Optimization of microwave-assisted extraction of polyphenols and antioxidant activity in Reichardia tingitana and Atriplex halimus via response surface methodology

The demand for natural, plant-derived polyphenols is growing in both academic and industrial sectors, owing to their strong therapeutic potential, including antioxidant, antiviral, anti-inflammatory, and anticancer properties. A comprehensive study investigating the polyphenolic profile and antioxidant potential of Reichardia tingitana and Atriplex halimus utilizing microwave extraction technique, supported by response surface methodology-based optimization, remains unexplored. Comparison of the polyphenol contents in the mentioned plants extracted with microwave-assisted methods demonstrated that R. tingitana possess high phenolic contents (93.48-123.35 mg GAE/g DW) than A. halimus (54.64–84.28 mg GAE/g DW). The single factor optimization experiments demonstrated that 50% ethanol-water mixture outperform in extracting polyphenols (102.45–123.35 for R. tingitana and 63.39–84.28 for A. halimus ) followed by 50% acetone-water and methanol/water respectively, whereas ethyl acetate-water resulted in the lowest TPC (93.48–109.73 mg GAE/g DW for R. tingitana and 54.64–70.57 mg GAE/g for A. halimus ) respectively. The MAE extraction parameters (MW power, temperature, time and ethanol%) were further optimized by response surface methodology with Box-Behnken design. The outcomes of the Box-Behnken design demonstrated that optimum TPC contents could be extracted with 500 W MW power at 75 ⁰ C temperature, 7 min of contact time and 70% ethanol concentration, providing the polyphenol yield ( R. tingitana  = 129.43 mg GAE/g DW and A. halimus  = 91.87 mg/g DW plant extract). Finally, the optimized plant extracts were evaluated for antioxidant activities using ABTS assay. Prominent correlation was found to exist between the antioxidant activities and polyphenol contents of the extracts.