Optimization of ultrasonic-assisted extraction conditions for polyphenols from Algerian Phlomis Crinita (Cav.) by response surface methodology

The aim of this study is to determine the optimal conditions for ultrasonic-assisted extraction (UAE) to maximize the yield, total polyphenols content and antioxidant activity of Algerian Phlomis crinita (Cav.) extracts. The effect of extraction parameters is evaluated by response surface methodology (RSM). The antioxidant activity of the extracts is determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. The maximum yield obtained from ultrasound-assisted extraction is 18.54% (g per 100 g) with a total polyphenols content of 175.75 mg of Gallic acid equivalent (GAE) per gram of extract and an antioxidant activity expressed by the value of the half-maximal inhibitory concentration (IC₅₀) of 7.51 mg L-1 of Phlomis crinita extracts. The optimum conditions for this result are 60 min for extraction time, ultrasonic power of 40 W, a ratio of 1:20 g mL-1 for vegetable matter/solvent and a methanol concentration of 70% (v v-1). The results confirmed the efficiency of ultrasonic extraction and response surface methodology in optimizing the extraction of bioactive compounds from Phlomis crinita.