Pharmacophoric model building for antitubercular activity of the individual Schiff bases of small combinatorial library

Abstract

Synthesis and evaluation of anti-TB activity of individual compounds of Schiff bases combinatorial library were done against Mycobacterium tuberculosis H 37Rv at a single concentration of 6.25 μg/mL according to the protocol of TAACF. Compounds 2C and 3D produced 99% inhibitory activity on the investigated organism, while the other tested compounds showed lower activity ranging from 35 to 84%. It was found that there are no relation between the anti-TB activity of the tested compounds and their lipophilicity expressed by C log P of these compounds. A 3D pharmacophoric model has been generated by Molecular Operating Environment (MOE) using a training set of 10 reported anti-TB compounds and testing the synthesized compounds ( 1A, 1B, 1D, 1E, 2C, 3A, 3C, 3D, 3E and 4A– 4E). The generated pharmacophoric features include, F1: hydrogen bond donors (Don), F2: aromatic rings (Aro), F3: hydrogen bond acceptors (Acc)/metal ligator (ML), F4: Aro/hydrophobic (Hyd). In all hit set, it was found that the amidic nitrogen CONH–N C fitted the region of the Don, F1, while the amidic carbonyl group fitted the region of the Acc/ML, F3. The distances bridging F1 to F2, F3 and F4 were essential for anti-TB activity in the developed pharmacophore model, as it was confirmed from model validation procedure.