Rapid screening of commercially available herbal products for the inhibition of major human hepatic cytochrome P450 enzymes using the N-in-one cocktail

Self-administration of complementary products concurrently with conventional medication is increasingly common. The potential for cytochrome P450 (CYP) inhibition requires investigation. The N-in-one assay with ten probe substrates for nine CYPs was used with human liver microsomes to investigate ten products. CYP inhibition was measured in a single liquid chromatography-tandem mass spectrometry (LC/MS-MS) analysis. Estimated IC50-values were determined for the extracts that produced significant inhibition (less than 100 μg ml−1).Inhibition of CYP2C19 by dong quai (IC50 = 13.7–14.3 μg ml−1 for the methanolic extract) and CYP2D6 by goldenseal (IC50 = 6.7 and 6.3 μg ml−1 for the aqueous and methanolic extracts, respectively), are of particular concern as the potential for adverse interactions is high. The inhibition of CYP2C8 by horsetail (IC50 = 93 μg ml−1 for the aqueous extract) requires further investigation, as the potential for concurrent use with products that require CYP2C8 for metabolism is signifi...