IC50 values of the ginsenosides and sapogenins against P450 enzymes.

Note:a. The percent inhibition of ginsenosides against the respective P450 enzymes is shown when its IC50 value is greater than the maximum concentration assayed.b. The maximum concentration of ginsenosides evaluated for their effects on CYP2C9 and CYP2D6 were 50 µM due to the marked solvent effect of 1% methanol on these two P450 enzymes (inhibition by 42.4% and 27.5%, respectively). When the final concentration of methanol was decreased to 0.5%, the solvent effects were acceptable for these two enzymes (10.1% and 18.9%, respectively). 1% methanol had no inhibition against CYP1A2 and CYP3A4 and had an acceptable inhibitory effect on CYP2C19 (9.7%).c. Positive control compounds were α-naphthoflavone (for CYP1A2), sulfaphenazole (CYP2C9), miconazole nitrate salt (CYP2C19), quinidine (CYP2D6), and ketoconazole (CYP3A4), respectively.d. A.A. = apparent activation. 100 µM 25-OH-PPD and 25-OH-PPT increased the turnover of Vivid® CYP3A4 red by more than 100%.