Dihydrofolate reductase inhibitory potential of 1H-indole-based-meldrum linked 1H-1,2,3-triazoles as new anticancer derivatives: In-vitro and in-silico studies

In this present work, we describe the syntheses of a new series of 32 1H-indole-based-meldrum linked 1H-1,2,3-triazole derivatives (2-13, 15a-15f, 16a-16f, 17a-17f and 19a, 19b, 20a), which constitute a new class of 1H-1,2,3-triazoles. Compounds 15a-15f, 16a-16f, 17a-17f have been prepared by employing "click" reactions between substituted 1H-indole-based meldrum alkynes (11, 12 and 13) and substituted aromatic azides (14a-14f) in the presence of copper iodide (CuI) and Hünig's base. Then, the synthesis of compounds 19, 20 through decomposition of meldrum moiety. The resulting compounds have been screened for their dihydrofolate reductase (DHFR) inhibition activity. All the newly synthesized compounds were characterized by ¹H NMR, ¹³C NMR, ¹⁹F NMR (spectroscopy when applicable), and HR-ESI-MS spectroscopy techniques. The X-ray crystallography studies have unambiguously confirmed the structure of compounds 6, 11 and 13. Furthermore, their DHFR-inhibitory activity was evaluated in-vitro. The results obtained from the DHFR-inhibitory assay revealed that all the synthesized 1H-indole-based-meldrum linked 1H-1,2,3-triazole derivatives were highly potent inhibitors, with IC₅₀ values in the range 3.48 ± 0.16-30.37 ± 1.20 μM. Ten compounds (15c-15f, 16c-16f, 17e and 17f) among the 32 synthesized 1H-indole-based-meldrum linked 1H-1,2,3-triazole compounds were found to exhibit exceptional inhibitory while the rest of the derivatives showed moderate activities. Additionally, molecular docking analysis of the most active (16f), moderate (15c) and least active (16a) inhibitors reflect excellent binding of 16f with the binding residues of DHFR with higher docking score (-9.13 kcal/mol) than that of 15c and 16a. The docking analysis correlates well with the inhibitory potential of these synthesized molecules. Overall, this study may pave the way to medicinal analogues of 1H-indole-based-meldrum linked 1H-1,2,3-triazoles as potent DHFR inhibition activity.