Host–guest inclusion complexation and release of 6,4′-dimethoxyflavone with β-cyclodextrin derivatives: computational and experimental insights

The limited aqueous solubility of hydrophobic flavonoids remains a major challenge for their effective utilization in pharmaceutical formulations. Herein, the inclusion complexation and release behavior of 6,4′-dimethoxyflavone (6,4′-DMF) with β-cyclodextrin (βCD) and its derivatives (MβCD, DMβCD, HPβCD, HAβCD, and SBEβCD) were systematically investigated using molecular docking, all-atom molecular dynamics (MD) simulations, LB-PaCS-MD enhanced sampling, and QM/MM (ONIOM) calculations, complemented by experimental validation, to elucidate the role of host substitution on molecular encapsulation and release in aqueous media. The results reveal that structural modification of βCD significantly alters host–guest interactions and solvent accessibility. SBEβCD exhibits the strongest inclusion capability, characterized by higher interfacial contact density, reduced solvent exposure, and enhanced dispersion-driven stabilization compared to other hosts. In contrast, native βCD and HAβCD display weaker encapsulation with greater solvent accessibility and less stable inclusion behavior. Analysis of release processes indicates that substituted cyclodextrins, particularly SBEβCD and HPβCD, provide more controlled and gradual guest dissociation, whereas βCD-based systems exhibit irregular release with transient re-association events. Phase-solubility studies confirm A_L-type behavior with 1:1 stoichiometry and demonstrate a clear increase in apparent stability constants in the order βCD < HPβCD < SBEβCD. These findings are supported by DSC, SEM, and NMR analyses, confirming successful inclusion and enhanced solubility. Furthermore, the SBEβCD inclusion complex shows improved cytotoxic activity against HeLa cells, highlighting the functional impact of solubilization. Overall, this study provides detailed insight into the relationship between cyclodextrin structure, intermolecular interactions, and drug solubilization and release in aqueous systems, offering guidance for the design of efficient host–guest delivery platforms.