Abstract: This study prepared lactopontin-derived peptides (L-OPN-P) by digesting lactopontin (L-OPN) in a dynamic in vitro digestion system simulating the gastrointestinal environment of 1 to 3-year-old infants, followed by desalting. The calcium-chelating capacity and intestinal calcium transport-promoting activity of L-OPN-P were systematically investigated. Results indicated that under simulated intestinal conditions, L-OPN-P exhibited excellent calcium-chelating capacity. The resulting chelate lactopontin peptide-chelated calcium (L-OPN-P-Ca) exhibited obviously increased particle size and zeta potential compared with L-OPN-P. Amino acid analysis revealed that the relative contents of aspartic acid (Asp), threonine (Thr), serine (Ser), and glutamic acid (Glu) in L-OPN-P-Ca were significantly increased compared with L-OPN-P. Ultraviolet (UV) and Fourier transform infrared spectroscopy (FTIR) revealed that calcium ions formed stable chelates with L-OPN-P through coordination with carboxyl oxygen and amino nitrogen atoms. Scanning electron microscopy (SEM) observations provided further confirmation of this chelation reaction. In a Caco-2 cell model simulating intestinal calcium transport, the amounts of calcium transported by L-OPN-P and L-OPN-P-Ca at 180 min reached (54.10 ± 0.33) and (62.93 ± 3.03) µg/well, respectively, indicating that both exhibited prominent intestinal calcium absorption-promoting activity, and the promoting effect of L-OPN-P-Ca was more significant. This study provides an important theoretical basis and innovative directions for the application of L-OPN in infant formula, as well as the development of novel efficient calcium supplements for infants.

Key words: lactopontin; in vitro dynamic digestion; lactopontin-derived peptides; peptide-calcium chelate; characterization; calcium absorption-promoting activity