Thermo-sensitive aqueous biphasic extraction of polyphenols from Camellia sinensis var. assamica leaves

Abstract

Abstract Tea is receiving great interests due to potential health benefits associated with long term consumption. Theaflavins, thearubigins and catechins presence in black tea possess high antioxidant capacity and biological activities. Concentration and extraction of these potent antioxidants from Camellia sinensis var. assamica leaves with an aqueous biphasic system (ABS) composed of thermo-sensitive ethylene oxide–propylene oxide (EOPO) random copolymer and salt was demonstrated. The thermo-sensitive EOPO can be recovered upon heating above a lower critical solution temperature (LCST). The partition coefficients of polyphenols based on phenolic content in the EOPO/salt ABS were determined to understand the partition preference of the polyphenols in the extraction system. Effects of different types of salts, tie-line length (TLL), volume ratio ( V R ), sample loading, pH and equilibration time on the extraction efficiency of polyphenols using ABS were evaluated. The EOPO polymer recovery was performed after the primary aqueous biphasic extraction. The highest recovery of polyphenols in EOPO-rich phase was obtained in EOPO 2500/sulphate ABS at pH of 7.0, TLL of 41.4% (w/w), V R of 1.0, sample loading of 0.3% (w/w) and equilibration time of 12.5 min. A total of 96.54 ± 0.09% of polyphenols was recovered in the EOPO-rich phase of the primary EOPO 2500/sulphate ABS with a partition coefficient of polyphenols ( K pc ) of 26.93 ± 0.76. Later, 95.2% of the EOPO 2500 polymer was recovered after the thermo-induction of the polymer-rich phase. This study has successfully demonstrated the feasibility of thermo-sensitive ABS in the extraction and enrichment of antioxidants from plant sources.