Abstract
1.This study investigated the mechanism underlying Echinacea-mediated induction of CYP1A2, CYP3A4 and MDR1 in terms of human pregnane X receptor (PXR) activation. 2.Crude extracts and fractions of Echinacea purpurea were tested for PXR activation in HepG2 cells by a reporter gene assay. Quantitative real-time PCR was carried out to determine their effects on CYP1A2 and CYP3A4 mRNA expressions. Capsules and fractions were risk ranked as high, intermediate and remote risk of drug-metabolizing enzymes induction based on EC50 values determined for respective CYPs. 3. Fractions F1, F2 and capsule (2660) strongly activated PXR with 5-, 4- and 3.5-fold increase in activity, respectively. Echinacea preparations potentiated up-regulation of CYP1A2, CYP3A4 and MDR1 via PXR activation. 4.Thus E. purpurea preparations cause herb-drug interaction by up-regulating CYP1A2, CYP3A4 and P-gp via PXR activation.