Deep eutectic solvent-based ultrasonic assisted extraction of polysaccharides and antioxidants from Astragalus hamosus L. seedpod

In this study, the efficiency of various solvents and techniques was compared for the extraction of polysaccharides and antioxidants from Astragalus hamosus. Among twenty solvents and four extraction techniques, ultrasonic-assisted extraction using choline chloride-urea (a deep eutectic solvent, DES) demonstrated the best performance. Extraction variables were optimized by the response surface methodology (RSM), and Box-Behnken design (BBD). Extraction yield and total carbohydrate content (TCC) were 44.5% and 2.90 mgGlu/gdw, respectively. Rhamnose, mannose and galactose (molar ratio: 0.34:1.18:1.0) were major monosaccharides in the extracted polysaccharides. Six antioxidant assays—total phenolic content (TPC), total flavonoid content (TFC), DPPH assay, ferric-reducing antioxidant power (FRAP), trolox equivalent antioxidant capacity (TEAC), and reducing power assay (RPA)—were used to evaluate antioxidant capacity. Additionally, different extraction methods, including ultrasonic-assisted, microwave-assisted, maceration, and Soxhlet extractions were compared.