Anemarsaponin BII inhibits the activity of CYP3A4, 2D6, and 2E1 with human liver microsomes

CONTEXT: Anemarsaponin BII is one of the most active saponins isolated from Anemarrhena asphodeloides Bunge (Asparagaceae), a commonly used Chinese traditional paediatric medicine. OBJECTIVE: This study investigates the effects of anemarsaponin BII on the activity of CYP450s to provide more guidance for the clinical use of anemarsaponin BII. MATERIALS AND METHODS: Using various diagnostic substrates, the effects of a fixed concentration of anemarsaponin BII (100 μM) on the activity of eight main isoforms of CYP450s (CYP1A2, 2A6, 3A4, 2C8, 2C9, 2C19, 2D6 and 2E1) was first studied with pooled human liver microsomes (HLMs). Then, dose-dependent (0, 2.5, 5, 10, 25, 50 and 100 μM anemarsaponin BII) and time-dependent (0, 5, 10, 15 and 30 min) experiments were performed to obtain corresponding kinetic parameters. RESULTS: Anemarsaponin BII showed significant inhibitory effects on the activity of CYP3A4, 2D6 and 2E1 with the IC(50) values of 13.67, 16.26 and 19.72 μM. Anemarsaponin BII acted as a non-competitive inhibitor of CYP3A4 with the K(I) value of 6.72 μM and competitive inhibitors of CYP2D6 and 2E1 with the K(I) values of 8.26 and 9.82 μM, respectively. Additionally, the inhibition of CYP3A4 was revealed to be time-dependent with the K(I) value of 4.88 μM and the K(inact) value of 0.053/min. CONCLUSIONS: The inhibitory effect of anemarsaponin BII on the activity of CYP3A4, 2D6 and 2E1 indicated the potential drug–drug interaction between anemarsaponin BII and drugs metabolized by these CYP450s. Further in vivo experiments are needed to validate the potential drug–drug interactions.