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.