Optimization of ultrasonic-assisted extraction (UAE) of phenolic and antioxidant compounds from Ephedra foeminea Forssk. using response surface methodology (RSM)

Abstract

Ephedra foeminea Forssk., a Mediterranean shrub with diverse traditional medicinal applications, is rich in bioactive metabolites [1,2]. This study optimized the ultrasonic-assisted extraction (UAE) of phenolic and antioxidant compounds from E. foeminea using response surface methodology (RSM). A circumscribed central composite design was applied to assess the influence of four variables—solvent volume (20–40 mL/g), ethanol concentration (50–70%), sonication time (10–20 min), and temperature (35–45 °C)—on extraction yield (Y%), total phenolic content (TPC), and radical scavenging activity (RSA%). The enhanced statistical models provided the following optimal conditions for each output: Y% (11.93 ± 0.09%) at V = 28.2 mL/g, E = 67.9%, S = 19.1 min, T = 39.3 °C; TPC (3.06 ± 0.06 mg GAE/g) at V = 32.6 mL/g, E = 65.1%, S = 17.3 min, T = 40.5 °C; and RSA% (90.63 ± 1.08%) at V = 31.8 mL/g, E = 66.7%, S = 19.7 min, T = 40.5 °C. High-performance liquid chromatography (HPLC) confirmed that the RSM-optimized UAE conditions enriched phenolics, including gallic acid, luteolin, and apigenin [3]. Principal component analysis (PCA) showed strong correlations between TPC and RSA%, with PC1 and PC2 explaining 98.0% of the variance. These findings establish RSM-optimized UAE as a potent method for extracting antioxidant-rich phenolics from E. foeminea, supporting its potential use in functional and therapeutic applications [4,5].