Convergent Synthesis, Kinetics, and Computational Studies of Indole(phenyl)triazole Bi-Heterocycles Modified with Propanamides as Elastase Inhibitors

Biological screening combined with the synthesis of heterocyclic compounds with numerous functions is the most effective approach available for pharmacological assessment. In the  under taken research that is presented here,  4-(1H-indol-3-yl)butanoic acid was sequentially converted into 4-(1H-indol-3-yl)butanoate, 4-(1H-indol-3-yl)butanohydrazide and 5-[3-(1H-indol-3-yl)propyl]-1,2,4-triazole-2-thiol  as a nucleophile. The structural confirmation of all the synthesized compounds was done by IR, 1H-NMR, 13C-NMR and CHN analysis data. The enzyme inhibitory effects of these bi-heterocyclic propanamides were evaluated against elastase, and Oleanolic acid with IC50 value 13.453 ± 0.015 µM was used as a standard.  The kinetics mechanism was ascribed by Lineweaver-Burk plots, which revealed that compound 9d inhibited elastase competitively. The inhibition constant Ki calculated from Dixon plots for this compound was 0.51 μM. Compound 9d's activity (IC50 = 0.142 ± 0.014 µM) significantly increased when a slightly bulky ethyl group was replaced for the solitary methyl group in 9c at the para position. However, compound 9e's activity was significantly lower (IC50 = 38.338 ± 0.993µM). These molecules also exhibited mild cytotoxicity. So, these molecules might be deliberated as nontoxic medicinal scaffolds for dealing with the elastase related ailments such as lungs diseases, cyclic neutropenia, pruritic skin disease and liver infection.