Fractionated extraction of polyphenols from mate tea leaves using a combination of hydrophobic/ hydrophilic NADES

A new methodology for the selective extraction of antioxidants from mate tea leaves (and decaffeinated mate tea leaves), using different natural deep eutectic systems (NADES), is reported in this paper. A fractionated extraction was carried out and the optimization of the extraction conditions such as solid/liquid ratio, temperature, time, stirring and the use of ultrasound assisted extraction (UAE) technology was performed. The results demonstrate that a sequential extraction using, in a first step, an hydrophobic system Men:Lau (2:1) and, in a second step, an hydrophilic lactic acid-based NADES, leads to two distinct extracts: the first one rich in pigments and the second one rich in polyphenols. NADES systems were able to extract 30% more of the polyphenolic components of the mate tea leaves matrices, when compared with traditional solvents/techniques. Moreover, it has been shown that the incorporation of the extract in the NADES, compared to the same extract in aqueous medium was beneficial for the stabilization of the antioxidants. It maintains their functionality at least for three months, reaching 41% more versus the extracts obtained by traditional solvents/techniques. The absence of caffeine in the extracts did not shown to have any effects on the stability results.