Crystallization-Based Isolation of Pure Rutin from Herbal Extract of Sophora japonica L.

Crystallization-based isolation of rutin from a plant extract of Sophora japonica L. was studied. Solid−liquid phase equilibria of rutin were determined in methanol, ethanol, and 2-propanol. Solvate formation and phase stability were investigated using X-ray powder diffraction and thermogravimetric analysis coupled with differential scanning calorimetry. The experiments revealed short-term stability of rutin ethanolate at ambient conditions in contrast to the rutin trihydrate phase, which was found to be stable. On the basis of the particular solubility behavior of both solvate phases in ethanol, a seeded crystallization process in batch and semicontinuous operation mode was designed and successfully performed. Crystalline rutin trihydrate of 99% purity was isolated with overall process yields of 95 and 87% in the batch and semicontinuous processes, respectively. Because of their cost-efficiency and robustness, the purification processes are attractive to be applied directly in countries where the plants are growing.