Thermodynamics for curcumin (Curcuma longa L.) partitioning in the alcohol–salt aqueous two‐phase system

Abstract

AbstractBACKGROUNDCurcumin is a polyphenol used as a natural colorant or spice with pharmacological properties including analgesic, anti‐inflammatory, anticarcinogenic and antioxidant. In this work the partition of curcumin was carried out in an aqueous two‐phase system (ATPS) under different conditions.RESULTSLiquid–liquid equilibrium data for the ATPS composed of 2‐propanol + sodium phosphate + water were determined experimentally by the turbidimetric method at temperatures T = 288.15, 293.15, 298.15 and 303.15 K and pH values 4.0 and 5.0. The phase‐forming and salting‐out capability of the mentioned salt were discussed by determination of the exclusion volume effect (EEV) and salting‐out coefficient. The partition of curcumin was carried out. In order to investigate the driving forces that govern the curcumin partition we conducted a thermodynamic study by isothermal titration calorimetry (ITC). The Gibbs free energy transfer (ΔtrG), transfer enthalpy variation (ΔtrH) and transfer entropy variation (TΔtrS) were measured during the dye partition for the systems at 298.15 K.CONCLUSIONThe increase in the pH value promoted an increase in the salting‐out effect as well as in the exclusion volume value. It was observed that the dye had a strong tendency to transfer to the alcohol‐rich top phase, showing Kp high values (13.725–112.764). Thermodynamic analysis indicated that curcumin partition in the ATPS at 298.15 K was entropically driven to the top phase. The high values of theoretical recovery, selectivity and partition coefficient obtained in this study show that the investigated systems may be a promising alternative for curcumin pre‐concentration and purification. © 2019 Society of Chemical Industry