Three novel series of diaryl heterocyclic derivatives bearing the 2-oxo-5H-furan, 2-oxo-3H-1,3-oxazole, and 1H-pyrazole moieties as the central heterocyclic ring were synthesized and their in vitro inhibitory activities on COX-1 and COX-2 isoforms were evaluated using a purified enzyme assay. The 2-oxo-5H-furan derivative 6b was identified as potent COX inhibitor with selectivity toward COX-1 (COX-1 IC(50)=0.061 microM and COX-2 IC(50)=0.325 microM; selectivity index (SI)=0.19). Among the 1H-pyrazole derivatives, 11b was found to be a potent COX-2 inhibitor, about 38 times more potent than Rofecoxib (COX-2 IC(50)=0.011 microM and 0.398 microM, respectively), but showed no selectivity for COX-2 isoform. Compound 11c demonstrated strong and selective COX-2 inhibitory activity (COX-1 IC(50)=1 microM, COX-2 IC(50)=0.011 microM; SI= approximately 92). Molecular docking studies of compounds 6b and 11b-d into the binding sites of COX-1 and COX-2 allowed to shed light on the binding mode of these novel COX inhibitors.
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