Egg-White-Derived Antioxidant Peptide as an Efficient Nanocarrier for Zinc Delivery through the Gastrointestinal System

An antioxidant peptide derived from egg white, Asp-His-Thr-Lys-Glu (DHTKE), possesses specific amino acids related to zinc delivery. This study aimed to demonstrate the molecular basis of interactions between the egg white peptide (DHTKE) and zinc ions and investigate the effect of the DHTKE–Zn complex on zinc delivery through the gastrointestinal system. Approximately one DHTKE molecule can bind one zinc ion (n = 1.048 ± 0.085) through its carboxyl, amino, and imidazole nitrogen groups on Asp, His, and Glu. The formed DHTKE–Zn complex presented uniformly distributed globular particles with a particle size of 100–500 nm and underwent dissociation and re-chelation during gastrointestinal digestion. Moreover, the DHTKE peptide mostly remained stable, with a retention rate of 98.32% under gastrointestinal digestion, although one degradation product (DHTK) was identified by nanoscale liquid chromatography–electrospray ionization–tandem mass spectrometry in the gastrointestinal digests; the effectiveness of DHTKE–Zn digests on enhancing absorption of zinc was comparable to that of the initial complex.