To investigate the therapeutic effects and potential mechanisms of Mulianmei（Causonis japonica）on ulcerative colitis（UC）induced by dextran sulfate sodium（DSS）in mice.

C57BL/6J male mice were randomly divided into blank group, DSS group, DSS + Mulianmei（Causonis japonica）low-dose group（50 mg/kg）, DSS + Mulianmei（Causonis japonica）high-dose group（100 mg/kg）and DSS + sulfasalazine（SASP）group. Body weight and disease activity index（DAI）were recorded every day. The length of colon was measured. Hematoxylin-Eosin（H&E）staining was used to examine colon tissue structure. Enzyme-linked immunosorbent assay（ELISA）was employed to measure the levels of tumor necrosis factor-alpha（TNF-α）and interleukin -1beta（IL-1β）in colon tissues. The intestinal permeability of mice was detected by fluorescein isothiocyanate（FITC）. The autophagosomes in the colon tissues of the mice were detected by using transmission electron microscopy. The expression of microtubule-associated protein light chain 3（LC3）protein was detected by immunofluorescence staining. Western blot was used to detect the expressions of tight junction proteins and adenosine 5’-monophosphate-activated protein kinase（AMPK）/mammalian target of rapamycin（mTOR）signaling pathway related proteins in colon tissue of mice.

DSS group, DSS + Mulianmei（Causonis japonica）low-dose group（50 mg/kg）, DSS + Mulianmei（Causonis japonica）high-dose group（100 mg/kg）and DSS + sulfasalazine（SASP）group. Compared with those in the blank group, the body weight of mice in the DSS group was decreased（P < 0.01）, the DAI score was increased（P < 0.01）and the colon tissue showed severe pathological damage. The expression levels of tight junction proteins ZO-1（P < 0.05）and Occludin（P < 0.01）were reduced in the colon tissue and the expression levels of TNF-α and IL-1β in serum were significantly increased（P < 0.01）. The protein expression levels of LC3 and p-AMPK/AMPK were decreased（P < 0.01）and mTOR/mTOR protein was increased（P < 0.01）at the same time. Compared with those in the DSS group, the body weights of the mice in the DSS + Mulianmei（Causonis japonica）low-dose and high-dose groups were increased（P < 0.01）, the DAI scores were decreased（P < 0.01）, and the colon tissue damage was alleviated. The levels of TNF-α（P < 0.01）and IL-1β（P < 0.05）in serum were significantly decreased. The number of autolysosomes increased and the autophagosomes were clearly visible. The protein levels of LC3 and p-AMPK/AMPK were increased（P < 0.01）, and the expression of p-mTOR/mTOR was decreased（P < 0.01）. Compared with those in the DSS + Mulianmei（Causonis japonica）low-dose and high-dose groups, after the intervention of Mulianmei（Causonis japonica）and AMPK selective inhibitor, the colon of UC mice was shortened, the DAI score was increased, the protein levels of p-AMPK/AMPK were decreased（P < 0.01）, and the protein levels of p-mTOR/mTOR protein were increased（P < 0.01）.

Mulianmei（Causonis japonica）enhances autophagy by activating AMPK/mTOR signaling pathway to alleviate the symptoms of UC in mice.