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Aurangabad Pharmacy College, Mitmita, Mumbai Nashik Highway, Chhatrapati Sambhajinagar (Aurangabad)
Cyclodextrins (CDs) are cyclic oligosaccharides widely used to enhance the solubility, stability, and bioavailability of poorly water-soluble compounds. Cyclodextrin (CD)-based inclusion complexation represents a widely adopted strategy to enhance the solubility and biopharmaceutical performance of poorly water-soluble molecules; however, the molecular determinants governing host?guest recognition and stabilization remain incompletely characterized. The present study provides a comprehensive mechanistic evaluation of cyclodextrin inclusion complexes through an integrated molecular modeling and experimental framework. Molecular docking and all-atom molecular dynamics (MD) simulations were employed to elucidate binding orientation, interaction energetics, conformational stability, and hydrogen bonding dynamics between ?-cyclodextrin (?-CD), hydroxypropyl-?-cyclodextrin (HP-?-CD), and a model hydrophobic drug candidate. Computational predictions demonstrated energetically favorable inclusion driven predominantly by hydrophobic interactions, van der Waals forces, and rim-associated hydrogen bonding, with entropy gain attributed to displacement of high-energy cavity water molecules. Experimental validation was performed using phase solubility analysis, Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and ^1H nuclear magnetic resonance (NMR) spectroscopy. An AL-type phase solubility profile confirmed 1:1 complex stoichiometry with enhanced apparent stability constants for HP-?-CD. Spectroscopic shifts, reduced crystallinity, and thermal behavior changes corroborated successful encapsulation and amorphization of the guest molecule. Importantly, strong concordance between computational and experimental findings substantiated the proposed mechanistic pathway of inclusion complex formation. This integrative approach advances molecular-level understanding of cyclodextrin?drug interactions and provides a rational platform for predictive design and translational optimization of cyclodextrin-based delivery systems. This study presents a comprehensive mechanistic exploration of cyclodextrin inclusion complexes using an integrated molecular modeling and experimental strategy. Molecular docking and molecular dynamics simulations were used to predict host?guest interactions, binding affinities, and conformational behavior of selected guest molecules within ?-cyclodextrin (?-CD) and hydroxypropyl-?-cyclodextrin (HP-?-CD) cavities. Complementary experimental characterization involved phase solubility studies, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) spectroscopy to validate complex formation mechanisms. The integration of computational predictions with experimental outcomes elucidated key structural determinants of complex stability and provided mechanistic insights into inclusion phenomena. The study offers a robust framework for rational cyclodextrin complex design in pharmaceutical and material science applications.
The development of efficacious pharmaceutical formulations is frequently constrained by poor aqueous solubility and limited biopharmaceutical performance of active pharmaceutical ingredients (APIs). It is estimated that more than 40% of newly discovered drug candidates exhibit low water solubility, resulting in suboptimal dissolution, erratic absorption, and reduced oral bioavailability. Among various solubilization strategies, cyclodextrin-based inclusion complexation has emerged as a versatile and clinically validated approach to enhance drug solubility, stability, and therapeutic performance. Cyclodextrins (CDs) are cyclic oligosaccharides composed of α-(1→4)-linked D-glucopyranose units arranged in a truncated cone geometry. The most commonly studied natural cyclodextrins—α-, β-, and γ-cyclodextrin—contain six, seven, and eight glucopyranose units, respectively. Their unique amphiphilic architecture, characterized by a hydrophobic internal cavity and hydrophilic external surface, enables the formation of non-covalent host–guest inclusion complexes with a broad range of hydrophobic molecules. Among them, β-cyclodextrin (β-CD) and its derivatives such as hydroxypropyl-β-cyclodextrin (HP-β-CD) are widely employed in pharmaceutical formulations due to optimal cavity dimensions, favorable safety profiles, and regulatory acceptance. The inclusion process is governed by a combination of hydrophobic interactions, van der Waals forces, hydrogen bonding, and entropic contributions arising from the displacement of structured water molecules within the cyclodextrin cavity. Although thermodynamic parameters such as stability constants and stoichiometry have been extensively studied through phase solubility analysis and spectroscopic techniques, detailed molecular-level understanding of host–guest recognition, binding orientation, and dynamic stability remains incomplete. Such mechanistic insight is essential for rational formulation design, especially when selecting appropriate cyclodextrin derivatives for specific drug candidates. Advances in computational chemistry now allow precise investigation of supramolecular interactions. Molecular docking provides rapid prediction of binding modes and interaction energies, while molecular dynamics (MD) simulations enable time-resolved analysis of conformational flexibility, hydrogen bond persistence, and solvent effects. When integrated with experimental characterization methods—including Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), nuclear magnetic resonance (NMR), and phase solubility studies—a comprehensive mechanistic framework can be established. Despite growing use of computational tools in pharmaceutical sciences, systematic correlation between molecular modeling predictions and experimental validation for cyclodextrin inclusion complexes remains underreported. Most studies focus either on thermodynamic evaluation or computational screening independently, without establishing mechanistic concordance between both approaches.
Pathan Gulnaz Nisar Ahmed*, Mohammed Shakir Ghouse, Mir Ashfaq Ali, Muzaffar Ahmed Farooqui, Syeda Saher Naaz, Siddiqui Hajra Yasmeen, Shaikh Mohd Mujtaba, Mechanistic Evaluation of Cyclodextrin Inclusion Complexes: A Molecular Modeling and Experimental Approach, Int. J. Sci. R. Tech., 2026, 3 (3), 308-320. https://doi.org/10.5281/zenodo.19029420
10.5281/zenodo.19029420