Inhibition Potential of Cycloartane-Type Glycosides from the Roots of Cimicifuga dahurica against Soluble Epoxide Hydrolase

A phytochemical assay-guided fractionation of the 95% ethanol extract of Cimicifuga dahurica roots afforded 29 9,19-cycloartane triterpenoid glycosides, including the new cimiricasides AF (1-6). The structures of 1-6 were established using contemporary NMR methods and from the HRESIMS data, and the sugar moiety in each case was confirmed by acid hydrolysis and subsequent GC/MS analysis. Compounds 2, 4, 5, 79, 18, 25, and 29 showed soluble epoxide hydrolase inhibitory effects with IC50 values of 0.4 +/- 0.1 to 24.0 +/- 0.2 mu M. The compounds were analyzed by enzyme kinetic studies to explore the binding mode between the ligand and receptor. Compounds 4 (mixed type), 8, 18, and 29 (noncompetitive type) bound to a preferred allosteric site, while compounds 2, 5, 7, 9, and 25 had competitive interactions at the active site. The binding mechanism of selected inhibitors was investigated using molecular docking and dynamics simulations.