Comprehensive physicochemical and functional characterization of mechanochemically prepared α-mangostin/cyclodextrin inclusion complexes

α-Mangostin (αMg) is a bioactive xanthone derivative with strong antioxidant activity; however, its extremely poor aqueous solubility and formulation instability limit its pharmaceutical application. In this study, inclusion complexes of αMg with α-, β-, and γ-cyclodextrins (CDs) were prepared using a solvent-free mechanochemical co-grinding method, and their physicochemical properties, antioxidant activity, and cellular safety were systematically evaluated. Powder X-ray diffraction revealed the disappearance of characteristic diffraction peaks in all co-ground samples, indicating amorphization and molecular-level dispersion. Near-infrared spectroscopy and nuclear magnetic resonance spectroscopy analyses (nuclear Overhauser effect spectroscopy and diffusion-ordered spectroscopy) demonstrated cavity-size-dependent inclusion behaviors, including hydrogen bond rearrangement and partial aromatic insertion, which were particularly pronounced in the γCD system. Phase-solubility studies showed significant solubility enhancement, with stability constants in the order βCD > γCD > αCD, reflecting the geometric compatibility between the αMg and CD cavities. Dissolution testing in fasted-state simulated intestinal fluid confirmed markedly improved dissolution profiles for all CD complexes compared with αMg alone. Functionally, the CD complexes exhibited enhanced H₂O₂ scavenging activity over a concentration range of 10–250 µM. Furthermore, cytotoxicity and H₂O₂-induced cell-injury assays using Caco-2 cells demonstrated that CD complexation mitigated αMg-associated cytotoxicity and improved cellular tolerance, particularly at concentrations of 15–25 µM and above. Overall, these findings indicate that mechanochemical co-grinding is a green and effective strategy for achieving cavity-selective inclusion, improved dissolution, enhanced antioxidant activity, and favorable safety profiles of αMg, providing a promising formulation platform for poorly water-soluble natural products. Phase-solubility analysis demonstrated significant solubility enhancement of αMg in the presence of cyclodextrins, with apparent stability constants in the order βCD > γCD > αCD. In addition, the αMg/CD complexes exhibited improved dissolution behavior in biorelevant FaSSIF medium. • Solvent-free mechanochemical co-grinding enables cavity-size-dependent inclusion of α-mangostin with CDs. • PXRD, NIR, and NMR analyses reveal molecular dispersion and host–guest interactions in co-ground systems. • Phase-solubility studies show enhanced solubility with stability constants in the order βCD > γCD > αCD. • Cyclodextrin complexation improves dissolution of α-mangostin in biorelevant FaSSIF medium. • Inclusion complexes enhance H₂O₂ scavenging activity and reduce α-mangostin cytotoxicity in Caco-2 cells.