Catalpol (CAT) mitigated triptolide (TP) induced liver injury in mice by modulating oxidative stress and lipid peroxidation. Mice were randomly divided into the following 5 groups (six mice per group): Vehicle control (Ctrl), TP 0.6 mg/kg (TP), TP 0.6 mg/kg + CAT 1.5 mg/kg (TP + CAT1.5), TP 0.6 mg/kg + CAT 3.0 mg/kg (TP + CAT3) and TP 0.6 mg/kg + CAT 4.5 mg/kg (TP + CAT4.5). (A) Body weight. (B) Liver index. (C) Serum ALT levels. (D) Serum AST levels. (E) Microphotograph of H&E-stained sections of liver tissues (Scale bars, 100/50 μm). (F) Serum LDH levels. (G) MDA content. (H) Representative DHE fluorescence staining of liver sections for ROS production. Scale bar, 31.7 μm. (I) Immunofluorescence staining of liver sections using antibody against 4-HNE. Scale bar, 31.7 μm. (J) Quantification of DHE and 4-HNE fluorescence image. (K) The relative concentrations of GSH, GSSG and GSH/GSSG ratio measured in liver tissues. Data are expressed as mean ± SD (n = 6); #P < 0.05 versus Ctrl, *P < 0.05 versus TP.