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

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 β-Dglucopyranosyl 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 β-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.