A series of novel 4,5-diarylthiophene-2-carboxamide containing alkyl, cycloalkyl, aryl, aryl alkyl and heterocyclic alkyl moieties were synthesized, characterized and subsequently evaluated for antiinflammatory property. Among the novel compounds, the inhibition of bovine serum albumin denaturation assay revealed that the aryl and aryl alkyl derivatives of 4,5-diarylthiophene-2-carboxamide showed antiinflammatory activity comparable to the standard drug diclofenac sodium whereas alkyl and cycloalkyl amide derivatives showed less activity. Docking studies with these compounds against cyclooxygenase-2 receptor(PDB 1D: 1PXX) indicated that they exhibit specific interactions with key residues located in the site of the COX2 structure, which corroborates the hypothesis that these molecules are potential ligands of COX2. The analysis of the docking results, which takes into account the hydrophilic and hydrophobic interactions betweenthe ligands and the target, identified N-(4-bromophenyl)-4,5-bis(4 hydroxyphenyl)thiophene-2-carboxamide (6k) having high binding free energy of −11.67 kcal/mole (comparable with standard diclofenac sodium) and the best docking score, indicating effective binding of the compound 6k at the active site.

In our earlier studies, we have shown that the introduction of amino moieties at carboxylic acid of 4,5-diarylthiophene-2-carboxylic acid significantly improved the anti-inflammatory activity of the compound against the standard drug diclofenac sodium. In the present study, we have synthesized new derivatives of 4,5- diarylthiophene-2-carboxylic acid by modifying the hydroxyl group of the phenyl ring and carboxylic acid group of the thiophene ring.Aseries of novel 4,5-diarylthiophene-2-carboxylic acid derivatives containing bis-allyloxyand hydroxypropoxy with methyl or ethyl ester moieties were synthesized, characterized and subsequently evaluated for anti-inflammatory and antioxidant property. Among the novel compounds, the inhibition of bovineserum albumin denaturation assay revealed that the compound 4,5-bis(4-(3-hydroxypropoxy)phenyl)thiophene- 2-carboxylic acid (15) and ethyl ester (13) having anti-inflammatory activity better than the standard drugdiclofenac sodium. The antioxidant screening showing 4,5-bis(4-(allyloxy)phenyl)thiophene-2-carboxylic acid (10), 4,5-bis(4-(3-hydroxypropoxy)phenyl)thiophene-2-carboxylic acid methyl ester (11) and 4,5-bis(4-(3- hydroxypropoxy)phenyl)thiophene-2-carboxylic acid ethyl ester (13) exhibited a slightly moderate antioxidant activity than standard ascorbic acid. Molecular docking analysis was performed for the synthesized compounds with the cyclooxygenase-2 (COX-2) receptor (PDB 1D: 1PXX). Docking studies revealed that all the synthesised compounds exhibit greater binding affinity than the standard drug. Particularly, the compound ethyl 4,5-bis(4- (allyloxy)phenyl)thiophene-2-carboxylate (8) and allyl 4,5-bis(4-(allyloxy)phenyl)thiophene-2-carboxylate (9) having high free energy binding of −10.40 and −10.48 Kcal/mol, respectively.