Preparation, In vitro evaluation of calcium transport, and chelation mechanism of rice bran peptide-calcium chelate

Peptide-calcium chelates have been shown to enhance calcium absorption. In this study, rice bran peptide-calcium chelate (RBP-Ca) was synthesized from rice bran protein, and its calcium transport efficiency was evaluated using a Caco-2 monolayer cell model. Additionally, the chelation mechanism of RBP-Ca was explored. Results indicated that alcalase was the optimal enzyme for producing RBP-Ca, yielding a calcium-binding capacity of 102.42 mg/g. Furthermore, RBP-Ca significantly increased calcium transport, with a transport amount 2.49-fold higher than that of CaCl₂ at a concentration of 0.1 mg/mL. X-ray diffraction (XRD) and particle size distribution analysis revealed that a chemical reaction occurred between the peptide and CaCl₂, resulting in the formation of chelates with larger particle sizes. Ultraviolet–visible (UV–vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and Zeta potential measurements suggested that the carboxyl and amide groups of the rice bran peptide (RBP) interact with calcium during chelation. Amino acid composition and liquid chromatography-tandem mass (LC-MS/MS) analysis indicated that aspartic acid (Asp) and glutamic acid (Glu) played crucial roles in the chelation process. These research findings provide a scientific basis for the development of efficient calcium supplements and the enhanced utilization of rice bran protein.