Polysaccharide from Thymelaea hirsuta L. leaves: Structural characterization, functional properties and antioxidant evaluation.

ABSTRACT

In this study, we successfully extracted a new polysaccharide from Thymelaea hirsuta L., which we named THP, with a yield of 13.94 % through aqueous extraction. The polysaccharide comprises 46.83 % neutral sugars and 7.08 % uronic acids. This heteropolysaccharide contains glucose, glucuronic acid, rhamnose, arabinose, and galactose with relative molar ratios of 29.68 25.73 21.31 13.47 and 9.8, respectively. Analysis of glycosylation positions via methylation and structural features using Fourier transform infrared (FT-IR) and solid-state nuclear magnetic resonance (ssNMR) spectroscopy revealed that THP has a repeating unit (1 → 3 and 1 → 4)-linked ß-d-glucopyranosyl backbone, with the d-glucopyranosyl residue as the branch point at O-6. The scanning electron microscopy (SEM) examination showed ellipsoidal granules with smooth surface. This polysaccharide also has good foaming capacity and emulsion stability, and a water holding capacity of 1.81 g/g. The THP dispersion at 1 % showed shear thinning behavior, demonstrating that it is a promising natural additive in various food formulations. The polysaccharide also demonstrated significant antioxidant properties, with a total antioxidant capacity of 315 mg α-tocopherol equivalents/g and an IC50 value of 8.01 mg/mL using the ß-carotene bleaching method, surpassing those of synthetic antioxidants. Additionally, when added at a concentration of 0.13 % to an oil/water emulsion system, THP effectively delayed lipid oxidation during storage at 37 °C. The kinetic study of THP-stabilized oil/water emulsion is anticipated to provide valuable insights for its future applications in food and pharmaceutical emulsions.