Optimization of Green Extraction of Polysaccharides and Antioxidants from Purgative Manna Using Deep Eutectic Solvents and Ultrasonic-Assisted Technique

In this work, the ultrasonic technique is combined with Deep Eutectic Solvent (DES) was used as a green method for the extraction of polysaccharides and antioxidants from a rarely studied manna, Purgative manna (Shirkhesht). Between twenty solvents, maximum values of Total Carbohydrate Content (TCC) and Total Phenolic Content (TPC) were obtained for choline chloride-lactic acid. Response surface methodology (RSM) and the Box-Behnken design were used for the optimization of ultrasonic-assisted extraction. Optimal values of experimental parameters to achieve the highest total carbohydrate content (7.62 mg Glucose/gram of dry weight), total phenolic content (3.45 mg Gallic acid equivalent/gram of dry weight), and yield (77.7%) were obtained at the liquid-to-solid ratio (L/s) of 100 mL/g, temperature of 30 ◦C, time of 20 min, and water content in DES (WC%) of 10% v/v. Arabinose, xylose, mannose, glucose, and galactose were found in extracted polysaccharides with molar ratios of 1.00:1.21:0.83:4.09:2.35. Six assays for antioxidant capacity and four extraction methods (ultrasonic, microwave, maceration, and Soxhlet) were compared, and ultrasonic extraction had the best performance. Selected DES solvents (choline chloride-lactic acid) were compared with conventional solvents such as methanol, ethanol, acetone, and water. Improvement in extraction for this DES to conventional solvents was between 70-237%.