Comparative Analysis of Traditional and Modern Extraction Techniques for Phenolic Compounds From Leontopodium and Optimization of Extraction Process Using Response Surface Methodology

Phenolic compounds from Leontopodium leontopodioides (LLB) are natural bioactive constituents with potential antioxidant activity. This study compared reflux extraction (RE), microwave-assisted extraction (MAE), and ultrasound-assisted extraction (UAE) for recovering total flavonoids (TFC) and total phenolic content (TPC) from LLB. Based on the comparative results, UAE was further optimized using response surface methodology. The effects of habitat on TFC and TPC contents and the antioxidant activity of LLB extracts were also evaluated. Under the tested operating conditions, UAE with 70% ethanol showed the best overall extraction performance and was therefore selected for optimization. The optimized UAE conditions for TFC were an extraction time of 61 min, a solid-to-liquid ratio of 1:27 (g/mL), an ultrasound power of 610 W, and an extraction temperature of 58°C, yielding 40.58 ± 0.94 mg/g DW. For TPC, the optimum conditions were 40 min, 1:24 (g/mL), 430 W, and 57°C, respectively, yielding 26.38 ± 0.57 mg/g DW. LLB collected from desert grassland exhibited the highest TFC content and the strongest DPPH-, ABTS-, and hydroxyl-radical-scavenging activities, as well as the greatest reducing power. In contrast, TPC did not differ significantly among habitats (p > 0.05). These findings provide a basis for optimizing the extraction of phenolic constituents from LLB and support its future processing and utilization as a source of bioactive ingredients.