Characterization, solubility and stability of amentoflavone polymorphs

Amentoflavone (AMF) is a biflavonoid existing in several medicinal plants possessing anti-tumor, anti-inflammatory activities. However, few studies concern about the polymorphic behavior of this active pharmaceutical ingredient (API). In this study, two polymorph forms (form I, Ⅱ) and one amorphous form of AMF were prepared and characterized by scanning electron microscopy, differential scanning calorimetry, thermal gravimetric analysis, single crystal X-ray diffraction, powder X-ray diffraction, and Fourier-transform infrared spectroscopy. Form Ⅱ was identified as a water-ethanol solvate. The solubility properties and physical stabilities of three forms were also investigated. Amorphous AMF demonstrated the best solubility and was dissolved faster than form Ⅰ and form Ⅱ during dissolution. At 40 °C/ 75% RH, form I and amorphous AMF were more stable than form Ⅱ. This study would provide valuable supporting for the further pharmaceutical dosage form development of AMF.