Optimization of the gallic acid extraction using ionic-liquid-based aqueous two-phase systems

Gallic acid is an interesting natural compound because of its antioxidant, anti-inflammatory, antifungal and antitumor properties. It is present in relatively high concentrations in a number of biomass sources and in industrial wastes from where it could be extracted. Aiming at developing benign and efficient extraction/purification processes for gallic acid, aqueous two-phase systems (ATPS) composed of ionic liquids (ILs) and inorganic salts were investigated. Several combinations of ionic liquids and inorganic salts were studied to understand the influence of the ionic liquid structure and of the pH of the aqueous medium on the gallic acid partitioning. It is here shown that at low pH values the non-charged form of gallic acid (or other phenolic compounds) preferentially migrates for the ionic-liquid-rich phase whereas its conjugate base preferentially partitions for the salt-rich phase. The results indicate that IL-based ATPS can be the basis of new extraction/purification processes of gallic acid from natural matrices, and improved extractions are obtained using acidic aqueous solutions. (C) 2012 Elsevier B.V. All rights reserved.