Recovery of Phenolic Compounds from Eucalyptus globulus Wood Wastes using PEG/phosphate Aqueous Two-Phase Systems

Abstract

Polyethylene glycol (PEG) 2000/phosphate salt based aqueous two-phase systems (ATPS) were used to recover phenolic compounds with antioxidant activity from wastes of eucalyptus wood veneers. Combinations of two phosphate salts (K2HPO4 or mixtures of K2HPO4 and KH2PO4) with PEG 2000 were studied in order to understand the influence of pH and type of salt on phenols partition. Each ATPS was studied under different conditions (polymer/salt ratio, temperature, volume ratio and solid–liquid ratio). In all the ATPS studied, it was found that phenols had preference for the PEG-rich phase and it was demonstrated that the highest phenols recovery was favored by a high polymer/salt ratio, high temperature and a high volume ratio. The maximum total phenols yield in the top phase, 1.89 mg gallic acid equivalent/100 mg oven dried wood, was attained at 65 °C and a solid/liquid ratio of 0.5:10 using a PEG 2000/K2HPO4 ATPS. However, higher partition coefficients were attained for PEG 2000/K2HPO4–KH2PO4 ATPS. It was found that at low pH values higher partition of phenolic compounds was achieved. Extract analysis by RP-HPLC–ESI-TOF confirmed the presence of various phenolics compounds with antioxidant activity such as ellagic acid and quercetin 3-O-rhamnoside.