Discovery of soluble epoxide hydrolase inhibitors from Inula britannica: Inhibition kinetics, molecular dynamics...

Soluble epoxide hydrolase (sEH) is an enzyme involved in transforming epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids (DHETs). EETs play a pivotal role in maintaining anti-inflammatory response and pain regulation, making sEH as an important target for therapeutic interventions. Based on our present study of discovery of sEH inhibitors, herein, six new (1-6) and fifteen known compounds (7-21) with inhibitory effects toward sEH were isolated from Inula britannica. Among them, compounds 5 (inulabritanthymol G) and 9 (bellidtfolin) possessed strongest inhibitory abilities with IC₅₀ values of 3.87 and 2.85 μM, respectively. Inhibition kinetics indicated that they were assigned as uncompetitive inhibitors, and their K_i values were 1.93 and 1.89 μM, respectively. Molecular dynamics simulation demonstrated that the stability and interactions of inhibitors 5/9 with sEH were attributed to hydrogen bonds with amino acid residues of Asp335, Ser374, or Asn472. In addition, inhibitors 5 and 9 could exert anti-inflammatory effects through suppressing the NF-κB activation in LPS-exposed RAW264.7 cells, highlighting their potential as natural therapeutic agents for managing inflammatory diseases.