Schisandrin A

Schisandrin A inhibits CYP3A activity with an IC₅₀ of 6.60 μM and K_i of 5.83 μM, respectively. IC50 & Target:IC50: 6.60 μM (CYP3A)^[1]
Ki: 5.83 μM (CYP3A)^[1] In Vitro: Schisandrin A (Sch A) strongly inhibits microsomal midazolam 1-hydroxylation catalyzed by CYP3A, with an IC₅₀ of 6.60 μM. The recovery of enzyme activity in the absence or presence of Schisandrin A is shown in dilution assay plots. The K_i value for Schisandrin A is obtained from the Dixon plots and is 5.83 μM. The inactivation of rat liver microsomal midazolam 1-hydroxylation activity by Schisandrin A in the presence of NADPH is found to be time- and concentration-dependent. The K_inact and K_i are estimated to be 0.134/min and 4.51 μM, respectively for Schisandrin A^[1]. In Vivo: Schisandrin A (SchA) significantly inhibits CYP3A activity in rat hepatic microsomes and V_max value of each group in a concentration-dependent manner. The double-reciprocal plots and the secondary plot show that Schisandrin A inhibits CYP3A activity, with an apparent K_i value of 30.67 mg/kg. In each Schisandrin A-treated group, Schisandrin A also significantly decreases 1-hydroxymidazolam plasma concentrations compared with the negative group (to levels similar to the positive group)^[2].