The polyphenol derivative 5,2′‐dibromo‐2,4′,5′‐trihydroxydiphenylmethanone (LM49) synthesized by our group can effectively ameliorate unilateral ureteral obstruction‐ and folic acid‐induced renal fibrosis, which is connected to the suppression of high‐mobility group box 1 (HMGB1)‐induced inflammation and tubular epithelial cell necrosis. Here, HMGB1 is linked to Ureteral obstruction.