Comparison of three strategies for the isolation of black tea thearubigins with a focus on countercurrent chromatography

Abstract

Three different methods from the literature for the fractionation and isolation of thearubigins in black tea (Roberts’ fractionation via liquid–liquid extraction, caffeine precipitation and high-speed countercurrent chromatography) were compared. The fractions were analyzed by both normal phase high-performance liquid chromatography (HPLC) on a diol-column and reverse phase HPLC. The methods were compared with regard to time consumption, yield and purity, showing that Roberts’ fractionation yielded the largest fractions while the caffeine precipitation demanded the least time. The purest TR fraction was obtained via high-speed countercurrent chromatography. Based on these results the isolation of thearubigins via countercurrent chromatography was selected for further investigations. Different techniques (high-speed-, spiral-coil- and high-performance-countercurrent chromatography) were applied, the established method was modified and an additional solvent system was developed to receive well-purified thearubigin fractions.