Potent Natural Soluble Epoxide Hydrolase Inhibitors from Pentadiplandra brazzeana Baillon: Synthesis, Quantification, and Measurement of Biological Activities In Vitro and In Vivo

Seiya Kitamura,Maximilienne Nyegue,Christophe Morisseau,Bruce D Hammock,Gina R De Nicola,Shizuo G Kamita,Bora Inceoglu,Monika Oberer

doi:10.1371/journal.pone.0117438

Abstract

We describe here three urea-based soluble epoxide hydrolase (sEH) inhibitors from the root of the plant Pentadiplandra brazzeana. The concentration of these ureas in the root was quantified by LC-MS/MS, showing that 1, 3-bis (4-methoxybenzyl) urea (MMU) is the most abundant (42.3 μg/g dry root weight). All of the ureas were chemically synthesized, and their inhibitory activity toward recombinant human and recombinant rat sEH was measured. The most potent compound, MMU, showed an IC50 of 92 nM via fluorescent assay and a Ki of 54 nM via radioactivity-based assay on human sEH. MMU effectively reduced inflammatory pain in a rat nociceptive pain assay. These compounds are among the most potent sEH inhibitors derived from natural sources. Moreover, inhibition of sEH by these compounds may mechanistically explain some of the therapeutic effects of P. brazzeana.

Highlights

Soluble epoxide hydrolase is the major enzyme responsible for the hydrolysis of epoxy fatty acids (EpFAs) to their corresponding vicinal diols in humans and other mammals [1]
The crude root extract of P. brazzeana was prepared by percolation in DCM-methanol (1:1), and the inhibitory activity of the extract toward human soluble epoxide hydrolase (sEH) was measured by both fluorescent assay (CMNPC assay) and radioactivity based assay (t-DPPO assay) [30,31]
We demonstrate that urea compounds found in the root of P. brazzeana have potent sEH inhibitory activities

Summary

Introduction

Soluble epoxide hydrolase (sEH, EC 3.3.2.10) is the major enzyme responsible for the hydrolysis of epoxy fatty acids (EpFAs) to their corresponding vicinal diols in humans and other mammals [1]. These EpFAs include the epoxides of linoleic, arachidonic, eicosapentaenoic, and docosahexaenoic acid that are produced primarily by cytochrome P450s. These natural molecules are pleiotropic endogenous mediators with key functions in inflammation [1], pain [2], and blood pressure regulation [3]. SEH inhibitors were shown to be PLOS ONE | DOI:10.1371/journal.pone.0117438 February 6, 2015

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