Two New Polymorphs of Huperzine A Obtained from Different Dehydration Processes of One Monohydrate
Qi Zhang, Xuefeng Mei · Crystal Growth & Design · 2016
Two new polymorphs (forms IV and V) of huperzine A were obtained from the same hydrate form H1, which is currently commercially available, via dehydration processes under different conditions. Notably, the number of reported polymorphs of huperzine A is increased to five and the polymorphs with well-determined structures are increased to four. Forms IV and V were analyzed by single crystal X-ray diffraction (SCXRD) and X-ray powder diffraction (XRPD). In addition, form V was further characterized by Raman spectra, Fourier-transform infrared (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic vapor sorption (DVS). Finally, the mechanism for the two-phase transformation is discussed.