Inhibition of human CYP enzymes by St. John's wort constituents
| Inhibitor | IC50 | ||||
|---|---|---|---|---|---|
| CYP1A2 PhenacetinO-Deethylase | CYP2C9 Diclofenac 4-Hydroxylase | CYP2C19 S-Mephenytoin 4-Hydroxylase | CYP2D6 Bufuralol 1′-Hydroxylase | CYP3A4 Testosterone 6β-Hydroxylase | |
| μM | |||||
| Hyperforin | >100 | 4.4 | 31 | 1.6 | 2.3 |
| I3,II8-Biapigenin | 3.7 | 4.0 | 28 | 5.7 | 0.082 |
| Quercetin | 7.5 | 47 | >100 | 24 | 22 |
| Chlorogenic acid | >100 | >100 | N.D.1-a | >100 | >100 |
| Hypericin | >100 | 3.4 | 37 | 8.5 | 8.7 |
Substrate concentrations used were as follows: phenacetin (50 μM), diclofenac (10 μM), S-mephenytoin (50 μM), bufuralol (10 μM), and testosterone (50 μM).
↵1-a At concentrations ≥30 μM, chlorogenic acid caused an HPLC-MS interference in the 4-hydroxymephenytoin assay. Hence, the IC50 could not be determined for this compound on CYP2C19 activity (N.D.).