Structural Identification and Antioxidant Activity of Pine Nut Peptide-Zinc Chelate Complex

To achieve the high-value utilization of pine nut resources, a novel zinc supplement was developed in this study. Pine nut protein was enzymatically hydrolyzed to prepare pine nut peptides (PP), which were subsequently chelated with zinc ions to form pine nut peptide-zinc chelate (PZn). Under optimized conditions, the zinc chelation rate of PZn reached 60.18 ± 1.77%. Peptidomic analysis revealed that PZn is composed of a select group of peptides predominantly characterized by low molecular weight (80.65 ± 1.47% < 1 kDa) and enrichment in aspartic acid, glutamic acid, and cysteine, indicating a self-selective chelation process. Comprehensive characterization via multiple techniques confirmed that zinc ions coordinate with carboxyl, hydroxyl, and thiol groups on these peptides, leading to charge neutralization, disruption of hydrogen-bonding networks, and peptide aggregation. Furthermore, bioactivity prediction of the PZn-constituting peptides revealed high intrinsic antioxidant potential, which corroborated the experimental results, showing that PZn exhibited significantly enhanced radical scavenging capacity compared to PP. These findings demonstrate that PZn possesses excellent zinc-binding capability and antioxidant activity, suggesting its potential as a novel zinc supplement, with its efficacy rooted in its specific molecular composition.