Synthesis and Biological Assessment of Cyanopyridine-Based 1,3,4-Oxadiazole Derivatives: Anticancer Potential, Antioxidant Activity, Molecular Docking, and DFT Calculations

Abstract

A series of six novel cyanopyridine derivatives bearing a 1,3,4-oxadiazole ring have been synthesized and characterized by FTIR, ¹³C NMR, ¹H NMR, and elemental analysis. DFT calculations were carried out to determine their molecular geometries, electronic properties, and chemical reactivity. Their cytotoxicity has been evaluated against MCF-7 and CaCo-2 human cancer cell lines using the MTT assay. Most compounds displayed poor cytotoxic activity against the MCF-7 cell line except for compound 4e, which showed potent activity with IC₅₀ = 8.352 µM. However, the CaCo-2 cell line was highly sensitive toward most tested compounds with an IC₅₀ range from 2.612 µM to 8.394 µM except for compound 4 d. Molecular docking studies targeting human topoisomerase-IIβ revealed that all compounds exhibited excellent binding affinity within the enzyme's active site, with binding energies ranging from -7.33 to -8.28 kcal/mol. These findings suggest a potential anticancer mechanism underlying the observed cytotoxic activities. All tested compounds revealed low antioxidant activity in the DPPH assay. However, compounds 5b and 5 d presented moderate metal chelating activity. These findings underscore the potential anticancer properties of the synthesized cyanopyridine derivatives.

Keywords: 1,3,4‐oxadiazole; CaCo‐2; DFT calculations; MCF‐7; antioxidant activity; cyanopyridine; molecular docking.

FIGURE 1

Pharmaceutical drugs containing 1,3,4‐oxadiazole unit.

SCHEME 1

Synthetic pathway for compounds 1–4. Reagents and conditions: (I) Methyl bromoacetate, anhydrous K₂CO₃, DMF, room temperature (RT);(II) Hydrazine hydrate (100%), THF, reflux;(III) Triethyl orthoformate, 1,4‐dioxane, 5% PTSOH, reflux, argon atmosphere.

FIGURE 2

Cell viability outcomes and IC₅₀ (μM) values of compounds 4a‐f against CaCo2 and MCF‐7 cells following 48 h of drug treatment. Statistical significance is indicated by *p < 0.05.

FIGURE 3

Docking pose of compounds 4a‐f into the catalytic site of the human topoisomerase‐IIb enzyme complexed with DNA.

FIGURE 4

The most stable geometry of compounds 4a‐4f computed in the gas phase at B3LYP/6‐311 G + +(d,p) level.

FIGURE 5

Frontier molecular orbitals, LUMO (a) and HOMO (b), distribution and energies as well as molecular electrostatic potential maps (c) of compounds 4a‐4f.