Mechanistic study on the solubility enhancement of puerarin by coamorphous technology

Puerarin (PUE), as an isoflavone component, has a wide range of pharmacological activities, while its poorly aqueous solubility limits the development of solid oral dosage forms. In this study, PUE along with nicotinamide (NIC) were prepared into the coamorphous system by solvent-evaporation method and characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). In addition, its dissolution behavior and solubilization mechanism were also investigated. PUE-NIC coamorphous was a single homogeneous binary system, with a single glass transition temperature at 35.1℃. In comparison to crystalline PUE, during the dissolution process, coamorphous PUE-NIC not only exhibited the "liquid-liquid phase separation" (LLPS) phenomenon, but the formation of A_p type complexation (1:1 and 1:2) between PUE and NIC molecules was also verified, which significantly improved the solubility of PUE and prolonged the supersaturation time, and would benefit its absorption.