The aim of this study was to investigate the effects of tetrahydroberberine (THB) and tetrahydropalmatine (THP) on the expression of mouse liver cytochrome P450s, and evaluate their liver toxicity in mice. Real-time polymerase chain reaction (PCR) and western blot analyses were used to analyze the expression of major P450 isoforms. Liver toxicity was evaluated by measuring serum biochemical parameters and performing histopathological analysis. The real-time PCR results showed that THB induced Cyp1a2 (1.66 +/- 0.34 fold, P < 0.05), Cyp3a11 (1.57 +/- 0.24 fold, P < 0.05), and Cyp2e1 (1.75 +/- 0.97 fold, P < 0.05) mRNA expression, while THP inhibited Cyp1a2 (0.66 +/- 0.12 fold, P < 0.05) mRNA expression. The western blot results confirmed that the expression of CYP1A2, CYP3A, and CYP2E1 proteins in the mouse liver was induced by THB, whereas that of CYP1A2 was inhibited by THP. Toxicological studies showed that THB (40 mg/kg, oral gavage) increased mouse serum aspartate transaminase and total bilirubin, and liver malondialdehyde levels, and induced liver edema. No obvious changes in serum and liver tissue biochemical parameters were found and no significant pathological changes were detected in liver tissues after THP administration. Our results provide more information on the toxicity of THB and THP, and their related drug-drug interactions. (C) 2017 Elsevier B.V. All rights reserved.