Inhibition of UDP-Glucuronosyltransferases (UGTs) Activity by constituents of Schisandra chinensis

Structure-activity relationship for the inhibition of Schisandra chinensis's ingredients toward (Uridine-Diphosphate) UDP-glucuronosyltransferases (UGTs) activity was performed in the present study. In vitro incubation system was employed to screen the inhibition capability of S. chinensis's ingredients, and in silico molecular docking method was carried out to explain possible mechanisms. At 100 μM of compounds, the activity of UGTs was inhibited by less than 90% by schisandrol A, schisandrol B, schisandrin, schisandrin C, schisantherin A, gomisin D, and gomisin G. Schisandrin A exerted strong inhibition toward UGT1A1 and UGT1A3, with the residual activity to be 7.9% and 0% of control activity. Schisanhenol exhibited strong inhibition toward UGT2B7, with the residual activity to be 7.9% of control activity. Gomisin J of 100 μM inhibited 91.8% and 93.1% of activity of UGT1A1 and UGT1A9, respectively. Molecular docking prediction indicated different hydrogen bonds interaction resulted in the different inhibition potential induced by subtle structure alteration among schisandrin A, schisandrin, and schisandrin C toward UGT1A1 and UGT1A3: schisandrin A > schisandrin > schisandrin C. The detailed inhibition kinetic evaluation showed the strong inhibition of gomisin J toward UGT1A9 with the inhibition kinetic parameter (Ki ) to be 0.7 μM. Based on the concentrations of gomisin J in the plasma of the rats given with S. chinensis, high herb-drug interaction existed between S. chinensis and drugs mainly undergoing UGT1A9-mediated metabolism. In conclusion, in silico-in vitro method was used to give the inhibition information and possible inhibition mechanism for S. chinensis's components toward UGTs, which guide the clinical application of S. chinensis.