title: Modifications of the ethanolamine head in N-palmitoylethanolamine: synthesis and evaluation of new agents interfering with the metabolism of anandamide.
abstract: The endogenous fatty acid amide anandamide (AEA) has, as a result of its actions on cannabinoid and vanilloid receptors, a number of important pharmacological properties including effects on nociception, memory processes, spasticity, and cell proliferation. Inhibition of the metabolism of AEA, catalyzed by fatty acid amide hydrolase (FAAH), potentiates the actions of AEA in vivo and therefore may be a useful target for drug development. In the present study, we have investigated whether substitution of the headgroup of the endogenous alternative FAAH substrate palmitoylethanolamide (PEA) can result in the identification of novel compounds preventing AEA metabolism. Thirty-seven derivatives of PEA were synthesized, with the C16 long chain of palmitic acid kept intact, and comprising 20 alkylated, 12 aromatic, and 4 halogenated amides. The ability of the PEA derivatives to inhibit FAAH-catalyzed hydrolysis of [(3)H]AEA was investigated using rat brain homogenates as a source of FAAH. Inhibition curves were analyzed to determine the potency of the inhibitable fraction (pI(50) values) and the maximal attained inhibition for the compound, given that solubility in an aqueous environment is a major issue for these compounds. In the alkylamide family, palmitoylethylamide and palmitoylallylamide were inhibitors of AEA metabolism with pI(50) values of 5.45 and 5.47, respectively. Halogenated derivatives (Cl and Br) exhibit pI(50) values of approximately 5.5 but rather low percentages of maximal inhibition. The -OH group of the ethyl head chain of N-palmitoylethanolamine was not necessary for interaction with FAAH. Amides containing aromatic moieties were less potent inhibitors of AEA metabolism. Compounds containing amide and ester bonds, 13 and 37, showed pI(50) values of 4.99 and 5.08, respectively. None of the compounds showed obvious affinity for CB(1) or CB(2) receptors expressed on Chinese hamster ovary (CHO) cells. It is concluded that although none of the compounds were dramatically more potent than PEA itself at reducing the metabolism of AEA, the lack of effect of the compounds at CB(1) and CB(2) receptors makes them useful templates for development of possible therapeutic FAAH inhibitors.
authors.affiliation: Unité de Chimie Pharmaceutique et de Radiopharmacie, Université Catholique de Louvain, Avenue Mounier, 73, UCL-CMFA 73.40, B-1200 Brussels, Belgium.
authors.forename: Séverine
authors.initials: S
authors.lastname: Vandevoorde
authors.forename: Kent-Olov
authors.initials: KO
authors.lastname: Jonsson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Fowler
authors.forename: Didier M
authors.initials: DM
authors.lastname: Lambert
mesh_terms: D000577:Amides; D000581:Amidohydrolases / Q000378:metabolism; D000818:Animals; D001095:Arachidonic Acids / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001921:Brain / Q000378:metabolism; D016466:CHO Cells; D002186:Cannabinoids / Q000378:metabolism; D006224:Cricetinae; D063388:Endocannabinoids; D004983:Ethanolamines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D010169:Palmitic Acids / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D011869:Radioligand Assay; D051381:Rats; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000037:antagonists & inhibitors; D013329:Structure-Activity Relationship; D000099252:Fatty Acid Amide Hydrolases
chemical_list: D000577:Amides; D000581:Amidohydrolases; D001095:Arachidonic Acids; D002186:Cannabinoids; D063388:Endocannabinoids; D004983:Ethanolamines; D010169:Palmitic Acids; D053284:Polyunsaturated Alkamides; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D000099252:Fatty Acid Amide Hydrolases; C469526:Cnr2 protein, rat; C005958:palmidrol; C078814:anandamide