The effect of St John's wort (hypericum perforatum) on cytochrome p450 1a2 activity in perfused rat liver

Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2011 Sep;155(3):253-7. doi: 10.5507/bp.2011.047.


Aims: We previously reported the effect of St John's wort (Hypericum perforatum) standardised extract LI 160 on the activities of cytochrome P450 2C6, 2D2 and 3As (Dostalek et al., Life Sciences 2005;78(3):239-44). In this study, we aimed to assess the effect of St John's wort on the activity of cytochrome P450 1A2.

Methods: The isolated perfused rat liver model was used in our experiments with phenacetin as a marker substrate for cytochrome P450 1A2. Male Wistar rats were treated with St John's wort extract (100 mg/kg, once daily for 10 days); comparative inhibitor (alpha-naphthoflavone, 100 mg/kg) or comparative inducer (omeprazole, 30 mg/kg).

Results: The rate of formation of acetaminophen was significantly inhibited by the use of St John's wort (P<0.001). In addition, St John's wort extract inhibited cytochrome P450 1A2 activity significantly more than the control inhibitor (P<0.001).

Conclusions: St John's wort significantly inhibited cytochrome P450 1A2 enzyme activity. It remains to be determined whether the co-administration of St John's wort extract and other medications or substrates for cytochrome P450 1A2 could result in significant drug interactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzoflavones / pharmacology
  • Cytochrome P-450 CYP1A2 / metabolism*
  • Cytochrome P-450 CYP1A2 Inhibitors
  • Enzyme Inhibitors / pharmacology
  • Hypericum*
  • In Vitro Techniques
  • Liver / enzymology*
  • Male
  • Omeprazole / pharmacology
  • Plant Extracts / pharmacology*
  • Rats
  • Rats, Wistar


  • Benzoflavones
  • Cytochrome P-450 CYP1A2 Inhibitors
  • Enzyme Inhibitors
  • Plant Extracts
  • alpha-naphthoflavone
  • Cytochrome P-450 CYP1A2
  • Omeprazole