Response surface methodology for the green obtention of polyphenols from yerba mate

Optimal conditions for polyphenols extraction from plants are moderate conditions and being water-based is mandatory. In this work, a response surface methodology (RSM) was used to attain optimal conditions for polyphenols extraction from yerba mate (YM, South-America infusion) using water as solvent under ultrasound (US). The following parameters were varied: mass of YM/volume of water (YM/W), pH, temperature, and time. The optimal conditions were 90°C with a YM/W of 150 g L⁻¹ for 5 min, at which the highest total polyphenol content (TPC) concentration (11,300 mg GAE L⁻¹) was found, together with an antioxidant activity of 132 mmol Trolox equivalent (TE) L⁻¹ of extract. The conditions obtained from the RSM method were applied to other methods as follows: extraction without stirring, magnetic stirring assisted extraction and US with magnetic stirring assisted extraction. Results indicated that the US-assisted extraction was the most efficient for extracting polyphenols under these conditions. This study helps to developing an eco-friendly and cost-effective experimental design, reducing the production of wastes, and using a very fast water-based method.