Effects of different chemical modifications on physicochemical and antioxidation properties of Lycium barbarum seed dreg polysaccharides

Recent studies have witnessed that chemical modification can improve the physicochemical and functional properties of plants' polysaccharides. Herein, we modified the natural Lycium barbarum seed dreg polysaccharides (LBSDPs) by sulfation (S-LBSDPs), phosphorylation (P-LBSDPs), and carboxymethylation (C-LBSDPs), and evaluated the chemical composition and antioxidant activity of their derivatives. Natural polysaccharides and their derivatives exhibited typical polysaccharide absorption peaks and characteristic group absorption peaks in FT-IR spectra along with maximum UV absorption. After modification, the total sugar and protein contents of the derivatives were decreased, whereas the uronic acid content was increased. Among the three derivatives, sulfated polysaccharides displayed excellent thermal stability. S-LBSDP and P-LBSDP showed the highest ABTS radical scavenging and reducing power while S-LBSDPs and C-LBSDPs showed better DPPH radical scavenging effect, and P-LBSDPs showed considerable Fe 2+ chelating ability. Our data indicate that chemical modifications can impart a positive effect on the antioxidant potential of plant-derived polysaccharides.