Moringa oleifera Lam. Leaf Peptide–Calcium Chelates: Structural Characterization, Stability and Calcium Absorption-Promoting Transport Capability

A novel calcium-chelating peptide, KTFQGPPHG, was identified and screened from Moringa oleifera Lam. leaf protein hydrolysate, and further used to prepare a highly stable peptide–calcium chelate (KTFQGPPHG-Ca). The structure of KTFQGPPHG-Ca was characterized, while assessing its chelation stability and calcium transport potential. It was found that the calcium binding capacity of KTFQGPPHG reached 62.401 µg/mg. After chelation with calcium, KTFQGPPHG transitioned from an amorphous structure to a stable crystalline form. Carboxyl oxygen atoms and amino nitrogen atoms on KTFQGPPHG served as binding sites for Ca2+. The KTFQGPPHG-Ca demonstrates excellent phosphate stability and thermal stability. In addition, the calcium transport amount of KTFQGPPHG at 30 min and 60 min was significantly higher than that of the CaCl2 group (p < 0.05). Particularly, the calcium transport capacity at 30 min was 1.40-fold that of the CaCl2 group. KTFQGPPHG effectively counteracted the suppressive impact of dietary factors on Ca2+ absorption, and likely promoted Ca2+ translocation via the TRPV6 calcium channel pathway. The present results offer a theoretical basis for KTFQGPPHG-Ca to serve as a promising calcium source to improve intestinal calcium absorption.