Effect of silybin on the P450 3A4 BFC O-debenzylation activity, reduced CO spectrum, and heme remaining Assay conditions were as described under Materials and Methods. The data shown represent the mean and standard deviations from three experiments.
Incubation Conditions | Activity Remaining | P450 Remaininga | Heme Remaining (HPLC)b | Heme Remaining (Pyridine Hemochrome)c | |
|---|---|---|---|---|---|
| % of control | |||||
| +Silybin, -NADPH | 71 ± 2 | 107 ± 6 | 102 ± 4 | N.D. | |
| +Silybin, +NADPH | 38 ± 3 | 46 ± 6 | 62 ± 3 | 57 ± 7 | |
N.D., not determined.
↵ a P450 remaining was determined from the reduced CO binding spectrum. The control sample value was set to 100%. The 100% values for activity, P450, and heme by HPLC and pyridine hemochrome were 1.7 ± 5 nmol/nmol/min, 88 ± 1.1 pmol, 100 pmol, and 167 ± 10 pmol, respectively
↵ b The amount of heme remaining was calculated after integrating the area under the heme peak at 405 nm from the HPLC elution profile. The area obtained for the control sample was set to 100%
↵ c The pyridine hemochrome spectrum was obtained as described by using the method of Koop (1990)