Summary
In this study, a promising nanoparticle of casein peptide–zinc chelate (CNP‐Zn) for zinc supplementation was obtained. The structure properties and transepithelial transport mechanism were investigated. The amino acid composition, particle size, zeta potential and microstructure were significantly changed after chelation with zinc ions. The results of fourier‐transform infrared spectroscopy suggested that the oxygen atoms from both the carboxyl and carbonyl groups, amides, were responsible for zinc chelation. After gastrointestinal digestion, over 40% of zinc remained bound in CNP–Zn. The transepithelial transport results showed that paracellular route and PepT1 transporter were involved in the absorption of CNP–Zn, and almost 50% of the bound zinc was co‐transported with peptides. These findings would provide a relatively comprehensive cognition for developing efficient dietary zinc carriers.
Casein-derived peptides are recognized as promising candidates for improving zinc bioavailability through the form of a peptide-zinc chelate. In the present work, a novel 11-residue peptide TEDELQDKIHP identified from casein hydrolysate in our previous study was synthesized to investigate the zinc chelation characteristics. Meanwhile, the digestion stability and transepithelial transport of TEDELQDKIHP-Zn were also investigated. The obtained results indicated that the carboxyl groups (from Asp and Glu), amino groups (from Lys and His), pyrrole nitrogen group of Pro, and imidazole nitrogen group of His were responsible for zinc chelation. The complexation with zinc resulted in a more ordered structure of TEDELQDKIHP-Zn. In terms of digestion stability, the chelate of TEDELQDKIHP-Zn could remain stable to a large extent after gastric (78.54 ± 0.14%) and intestinal digestion (70.18 ± 0.17%). Moreover, TEDELQDKIHP-Zn was proven to be a well-absorbed biological particle with a P app value higher than 1 × 10 −6 cm/s, and it could be transported across the intestine epithelium through transcytosis. TEDELQDKIHP-Zn exhibited more bioavailable effects on zinc absorption and ALP activity than inorganic zinc sulfate.
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