Inhibition of human cytochrome P450 enzymes by the natural hepatotoxin safrole

Food Chem Toxicol. 2005 May;43(5):707-12. doi: 10.1016/j.fct.2005.01.008.


The hepatotoxin, safrole is a methylenedioxy phenyl compound, found in sassafras oil and certain other essential oils. Recombinant cytochrome P450 (CYP, P450) and human liver microsomes were studied to investigate the selective inhibitory effects of safrole on human P450 enzymes and the mechanisms of action. Using Escherichia coli-expressed human P450, our results demonstrated that safrole was a non-selective inhibitor of CYP1A2, CYP2A6, CYP2D6, CYP2E1, and CYP3A4 in the IC(50) order CYP2E1 < CYP1A2 < CYP2A6 < CYP3A4 < CYP2D6. Safrole strongly inhibited CYP1A2, CYP2A6, and CYP2E1 activities with IC(50) values less than 20 microM. Safrole caused competitive, non-competitive, and non-competitive inhibition of CYP1A2, CYP2A6 and CYP2E1 activities, respectively. The inhibitor constants were in the order CYP1A2 < CYP2E1 < CYP2A6. In human liver microsomes, 50 microM safrole strongly inhibited 7-ethoxyresorufin O-deethylation, coumarin hydroxylation, and chlorzoxazone hydroxylation activities. These results revealed that safrole was a potent inhibitor of human CYP1A2, CYP2A6, and CYP2E1. With relatively less potency, CYP2D6 and CYP3A4 were also inhibited.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aryl Hydrocarbon Hydroxylases / antagonists & inhibitors
  • Cytochrome P-450 CYP1A2 Inhibitors
  • Cytochrome P-450 CYP2A6
  • Cytochrome P-450 CYP2D6 Inhibitors
  • Cytochrome P-450 CYP2E1 Inhibitors
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme Inhibitors*
  • Dose-Response Relationship, Drug
  • Escherichia coli / enzymology
  • Humans
  • Inhibitory Concentration 50
  • Kinetics
  • Liver / drug effects*
  • Liver / enzymology
  • Liver / metabolism
  • Microsomes, Liver / drug effects
  • Microsomes, Liver / enzymology*
  • Mixed Function Oxygenases / antagonists & inhibitors
  • Safrole / toxicity*


  • Cytochrome P-450 CYP1A2 Inhibitors
  • Cytochrome P-450 CYP2D6 Inhibitors
  • Cytochrome P-450 CYP2E1 Inhibitors
  • Cytochrome P-450 Enzyme Inhibitors
  • Mixed Function Oxygenases
  • Aryl Hydrocarbon Hydroxylases
  • CYP2A6 protein, human
  • CYP3A protein, human
  • Cytochrome P-450 CYP2A6
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • Safrole