Design, synthesis and in vitro study of 5,6-diaryl-1,2,4-triazine-3-ylthioacetate derivatives as COX-2 and β-amyloid aggregation inhibitors.

In order to find novel cyclooxygenase (COX)-2 inhibitors for treating inflammatory-based diseases such as Alzheimer's disease (AD), an ethyl carboxylate side chain was added to 5-(4-chlorophenyl)-6-(4-(methylsulfonyl)phenyl)-3-(methylthio)-1,2,4-triazine (lead compound II) to maintain residual inhibition of COX-1 through interacting with Arg120. A preliminary molecular docking study on both the COX-1/COX-2 active sites truly confirmed our hypothesis. Accordingly, a series of ethyl 5,6-diaryl-1,2,4-triazine-3-ylthioacetate derivatives were synthesized and their chemical structures were confirmed by NMR, IR and MS spectra. Further in vitro COX-1/COX-2 evaluations revealed that compound 6c (COX-2 IC50  = 10.1 μM, COX-1 IC50  = 88.8 μM) is the most selective COX-2 inhibitor while maintaining residual inhibition of COX-1. In order to evaluate their potential use against AD, an in vitro evaluation of β-amyloid fibril formation was performed. The results indicated that the prototype compounds 6 are effective β-amyloid destabilizing agents while compound 6c could inhibit 94% of the β-amyloid fibril formation after 48 h. Finally, the in silico assessment results of their blood-brain barrier permeability were satisfactory.
(© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)