Parameters determining the agglomeration behavior of anhydrous L-ornithine-L-aspartate (LOLA) crystals prepared by drowning out crystallization

Crystallization of L-ornithine-L-aspartate (LOLA) by drowning out was performed for the production of the anhydrous form of LOLA. The needle-like LOLA crystals were formed and spherically agglomerated during precipitation in a semibatch crystallizer. The primary crystal size in the agglomerate remains unchanged after completion of the crystallization. Therefore, the agglomeration process of primary crystals played an important role for controlling LOLA crystal size. The agglomeration of LOLA crystals was governed by not only the physico-chemical parameters such as the temperature and feed concentration, but also the hydrodynamic parameters such as agitation speed and feeding rate. The crystal size and the shape have been shown to be important factors in product impurity and flowability. Thus, the optimum condition of LOLA crystallization process by drowning-out could be obtained.     

Drowning-out crystallization of l-proline: Effect of anti-solvent composition and processing parameters on crystal size and shape

Crystallization of l-proline was investigated using a drowning-out method. Due to the high water and alcohol solubility of l-proline, the recovery of an l-proline product by precipitation using the drowning-out method required suitable anti-solvents selected from immiscibility and solubility studies. Through past experience, acetone and NMP were carefully chosen for analogy and solubility tests in pure anti-solvent. Although phase separation occurred in acetone, ultrasound was used to mix the two immiscible phases and generate fine emulsion droplets. l-proline crystals were obtained using NMP with a general drowning-out method. A spherical agglomerate of l-proline was also obtained using acetone by emulsion solvent diffusion methods. The ultrasound power controlled the agglomerate sizes, and the agglomerate surface transformed from amorphous to crystalline as the residence time increased. Alternatively, when NMP was used as an anti-solvent, l-proline monocrystals with needle type morphology were produced.     

Isolation and purification of four flavone C-glycosides from antioxidant of bamboo leaves by macroporous resin column chromatography and preparative high-performance liquid chromatography

The present study investigated a robust method for the preparation of four flavone C-glycosides, i.e. orientin, homoorientin, vitexin and isovitexin, which were prepared from an ethanol aqueous extract, i.e. antioxidant of bamboo leaves (AOB), by AB-8 resin-based column chromatography and preparative high-performance liquid chromatography (HPLC) using a mobile phase consisting of 10% and 15% (v/v) of acetonitrile and 1% acetic acid. These flavone C-glycosides were further purified by the drowning-out crystallization method using methanol and water as drowning-out anti-solvents and salting-out agents, respectively. The purity was assessed by analytical HPLC and the confirmation of chemical structures was performed by IR, MS, NMR and UV spectroscopy. Orientin (49 mg), homoorientin (142 mg), vitexin (15 mg) and isovitexin (62 mg) were prepared from 6.5 g of crude column chromatography fraction obtained from 5 L of AOB concentrated solution. The present method is robust and suitable for preparing available quantities of pure flavone C-glycosides and the quantification of orientin, homoorientin, vitexin and isovitexin in bamboo leaves.