Optimization of eco-friendly ultrasonic probe-assisted extraction from Stevia rebaudiana Bertoni using response surface methodology and antioxidant evaluation.

In this study, an environmentally friendly ultrasonic probe-assisted extraction (UPAE) method was modeled and optimized to enhance the recovery of rebaudioside A, resveratrol, and total phenolic content (TPC) from Stevia rebaudiana Bertoni using response surface methodology. A central composite design was applied to investigate the effects of extraction time (1-9 min), ethanol concentration (0-100 %), plant amount (0.1-0.5 g), and ultrasonic frequency (20-28 kHz). Extraction efficiency was evaluated through TPC analysis and quantitative determination of rebaudioside A and resveratrol by high-performance liquid chromatography (HPLC). Green chemistry principles were integrated into extraction and analytical procedures by employing ethanol as a sustainable solvent and eliminating toxic organic modifiers. Optimal conditions were determined as 7 min extraction time, 75 % ethanol, 0.2 g plant material, and 22 kHz frequency. Under these conditions, rebaudioside A, resveratrol, and TPC were obtained as 281.59 μg/mg, 5.74 μg/mg, and 54.17 mg GAE/g, respectively, showing strong agreement with model predictions. The optimized extract exhibited high total flavonoid content and antioxidant capacity as confirmed by DPPH, FRAP, and CUPRAC assays. The proposed UPAE-HPLC approach provides a sustainable and efficient platform for the recovery of natural sweeteners and antioxidant compounds from Stevia rebaudiana, with potential applications in food, nutraceutical, and pharmaceutical industries.