Synthesis, Antioxidant and Anti-Inflammatory Activities of Ethyl 2-(2-Cyano-3- (Substituted Phenyl)acrylamido)-4,5-Dimethylthiophene-3-Carboxylates

Abstract

Objective: Objective of the study was to synthesize and evaluate a series of novel compounds, ethyl 2-(2-cyano-3-(substituted phenyl)acrylamido)-4,5-dimethylthiophene-3-carboxylates, for in vitro antioxidant and in vivo anti-inflammatory activities.Methods: Ethyl 2-(2-cyano-3-(substituted phenyl)acrylamido)-4,5-dimethylthiophene-3-carboxylates were synthesized by knoevenagel condensation of active methylene group of ethyl 2-(2-cyanoacetamido)-4,5-dimethylthiophene-3-carboxylate with substituted benzaldehydes. The synthesized compounds were evaluated for their in vitro antioxidant properties in three different models, viz., reduction of 1,1-diphenyl-2-pycrylhydrazyl free radical, scavenging of nitric oxide free radical, and ferric ion-induced lipid peroxidation using rat brain homogenate. Few selected compounds with good antioxidant properties were pharmacologically evaluated for anti-inflammatory activity by carrageenan-induced rat paw edema model. Results:Clean and efficient synthetic procedure was used for the preparation of series of compounds. The structures of synthesized compounds were confirmed by infrared, 1 H nuclear magnetic resonance and mass spectra. The antioxidant activity data revealed that the compounds of ethyl 2-(2-cyano-3-(substituted phenyl)acrylamido)-4,5-dimethylthiophene-3-carboxylate containing phenolic substitution showed greater antioxidant activity. Hence, the active compounds were evaluated for anti-inflammatory activity and found to possess good activity. The percentage inhibition of rat paw edema obtained for the evaluated compounds was in the range of 70.2-83.1, comparable to the standard drug diclofenac (85.0%). Conclusion:The use of inexpensive, eco-friendly and readily available reagents, easy work-up and high purity of products makes the procedure a convenient and robust method for the synthesis of title compounds. The compounds of ethyl 2-(2-cyano-3-(substituted phenyl)acrylamido)-4,5-dimethylthiophene-3-carboxylate containing phenolic substitution showed greater antioxidant and anti-inflammatory activities.