Abstract: Objective To explore effects of Dihydromyricetin (DHM) on experimental colitis and regulatory B cells(Breg) of mice. Methods The mice were randomly divided into control group, DSS group, DSS⁺DHM group and DSS⁺ mesalazine group (4% DSS for 7 days). After 7 days, the mice were respectively gavaged with water (0.2 mL/d),DHM (40 mg/kg·d) and mesalazine (520 mg/kg·d) for 7 consecutive days and the disease activity index (DAI) was continuously recorded. The animals were sacrificed on the 14th day and the colon length was measured. The colon tissue sections were microscopied with HE staining. CD19⁺B lymphocytes and Breg(CD19⁺CD5⁺CD1d⁺) were determined by flow cytometry in splenic single cell suspension; real-time fluorescent quantitative PCR (RT-qPCR) was used to detect the relative mRNA level of IL-10,TGF-β,IL-6 and IFN-γin spleen cells. The effect of DHM on the proliferation of spleen cells was measured by CCK8. DHM (40 μmol/L) was selected to act on the spleen cell suspension for 24 h. flow cytometry was used to detect the ratio of Breg (CD19⁺CD5⁺CD1d⁺). Results Compared with the normal group, DAI and pathological score of DSS group were significantly higher, and the colon length was significantly decreased(P＜0.05); The proportion of CD19⁺ B cells vs. Breg (CD19⁺CD5⁺CD1d⁺) was significantly decreased, the inflammatory factors were significantly increased, and the anti-inflammatory factors were obviously decreased (P＜0.05). Compared with DSS group, DSS⁺DHM group and DSS⁺Mesalazine group significantly reversed the situation (P＜0.05); It was fond in vitro experiment that DHM significantly promoted the proliferation of spleen cells and Breg (P＜0.05). Conclusions DDHM has obvious therapeutic effect in experimental colitis mice, which may be related to the promotion of Breg proliferation and of secretion of anti-inflammatory factors IL-10 and TGF-β.

Key words: dihydromyricetin(DHM), regulatory B cell(Breg), experimental colitis, cytokine