title: Synthesis and biological evaluation of 3,4-diphenyl-1,2,5-oxadiazole-2-oxides and 3,4-diphenyl-1,2,5-oxadiazoles as potential hybrid COX-2 inhibitor/nitric oxide donor agents.
abstract: A group of 3,4-diphenyl-1,2,5-oxadiazole-2-oxides (3,4-diphenylfuroxans) and the corresponding N-desoxy 3,4-diphenyl-1,2,5-oxadiazoles (3,4-diphenylfurazans) analogs, were synthesized for in vitro evaluation as hybrid cyclooxygenase (COX) inhibitor/nitric oxide donor agents. Reaction of 1-[4-(methylsulfonyl)phenyl]-2-phenylethene with an aqueous sodium nitrite solution in acetic acid afforded a mixture (3:1 ratio) of the inseparable 4-[4-(methylsulfonyl)phenyl]-3-phenyl-1,2,5-oxadiazole-2-oxide (13a) and 3-[4-(methylsulfonyl)phenyl]-4-phenyl-1,2,5-oxadiazole-2-oxide (13b) regioisomers. A group of related regioisomers possessing either a p-aminosulfonylphenyl (16) or a p-azidosulfonylphenyl (17), moiety were obtained by chlorosulfonation of the unsubstituted 3,4-diphenylfuroxan (10) and subsequent reaction with either ammonium hydroxide or sodium azide, respectively. The methanesulfonyl regioisomers 13a,b [COX-1 IC50=11.6 microM; COX-2 IC50=0.12 microM; COX-2 selectivity index (SI)=97] and aminosulfonyl regioisomers 16 (COX-1 IC50=9.8 microM; COX-2 IC50=0.78 microM; COX-2 SI=12), like the reference drug celecoxib (COX-1 IC50=33.1 microM; COX-2 IC50=0.07 microM; COX-2 SI=472), were potent in vitro COX-2 inhibitors with a good COX-2 selectivity index. Release of nitric oxide (NO) from the 3,4-diphenylfuroxan compounds (10, 13a,b, 16, 17) was thiol-dependent since the % NO released was higher upon incubation in the presence of l-cysteine (0.57-3.18%) compared to that in phosphate buffer solution at pH7.4 (0.06-0.15%). Molecular modeling (docking) studies show that the methanesulfonyl (MeSO2) COX-2 pharmacophore present in regioisomers 13a,b is positioned in the vicinity of the COX-2 secondary pocket. The in vitro NO release data, COX-1/COX-2 inhibition and COX-2 SI structure-activity relationships acquired, and molecular modeling docking studies suggest that the 1,2,5-oxadiazole-2-oxide (furoxan) ring possesses beneficial features that should be present in a suitable central ring template (bioisostere) pertinent to the design novel hybrid COX-2 inhibitor/nitric oxide donor agents with a low ulcerogenicity profile that may be free from adverse cardiovascular effects.
authors.affiliation: Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2N8.
authors.forename: Carlos
authors.initials: C
authors.lastname: Velázquez
authors.forename: P N Praveen
authors.initials: PN
authors.lastname: Rao
authors.forename: Robert
authors.initials: R
authors.lastname: McDonald
authors.forename: Edward E
authors.initials: EE
authors.lastname: Knaus
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology; D008958:Models, Molecular; D015394:Molecular Structure; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000138:chemical synthesis* / Q000494:pharmacology; D010069:Oxadiazoles / Q000138:chemical synthesis* / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000378:metabolism; D012756:Sheep; D013329:Structure-Activity Relationship
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D009569:Nitric Oxide; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases