Ultrasound-assisted deep eutectic solvent extraction of Moringa oleifera leaf polysaccharides: process optimization, purification, physicochemical characterization, and bioactivities.

Ultrasound-assisted deep eutectic solvent (DES) extraction was developed for the efficient recovery of polysaccharides from Moringa oleifera leaves. Among seven DES systems, choline chloride-urea exhibited the highest extraction efficiency. Response surface methodology further optimized the extraction conditions, achieving a maximum polysaccharide yield of 17.1 %. The crude polysaccharide fraction (MOLP) was subsequently purified by DEAE-52 ion-exchange chromatography and Sephadex G-100 gel filtration, yielding two major purified fractions, MOLPs0 and MOLPs0.5. Structural characterization showed that MOLPs0 was a glucose-dominated neutral polysaccharide fraction, whereas MOLPs0.5 was an acidic heteropolysaccharide enriched in rhamnose and uronic acids. GPC, monosaccharide composition, FT-IR, SEM, AFM, and XRD analyses revealed clear differences in molecular weight distribution, charge properties, surface morphology, and supramolecular organization among the fractions. Bioactivity assays further demonstrated structure-dependent functional differences. Crude MOLP exhibited stronger antioxidant activity and α-glucosidase inhibitory activity, which may be associated with its structural heterogeneity and compositional complexity. In contrast, MOLPs0.5 showed relatively stronger pancreatic lipase inhibitory activity, possibly related to its acidic characteristics and higher uronic acid content. These results suggest that ultrasound-assisted DES extraction combined with chromatographic purification provides an effective strategy for obtaining structurally distinct Moringa oleifera leaf polysaccharides with different functional properties, supporting their potential application as functional food or nutraceutical ingredients.