Insight into the Phase Transformation among Various Solid Forms of Baicalein

A new polymorph and three hydrates of baicalein, a widely prescribed anti-inflammatory TCM drug, were discovered through comprehensive polymorph screening experiments. The forms were fully characterized by a range of analytical techniques, including PXRD, Raman spectra, FTIR, HSM, SEM, TGA, DSC, and DVS. Single crystal structures and the transformation pathways among different polymorphs and hydrates are discussed in detail. Single-crystal-to-single-crystal transformation behavior between monohydrate and hemihydrate was revealed. Thermodynamic stability, hygroscopicity, and powder dissolution behavior were investigated. The results show that the newly discovered form γ presents better dissolution behavior and remarkably greater apparent solubility compared with the current widely used marketed drug substance.黄芩素（baicalein）是一款临床广泛应用的抗炎中药（TCM）药物。本研究通过全面的多晶型筛选实验，发现了其一种新晶型及三种水合物。本研究采用包括X射线粉末衍射（PXRD）、拉曼光谱、傅里叶变换红外光谱（FTIR）、热台显微镜（HSM）、扫描电子显微镜（SEM）、热重分析（TGA）、差示扫描量热法（DSC）以及动态水蒸气吸附（DVS）在内的多种分析技术，对上述晶型与水合物进行了全面表征。研究详细讨论了单晶结构以及不同晶型与水合物间的转化路径，并揭示了单水合物与半水合物之间的单晶-单晶转化行为。此外，本研究还对其热力学稳定性、吸湿性以及粉末溶出行为进行了考察。结果表明，新发现的γ晶型相较于当前广泛使用的上市原料药，展现出更优异的溶出性能，且表观溶解度显著更高。