Synthesis, QSAR Model Study and Antimicrobial Evaluation of Esters and Thioester Derivatives of Isonicotinic Acid on the Different Strains of Mycobacterium Tuberculosis

Isoniazid is one of the widely used first-line drugs in the treatment of tuberculosis for many years but the mechanism of the action of the drugs is still not clear. Herein, we report the synthesis, QSAR model study and biological effects of esters and thioester derivative of isonicotinic acid (INA) on different strains of Mycobacterium tuberculosis in an attempt to establish the mode of action of the active form of Isoniazid (INH). The esters of INA are expected to show antibiotic activities against strains of Mycobacterium tuberculosis upon activation by intracellular nonspecific esterases, while thioesters is expected not to show antimicrobial effects and thus served as control. The obtained results indicated that the synthesized esters did not show antimicrobial activity. The conclusion drawn from the result is that either INA is not the active form of INH or that the esters show poor water solubilityin addition to the possibility of acquired during resistance of the strains during culture and testing all of which could hamper mycobacterial cell up take. This suggests that more studies are needed to search for the possible active form of isoniazid.