Optimization of Green Ultrasound-Assisted Extraction of Phenolic Compounds from a Species of the Scrophulariaceae Family

Ultrasound-Assisted Extraction (UAE) has emerged as a promising green technique for the efficient recovery of bioactive compounds from medicinal plants, due to its low energy consumption, reduced solvent use, and high extraction efficiency. In this study, UAE was applied to extract phenolic compounds from a medicinal plant species belonging to the Scrophulariaceae family. The influence of five key extraction parameters was investigated: ethanol concentration, extraction temperature, extraction time, solvent-to-solid ratio, and ultrasound power. A single-factor experimental approach was employed, where each parameter was varied individually while the others were kept constant, in order to assess its individual impact on total phenolic content (TPC). The Folin–Ciocalteu method was used to quantify TPC in the resulting extracts. The maximum TPC obtained for each parameter was as follows: 149.920 ± 3.12 µg GAE/mg dry extract at 60 °C, 52.601 ± 4.32 µg GAE/mg dry extract at 50 % ethanol, 119.687 ± 1.09 µg GAE/mg dry extract at 100 min, 110.53 ± 1.14 µg GAE/mg dry extract at 60 mL/g, and 91.209 ± 2.67 µg GAE/mg dry extract at 60 % ultrasound power. These values correspond to the highest TPC observed when each factor was optimized individually under fixed conditions for the others. Among all parameters tested, temperature exhibited the most significant impact on the extraction efficiency of phenolic compounds, while ultrasound power had a slight effect. Overall, this study confirms the potential of UAE as an environmentally friendly technique for the extraction of high-value phenolic compounds and highlights the importance of optimizing process parameters to improve extraction yield.