Ultrasonic extraction of Inula viscosa: Enhancing antioxidant bioactivity and its application in sunflower oil as an antioxidant

The objective of this study was to optimize the ultrasound-assisted extraction (UAE) of Inula viscosa, focusing on the extraction yield, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity and to evaluate its antioxidant effect in sunflower oil (SFO) storage. A water–ethanol binary solvent system was applied to extract bioactive components sustainably. Extraction parameters (temperature, time, ethanol concentration, and solvent-to-solid ratio) were optimized using a central composite rotatable design, achieving high accuracy (R² > 0.974). Optimum conditions were 54 % (v/v) ethanol concentration, 60 °C, 31 min, and a 15 (mL/g) solvent-to-solid ratio resulting in a yield of 24.72 g/g (%), TPC of 489.54 mg gallic acid/g, TFC of 149.81 mg quercetin/g, and IC₅₀ of 18.21 µg/mL. UAE outperformed Soxhlet extraction in yield, bioactive compound composition, and antioxidant capacity. Strong correlations were found between TPC, TFC, and antioxidant capacity, with TFC having a more significant impact. I. viscosa extract was found to be a potent antioxidant and delay the oxidation of SFO during accelerated storage due to peroxide value and oxidative induction time analysis. Microstructural analysis illuminated the structural changes induced by the extraction methods. In conclusion, this study not only optimized UAE of I.viscosa, showing superior efficiency and antioxidant capacity, but also demonstrated the practical application of I.viscosa in enhancing sunflower oil shelf life, thereby providing valuable insights for the field of food engineering and antioxidant research.