Conformational Dynamics, Isomerization, and Biological Activity of Acridine-Thiazolidinone Hybrids: A Combined Experimental and Theoretical Study

A new series of acridin-4-yl–based
thiazolidinone derivatives
was synthesized and structurally characterized using NMR, IR, HRMS,
and single-crystal X-ray diffraction. NMR analysis in solution revealed
signal multiplicity suggestive of isomeric or conformational heterogeneity.
To investigate this behavior, we employed GFN2-xTB, DFT (PBE0-D4 and
revDSD-PBEP86-D4), and ab initio molecular dynamics simulations. Theoretical
results indicated a preference for nonplanar conformers due to steric
hindrance and internal rotations, in agreement with experimental NMR
and crystallographic data. Conformational searches and NMR prediction
further supported the predominance of EC1N2ZN3C4ZC7C8 and ZC1N2EN3C4ZC7C8 isomers in solutions. Biological
evaluation revealed selective cytotoxicity of compound 4e against HeLa and A549 cell lines (IC50 = 14.75 and 17.75
μM, respectively). Mechanistic studies in HeLa cells demonstrated
dose-dependent apoptosis induction, mitochondrial membrane hyperpolarization,
cytochrome c release, S-phase cell cycle arrest, and elevated intracellular
ROS. Co-treatment with the antioxidant N-acetylcysteine
(NAC) significantly mitigated these effects, suggesting a ROS-mediated
mitochondrial apoptotic pathway. This integrated experimental–theoretical
study highlights the importance of conformational dynamics in modulating
biological activity and provides valuable insights into the structure–activity
relationship of acridine–thiazolidinone hybrids. The results
support their potential as modular scaffolds for further development
of anticancer agents.