Effects of Zinc Modification on the Antioxidant Activity and Bioaccessibility of Dictyophora indusiata Polysaccharide-Zn Complexes.

Polysaccharide-zinc complexes have been investigated as food-derived antioxidants and mineral carriers, but their performance depends on the degree of metal modification. In this study, Dictyophora indusiata polysaccharide (DP)-zinc preparations (DP-Zn) were produced at different initial Zn2+:DP feed ratios, and inductively coupled plasma optical emission spectrometry (ICP-OES) quantified the zinc content of optimized DP-Zn-1 as 1.04% (w/w). High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) showed that purified DP contained fucose, galactose, glucose, xylose, and glucuronic acid at a molar ratio of 1.00:6.69:1.85:3.52:2.24. In parallel 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) comparisons, moderate zinc modification (DP-Zn-1) produced the highest radical-scavenging activity, whereas excessive zinc feeding promoted aggregation and reduced activity. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) mapping showed Zn distributed across the C/O-rich matrix of DP-Zn-1, while the over-modified precipitate and DP + ZnSO4 physical mixture displayed distinct morphology and elemental-distribution patterns. In H2O2-treated HFF-1 human foreskin fibroblasts, DP-Zn-1 significantly improved cell viability relative to the corresponding Zn2+ control and reduced intracellular reactive oxygen species (ROS), although concentration-dependent cytotoxicity was observed at higher doses. During simulated digestion, 47.57% of the zinc became filterable by the end of the gastric stage, leaving 52.43% in the unreleased/non-filterable fraction; filterable zinc reached 49.75% at the end of the intestinal stage. These findings indicate that optimizing zinc modification is necessary to balance radical-scavenging activity, structural accessibility, digestion stability, and safety.