Deep eutectic solvent mediated extraction of polysaccharides and antioxidants from Persian manna (Taranjabin): Comparison of different extraction methods and optimization by response surface methodology

In this work, sixteen deep eutectic solvents and four conventional solvents were tested for polysaccharide and antioxidant extraction from Persian manna (Taranjabin). Choline chloride-xylitol was selected as the best solvent. Extraction variables such as temperature (T), time (t), water content in DES (WC), and liquid-to-solid ratio (L/s) in ultrasonic-assisted extraction were optimized by the Box-Behnken design and response surface methodology (RSM). At optimal conditions (T = 70 ◦C, WC = 10% v/v, L/s ratio = 100 mL/g and t = 40 min), total carbohydrate content and extraction yield were 2.5 mg Glu per gram of dried and deffated material (gddm) and 55.5%, respectively. Based on monosaccharide composition analysis, extracted polysaccharides had rhamnose, arabinose, glucose and galactose (molar ratio: 1.68:0.69:1.00:2.16). Different antioxidant assays such as total phenolic and total flavonoid content, DPPH assay, trolox equivalent antioxidant capacity, ferric-reducing antioxidant power and reducing power assay were also performed. Optimal extraction conditions for total phenolic content were T = 70 ◦C, WC = 50% v/v, L/s ratio = 100 mL/g and t = 20 min. Experimental TPC was 2.15 mg GAE/gddm. Extraction efficiencies of the DES-based ultrasonic-assisted method for total carbohydrates and phenolics contents (2.50 mg Glu/gddm and 2.15 mg GAE/gddm) were better than microwave-assisted extraction (1.03, 1.15), maceration (0.64, 0.72) and Soxhlet methods (1.13, 0.88). In comparison of DES and water in ultrasonic-assisted extraction, extraction improvement for DES (choline chloride-xylitol) was about 26% in TCC (1.057 vs. 0.839 mg Glu/gddm), and 56% in TPC (0.528 vs. 0.339 mg GAE/gddm) with respect to water.