Soluble epoxide hydrolase inhibitory components from Rheum undulatum and in silico approach

Continuous efforts to identify sEH inhibitors using activity-guided fractionation have revealed 12 known compounds, 2–13, from Rheum undulatum. Compounds 2–13 and 1, which was obtained from the in-house library, were tested for inhibitory activity against sEH. Compounds 1–9, 11, and 12 were shown to have inhibitory activity, with IC₅₀ values ranging from 2.5 ± 0.5 to 53.2 ± 4.4 μM. They were subjected to enzyme kinetic studies to explore the binding mode between the ligand and receptor. Based on our results, compounds 1, 2, 5–9, and 11 (mixed type) and compounds 3 and 12 (noncompetitive type) had a preferred allosteric site. Compound 4 was identified as a competitive-type interaction in the active site. Molecular docking studies revealed the interacting residues and binding energy between sEH and inhibitors. Additionally, molecular dynamics provided detailed information on the interaction between the ligand and receptor.