Experimental and DFT Calculation Probing the Interaction of Simvastatin-β-Cyclodextrin-Ammonium Acetate Ternary Complex

Simvastatin(Sim) is widely used for the prevention of cardiovascular disease and cancer treatment, but its solubility and bioavailability are poor. Therefore, the selection of β-cyclodextrin and ammonium acetate was explored to prepare ternary Sim inclusion complexes by freeze-drying method, the formation of ternary complex was confirmed by Electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC), Scanning electron microscope (SEM), and X-ray diffraction (XRD) method. Compared to its solubility in pure water, the solubility of Sim in ternary complexes has increased by 46 times. The stable structure of complex was explored through 1H Nuclear magnetic resonance spectroscopy (NMR) and Density functional theory (DFT) calculation, Natural Bond Orbital (NBO) analysis revealed the interaction mechanism, where charge transfer and hydrogen bonding networks in the complex led to the locking of the Sim lactone ring within the narrower ring of β-CD, the NH₄Ac component leads to more hydrogen bond formation and enhances stability of drug. The proposed approach is a innovative systems for improving the solubility and stability of Simvastatin.