Study of curcumin partitioning in polymer-salt aqueous two phase systems

Abstract

Curcumin is a polyphenolic compound derived from Curcuma longa, which has a wide range of pharmacological applications and it constitutes 2–5% of turmeric. An efficient separation method is needed for the purification of curcumin. A polymer-salt aqueous two-phase system (ATPS) has been developed for curcumin separation. The applied polymers include polyethylene glycol (PEG) 6000 and 2000, polypropylene glycol (PPG) 400 and a three-block copolymer of PEG-PPG (Pluronic L35), as well as magnesium sulfate and sodium sulfate. The phase behavior of the ATPSs and curcumin partitioning as well as the effect of cation, PEG molecular weight, polymer type and temperature (5, 15 and 25 °C) have been investigated. According to obtained results, Na2SO4 due to its high salting out effect is more suitable for the partitioning of curcumin. By increasing the molecular weight of the polymer, the hydrophobicity of the top phase and consequently, the partitioning increases. The partitioning of curcumin in the determined optimum PEG-salt (PEG6000-Na2SO4) and PPG-sodium sulfate ATPSs have been obtained 67 and 25, respectively. The lower volume ratio of the phases decreases the partitioning ability of PPG400-Na2SO4 ATPS. Pluronic L35-Na2SO4 was able to reach the complete partitioning of curcumin. As predicted by the calculated differences in solubility parameter applying group contribution method, this system has the most partition ability due to self-aggregation in aqueous solutions and by decreasing the temperature, the partition coefficient decreased, but it was still more than the other polymers.