Selective extraction of saponins from Ilex paraguariensis St.-Hil. unripe fruits

The unripe fruits of mate tree are an abundant source of saponins, known natural surfactants. The aim of this work was to evaluate non-conventional extraction techniques for the selective extraction of saponins from unripe fruits of yerba mate. Different ultrasound power (282-565 W cm−2) and electric field (25-50 V cm−1) intensities were assayed, as well as different solvent flow rates (1.67-2.78 × 10−4 kg s−1) for pressurized liquid extraction applied to the fruits. In this study, the pressurized liquid extraction was more selective for saponins than ultrasound and electric field. At optimal conditions, the extraction using ultrasound and electric field resulted in yields of 6.42% and 6.83% of saponin equivalent per gram of extract, respectively. Although pressurized liquid extraction showed low brute extracts yields, it was highly selective for saponins, yielding up to 10.09%. Mathematical models, suitable for each extraction technique, were used to model the experimental data.