Temperature-sensitive homogeneous magnetic fluid based aqueous two-phase system for the purification of polyphenols from crude extract of green tea leaves

In this work, the first temperature-sensitive homogenous magnetic fluids have been prepared, mainly composed of non-toxic, non-volatile, biodegradable and thermo-sensitive poly(propylene glycol) 600. These magnetic fluids exhibited not only response to an external magnetic field, but have also displayed a significant temperature-sensitive property. Moreover, these magnetic fluids were simply prepared by mixing raw materials. The first temperature-sensitive magnetic fluid based aqueous two-phase systems have been developed for the purification of polyphenols from crude extract of green tea leaves. This novel system has the advantages of easy preparation, swift extraction, efficient magnet-assisted phase separation and temperature-induced recovery, especially organic solvent free for the whole extraction and recovery processes. In this study, phase behaviors and correlation results were studied in detail, providing valuable reference for the extraction applications. Selective extraction and recovery of tea polyphenols were studied and optimized. Under the optimum conditions, more than 90 % of epicatechin and less than 10 % of theophylline were extracted. Furthermore, for the extraction and recovery of tea polyphenols from the crude extract of green tea leaves, the main impurity alkaloid such as caffeine and theophylline was not found in the purified tea polyphenols product. The recovered magnetic fluid could be recycled for at least 5 times with steadily good performances. This novel, simple and green temperature-sensitive homogenous magnetic fluid based aqueous two-phase system is showing great potential in the industrial purification of tea polyphenols as well as many other natural products.