| Abstract: | Two new solvates of ginsenoside compound K (nonstoichiometric hydrate/CKH and methanol solvate/CKM) have been discovered and characterized in this paper. They were obtained through cooling crystallization in different solvents, and CKM could be prepared by transformation from CKH as well. The solvates were analysed by Power X‐ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and fourier transform infrared (FTIR) spectroscopy. From the thermal studies, it is shown that the two new products are both solvates with different onset melting points. The PXRD and FTIR data support different crystal structures of them. It also describes the solution‐mediated phase transformation from CKH to CKM with a combination usage of process analytical technology tools. It is shown that the transformation process can be divided into three stages. The results reveal that seeding and low temperature help to accelerate the transformation, but initial solution concentration do little to the transformation kinetics. The kinetics and the rate‐controlling step for the transformation depend on the nucleation of the CKM. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) |
