Formulation of Apigenin-Cyclodextrin-Chitosan Ternary Complex: Physicochemical Characterization, In Vitro and In Vivo Studies

The current investigation was performed with an aim to improve the aqueous solubility, dissolution rate, and thus the biological activity of apigenin (APG) using the solubilizers hydroxypropyl beta-cyclodextrin (HPβCD) and chitosan (CTSN). A binary and ternary inclusion complexes of APG with HPβCD and CTSN were prepared by physical mixing, fusion, and solvent evaporation methods. The liquid state characterization of the APG, the solubilizers, and the physical and chemical interactions between them was done through phase solubility approach. The solid-state characterization was performed by proton nuclear magnetic resonance (1H-NMR), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD). The in vitro dissolution test and antioxidant activity and in vivo anti-inflammatory activity of the ternary inclusion complex in albino rats were performed to assess the performance of the APG. Phase solubility study results revealed a remarkable increase in apparent stability constant (Kc) and complexation efficiency (CE) of HPβCD in presence of CTSN in ternary complex with above 8 folds more increment in solubility of APG than its binary complex. The in vitro dissolution rate, antioxidant activity, and the anti-inflammatory effect of the APG ternary inclusion complex were found to be significantly higher than that of pure APG. Solid state characterization confirmed the formation of a ternary inclusion complex. 1H-NMR study gave more insight at molecular level into how different groups of APG were responsible for complex formation with the HPβCD and how CTSN was significantly influencing on the APG-HPβCD complex formed. Nevertheless, pharmacokinetic and histopathological studies of our APG-HPβCD-CTSN ternary complex would yield much rewarding results.