1. 8-methylene-tert-butylamine-3',5,7-trihydroxy-4'-methoxyflavanone (MTBH), a novel hesperidin derivative, has potential in the prevention of hepatic disease, however, its effects on cytochrome P450 isoforms (CYP450s) remains unexplored. The purpose was to investigate the effects of MTBH on the mRNA, protein levels, and activities of six CYP450s (1A2, 2C11/9, 2D2/6, 3A1/4, 2C13/19, and 2E1) in vitro and in vivo.2. In vitro study, rat and human liver microsomes were adopted to elucidate the inhibitory effect of MTBH on six CYP450s using probe drugs. In vivo study, Sprague-Dawley male rats were treated with MTBH (25, 50, or 100 mg/kg for 28 consecutive days), phenobarbital (80 mg/kg for 12 consecutive days), or 0.5% CMC-Na solution (control group) by intragastric administration, then, the mRNA, protein levels and activities of liver CYP450s were analysed by real-time PCR, western blotting and probe-drug incubation systems, respectively.3. The in vitro study indicated that MTBH inhibits the activities of CYP3A1/4 and CYP2E1 in rat and human liver microsomes. In vivo data showed that MTBH inhibits mRNA, protein levels, and activities of CYP3A1 and CYP2E1 in medium- and high-dose MTBH groups.4. MTBH has the potential to cause drug-drug interactions when co-administered with drugs that are metabolised by CYP3A1/4 and CYP2E1.