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Antioxidants are small organic molecules which have important role of maintaining healthy balance between reactive oxygen species and antioxidants by scavenging free radicals. It is well known that overproduction of ROS is linked to oxidative stress which is important factor in the development of many diseases and disorders. Many of naturally occurring and synthetic coumarines were vastly studied for their biological activities including antioxidant capacity.[1] On the other hand, the biological activity of imidazo[4, 5-b]pyridine is still unexplored. As acrylonitrile derivatives of imidazo[4, 5-b]pyridine showed promising antioxidative potential, series of iminocoumarine derivatives was logical next step in development of compounds with more pronounced antioxidative activity.[2] This work presents the synthesis, structural characterization and antioxidative activity of 6-substituted iminocoumarin derivatives of imidazo[4, 5-b]pyridine. For the synthesis of novel targeted compounds, classical reactions as well as microwave assisted synthesis were used. Main precursors were prepared by the uncatalyzed microwave amination starting from halogeno-substituted precursors followed by the reduction of nitro moiety to amino. 2-cyanomethlyimidazo[4, 5-b]pyridines obtained in the cyclocondensation reaction with ethyl cyanoacetate, while targeted iminocoumarins were prepared in condensation reaction with 5-substituted salicylaldehydes. Additionally, amino-substituted derivatives were prepared by the reduction with SnCl2×2H2O which were further protonated to obtain their hydrochloride salts. The structures of newly prepared compounds were confirmed by means of 1H and 13C NMR spectroscopy as well as MS spectrometry. Newly prepared compounds were tested for their antioxidative activity in vitro by using several spectroscopic methods such as ABTS, DPPH and FRAP. Measured antioxidative capacities will be rationalized by computational analysis. |
