Identification of zinc‐chelating pumpkin seed (Cucurbita pepo L.) peptides and in vitro transport of peptide–zinc chelates

Abstract

In this study, pumpkin seeds peptide was purified, characterized, and evaluated for their zinc‐chelating capability, as well as in vitro bioaccessibility and transportation. Raw pumpkin seeds protein hydrolysate (PSPH) was produced by papain hydrolysis. The peptide fractions with the highest zinc‐chelating abilities were purified using immobilized metal affinity chromatography (IMAC) followed by gel filtration chromatography (GF). Eight peptides were identified, two of which with the lowest molecular weights were synthesized (RPKHPLK and RPKHPLSHDL) for determining potential bioaccessibility and bioavailability. Our results showed that the gastrointestinal stability of RPKHPLK‐Zn and RPKHPLSHDL‐Zn was higher than that of inorganic zinc salts in the simulated gastrointestinal tract model. Furthermore, the influence of the peptide zinc chelates on zinc transport was explored in vitro using Caco‐2 cell monolayer model. It was also shown that both RPKHPLK‐Zn and RPKHPLSHDL‐Zn could increase zinc transport rate and may be used to facilitate effective zinc absorption. The result of this study may provide important implications for developing plant protein foods with higher nutritional value. Practical Application As a potential alternative protein source, pumpkin seeds may find promising applications in plant‐based foods and drinks to meet the growing market for nonanimal foods. In this study, pumpkin seed protein peptides were prepared and purified, and the zinc‐chelating peptides were identified and evaluated for the abilities to promote the uptake of zinc. This type of mineral peptide chelates could be incorporated into plant‐based foods to increase mineral contents, which is significantly higher in foods originated from animals. The result of our study may provide important information for food industry to increase the nutritional value of plant‐based foods.

Dietary zinc supplements: beneficial health effects and application in food, medicine and animals

“…They can be used to assess the bioavailability of zinc in peptide-zinc complexes. 77 Wang synthesized a novel zinc-chelated sea cucumber synthetic peptide (SCSP), and the SCSP-Zn complex could be successfully transported through the intestinal capsule of ectopic rats as well as the intestinal membrane of Caco-2 cells, where the zinc transport reached 0.0014 mg mL −1 carried by SCSP. 86 The side chains of the peptide's amino acid residues and the zinc ions combine to produce the peptide-zinc complex.…”

The Molecular Basis for Zinc Bioavailability

“…Several bioactive peptides, which are resistant to hydrolysis and too large to be transported via amino acid transporters, are also capable of increasing the cellular uptake of zinc from cell culture media [ 89 , 90 , 91 ]. Alternatively, it is plausible that soluble zinc-binding ligands in the chyme, within an appropriate range of affinities for zinc, would increase zinc absorption by creating an affinity gradient towards zinc delivery to the active sites of zinc transporters [ 27 ].…”

Utilization of pumpkin, pumpkin powders, extracts, isolates, purified bioactives and pumpkin based functional food products: A key strategy to improve health in current post COVID 19 period: An updated review

“…Different peptides from pumpkin seed proteins were purified, characterized and evaluated for their zinc-chelating capability. Effective zinc transportation and absorption in gastrointestinal tract was observed in an in-vitro study experimenting on the pumpkin seed peptide-zinc chelates ( Peng et al, 2022 ). Pumpkin seed protein isolates were treated with high intensity ultrasonic treatment to improve the physicochemical, structural and foaming properties of protein isolates.…”