Table 2

Inhibition constants for St. John's wort constituents on human cytochrome P450 activities

St. John's Wort ConstituentCYP EnzymeKi2-aMode of Inhibition
μM
HyperforinCYP2C91.8  ± 0.9Competitive
CYP2D61.5  ± 0.9Noncompetitive
CYP3A40.49  ± 0.24Competitive
I3,II8-BiapigeninCYP1A20.95  ± 0.22Competitive
CYP2C90.32  ± 0.14Competitive
CYP2D62.3  ± 1.8Competitive
CYP3A40.038  ± 0.006Competitive
HypericinCYP2C91.4  ± 1.1Competitive
CYP2D62.6  ± 0.9Competitive
CYP3A44.2  ± 2.2Competitive
QuercetinCYP1A23.3  ± 0.6Noncompetitive
  • 2-a Values are mean ± S.D.