Enzyme activities of microsomal P450 enzymes
Inhibition by silybin expressed as IC50 or Ki ± S.E.M.
P450 Enzyme | Substrate | Km | Substrate Conc. | Silybin IC50 | Silybin Ki | |
|---|---|---|---|---|---|---|
| μM | ||||||
| CYP1A2 | Ethoxyresorufin | 2.4 | 2.5 | 220 ± 31 | 165 ± 28 | |
| CYP2A6 | Coumarin | 8.2 | 10 | N.A. | N.A. | |
| CYP2B6 | 7-Ethoxy-4-(trifluoromethyl)coumarin | 14.1 | 15 | N.A. | N.A. | |
| CYP2C8 | Luciferin-methyl ester | N.D. | 150 | ≥250 | N.A. | |
| CYP2C9 | Diclofenac | 15.9 | 16 | 34.1 ± 11 | 75 ± 12 | |
| CYP2C19 | S-Mephenytoin | 81.0 | 80 | N.A. | N.A. | |
| CYP2D6 | Bufuralol | 25.3 | 25 | ≥250 | N.A. | |
| CYP2E1 | Chlorzoxazone | 52.0 | 50 | N.A. | N.A. | |
| CYP3A4 | Testosterone | 77.5 | 100 | 49.8 ± 14 | 21 ± 6 | |
N.A., not accessible; N.D., not determined.