mL

once a day for 14 d.On the day 14

the rats were sacrificed to collect blood and colon specimens.The morphology and histological changes of mucous membrane were observed

ELISA was performed to detect the levels of interleukin-6（IL-6）

interleukin-10（IL-10） and tumor necrosis factor-α（TNF-α）

and streptavidin-perosidase（SP） was performed to detect expression of nuclear factor-κB（NF-κB） p65.Result: Compared with model group（7.89±0.31

12.17±1.56）

the Dandelion extract at high-dose

medium-dose and low-dose could reduce the morphologic score of mucous membrane significantly（5.11±0.43）

（6.11±0.31）

（7.01±0.38）

（P<0.05）

and histological changes was（8.11±1.23）

（9.37±1.12）

（10.12±1.32）respectively

（P<0.05）.The level of IL-6 and TNF-α was decreased（68.53±18.21）

（71.41±13.38）

（80.24±15.29）

（36.27±8.35）

（46.29±9.32）

（64.18±8.98） ng·L-1 compared with model group（89.91±19.13）

（71.27±8.81） ng·L-1（P<0.05

P<0.01）.Expression of NF-κB p65 was reduced from（0.411±0.086）% to（0.301±0.038）%

（0.351±0.053）%

（0.389±0.041）%（P<0.05

P<0.01）.But there was no obvious difference between Dandelion extract high-dose group and SASP group.Conclusion: These results indicated that Dandelion extract has effects on ulcerative colitis.