Application of Response Surface Methodology to Obtain an Extract of the Herb Trifolium pratense L. with High Antioxidant Activity and Total Polyphenol Content

This is the authors' abstract. We don't add key points for this paper.

Mathematical modelling, including the use of response surface methodology (RSM), facilitates the analysis of complex relationships between various extraction process parameters and the bioactive properties of plant extracts. The aim of this study was to optimise selected parameters of the ultrasound-assisted extraction (UAE) process of the herb Trifolium pratense L. to yield extracts with high antioxidant activity (AA-DPPH) and total polyphenol content (TPC). The following parameters were investigated: solvent selection (methanol, ethanol, isopropanol, and n-propanol), the alcohol concentration used as the solvent (from 20% v/v to concentrated), and extraction time (2–15 min). The optimal extraction conditions, depending on the solvent used, comprised alcohol concentrations of 49–61% v/v and extraction times of 3–13 min. Under these optimal conditions, the extracts exhibited high antioxidant activity (methanol 4.21 ± 0.02, ethanol 3.92 ± 0.02, n-propanol 3.84 ± 0.02, and isopropanol 3.72 ± 0.02 mmol Trolox/L) and high total polyphenol content (n-propanol 0.84 ± 0.01, ethanol 0.81 ± 0.01, isopropanol 0.76 ± 0.01, and methanol 0.72 ± 0.01 g GA/L). The log p value of the optimised extracts was below zero (except for the isopropanol extract), indicating their hydrophilic nature, which is attributed to the presence of polar phenolic compounds. The extracts obtained via optimised UAE were characterised by a high content of bioactive compounds with antioxidant potential, suggesting their potential application in the pharmaceutical and cosmetic industries.