الفهرس 
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Abstract
In the present investigation, new series of (Z)-3-(substituted) benzylidenechroman-2,4-diones (77-83),4-substituted piperazino/oxy/thio-3-(piperidin-1-ylmethyl)-2H-chromen-2-ones (97-103) 4-(3-substituted aminopropoxy)-2H-chromen-2-ones (113-117), chromeno[3,4-c]pyridines (136& 137), chromeno[4,3-d]pyrimidines (138&139), chromeno[4,3-c]pyrazole (140), N-aryl sulfonated coumarins (151-160) and (E)-3-substituted aminomethylene-2-thioxochroman-4-ones (173-176), aiming to obtain coumarins with antioxidant activity. All the newly synthesized compounds were subjected to in vitro antioxidant screening using bleomycin dependent DNA damage method. The results showed that most of the compounds exhibited different degrees of antioxidant activity. Compounds 77, 78, 79, 80, 101, 103, 113, 117, 138, 154, 157 and 175 are more active than ascorbic acid. We have expanded our investigations to study our synthesized ligands binding to CYP51-mtb, taking the advantage of applying structural biology techniques, we attempt to estimate the ligand affinity to a protein model suggesting that our ligands might act as a new anti-TB agents. Moreover an indepth computational theoretical study using quantum chemical calculations had been performed to study the coumarin ring ability to react with some free radicals (hydroxyl, hyDROPeroxo radical, and superoxide radical anion) by addition mechanism in gas phase and in presence of solvent (water). Different paths of reactions have been considered activation energies of all adducts suggest that these reactions should occur differently.