Optimization of ultrasound-assisted extraction of purple yam polysaccharides using density-regulated natural deep eutectic solvents.

Abstract

This study developed and optimized an ultrasound-assisted extraction strategy using density-regulated natural deep eutectic solvents (NADES) for the extraction and recovery of purple yam polysaccharides (PYP). A choline chloride-citric acid-based NADES system was optimized through single-factor experiments combined with Plackett-Burman screening and Box-Behnken designing. The optimal extraction conditions were determined as follows: NADES molar ratio of 1:3, water content of 10 %, liquid-to-solid ratio of 20 mL/g, ultrasonication time of 40 min, at a power of 480 W with temperature of 40 °C. Polysaccharides were subsequently recovered by precipitation with 50 % (v/v) ethanol for 12 h. Under these conditions, the crude PYP yield reached 59.6 ± 0.6 mg/g with a PYP recovery of 29.14 ± 0.4 mg/g, significantly surpassing conventional methods. Molecular dynamics simulations revealed the extraction mechanism of the ChCl-CA-based NADES system and confirmed strong electrostatic interactions between the NADES and PYP, with an interaction energy of -23.53 kcal/mol (-1.0204 eV) In vitro antioxidant assays demonstrated that NADES-extracted PYP possessed pronounced antioxidant capacity, with radical-scavenging rates of 68.56 % for DPPH, 66.22 % for ABTS, and 61.06 % for hydroxyl radicals. Collectively, this work established an efficient, eco-friendly strategy for PYP isolation, providing theoretical foundations and technical references for the further development and practical utilization of purple yam polysaccharides.

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