Preparation and Evaluation of the Chelating Nanocomposite Fabricated with Marine Algae Schizochytrium sp. Protein Hydrolysate and Calcium

Recent advance of physicochemical, structural properties, potential health benefits and application of bioactive macromolecules from Porphyra haitanensis: A review

Porphyra haitanensis (P. haitanensis) belongs to the class Rhodophyta and the family Bangiaceae, which is a unique artificially cultivated seaweed in China, especially in the coastal areas of Fujian and Zhejiang province. P. haitanensis is rich in amino acids, mineral elements, proteins, polysaccharides, and trace elements, with proteins and polysaccharides being the main components. P. haitanensis proteins and polysaccharides have variety of biological activities, including antioxidant, anticancer, immunomodulatory, anti-allergic and anti-aging activities, among others. This review introduced and summarized the preparation, isolation and purification, phytochemistry and structural properties, and biological activities of P. haitanensis proteins and polysaccharide, as well as their biomedical and food applications. Furthermore, a thorough analysis of the current trends and perspectives on P. haitanensis bioactive macromolecules were highlighted and prospected. Hopefully, this review can provide a useful reference value for the development and application of P. haitanensis bioactive macromolecules in the field of biomedical and food in the future.

Sustainability in the green engineering of nanocomposites based on marine-derived polysaccharides and collagens: A review

Nanocomposites are sophisticated materials that incorporate nanostructures into matrix materials, such as polymers, ceramics and metals. Generally, the marine ecosystem exhibits severe variability in terms of light, temperature, pressure, and nutrient status, forcing the marine organisms to develop variable, complex and unique chemical structures to boost their competitiveness and chances of survival. Polymers sourced from marine creatures, such as chitin, chitosan, alginate, sugars, proteins, and collagen play a crucial role in the bioengineering field, contributing significantly to the development of nanostructures like nanoparticles, nanocomposites, nanotubes, quantum dots, etc. These nanostructures offer a wide array of features involving mechanical strength, thermal stability, electrical conductivity, barrier and optical characteristics compared to traditional composites. Notably, marine nanocomposites have distinctive roles in a wide spectrum of applications, among them anti-cancer, anti-microbial, antioxidant, cytotoxic, food packing, tissue engineering and catalytic actions. Sol-gel, hot pressing, chemical vapor deposition, catalytic decomposition, dispersion, melt intercalation, in situ intercalative polymerization, high-energy ball milling and template synthesis are common processes utilized in engineering nanocomposites. According to our literature survey and the Web of Science, chitosan, followed by cellulose, chitin and MAPs emerge as the most significant marine polymers utilized in the construction of nanocomposites. Taken together, the current manuscript underscores the biogenesis of nanocomposites, employing marine polymers using eco-friendly processes. Furthermore, significant emphasis in this area is needed to fully explore their capabilities and potential benefits. To the best of our knowledge, this manuscript stands as the first comprehensive review that discusses the role of marine-derived polymers in engineering nanocomposites for various applications.

Preparation, Characterization and Stability of Calcium-Binding Peptides Derived from Chicken Blood

Calcium-binding peptides have gained significant attention due to their potential applications in various fields. In this study, we aimed to prepare, characterize, and evaluate the stability of calcium-binding peptides derived from chicken blood. Chicken hemoglobin peptides (CPs) were obtained by protease hydrolysis and were applied to prepare chicken hemoglobin peptide-calcium chelate (CP-Ca). The preparation conditions were optimized, and the characteristics and stability of CP-Ca were analyzed. The optimal chelating conditions were determined by single-factor and response surface tests, and the maximum calcium ion chelating rate was 77.54%. Amino acid analysis indicated that glutamic acid and aspartic acid motifs played an important role in the chelation of the calcium ions and CP. According to the characterization analysis, CP-Ca was a different substance compared with CP; calcium ions chelated CPs via the sites of carbonyl oxygen, carboxyl oxygen, and amino nitrogen groups; and after the chelation, the structure changed from a smooth homogeneous plate to compact granular. The stability analysis showed that CP-Ca was stable at different temperatures, pH, and gastrointestinal conditions. The study indicates that chicken blood is a promising source of peptide-calcium chelates, providing a theoretical basis for application in functional foods and improving the utilization value of chicken blood.

Novel strategy to the characterization and enhance the glycemic control properties of walnut-derived peptides via zinc chelation

This study aimed to utilize zinc coordination to promote the hypoglycemic and antioxidant properties of walnut-derived peptides, such as walnut protein hydrolysate (WPH) and Leu-Pro-Leu-Leu-Arg (LPLLR, LP5), of which LP5 was previously identified from WPH. The optimal conditions for the chelation were a peptide-to-zinc ratio of 6:1, pH of 9, duration of 50 min, and temperature of 50 °C. The WPH-Zn and LP5-Zn complexes increased the α-glucosidase inhibition, α-amylase inhibition, and antioxidant activity more than WPH and LP5 (p < 0.05). In particular, the antioxidant activity of WPH-Zn was superior to LP5-Zn. This is attributable to the WPH containing more aromatic amino acids, carboxylate groups and the imidazole groups, which implies its capacity to potentially coordinate with Zn2+ to form the WPH-Zn complex. Moreover, particle size, zeta potential, and scanning electron microscope indicated that the chelation of Zn2+ by peptides led to intramolecular and intermolecular folding and aggregation.

Evaluating the capability of soybean peptides as calcium ion carriers: a study through sequence analysis and molecular dynamics simulations

Calcium homeostasis imbalance in the body can lead to a variety of chronic diseases. Supplement efficiency is essential. Peptide calcium chelate, a fourth-generation calcium supplement, offers easy absorption and minimal side effects. Its effectiveness relies on peptide's calcium binding capacity. However, research on amino acid sequences in peptides with high calcium binding capacity (HCBC) is limited, affecting the efficient identification of such peptides. This study used soybean peptides (SP), separated and purified by gel chromatography, to obtain HCBC peptide (137.45 μg mg-1) and normal peptide (≤95.78 μg mg-1). Mass spectrometry identified the sequences of these peptides, and an analysis of the positional distribution of characteristic amino acids followed. Two HCBC peptides with sequences GGDLVS (271.55 μg mg-1) and YEGVIL (272.54 μg mg-1) were discovered. Molecular dynamics showed that when either aspartic acid is located near the N-terminal's middle, or glutamic acid is near the end, or in cases of continuous Asp or Glu, the binding speed, probability, and strength between the peptide and calcium ions are superior compared to those at other locations. The study's goal was to clarify how the positions of characteristic amino acids in peptides affect calcium binding, aiding in developing peptide calcium chelates as a novel calcium supplement.

Glycated Walnut Meal Peptide-Calcium Chelates: Preparation, Characterization, and Stability

Finding stable and bioavailable calcium supplements is crucial for addressing calcium deficiency. In this study, glycated peptide-calcium chelates (WMPHs-COS-Ca) were prepared from walnut meal protein hydrolysates (WMPHs) and chitosan oligosaccharides (COSs) through the Maillard reaction, and the structural properties and stability of the WMPHs-COS-Ca were characterized. The results showed that WMPHs and COSs exhibited high binding affinities, with a glycation degree of 64.82%. After glycation, Asp, Lys, and Arg decreased by 2.07%, 0.46%, and 1.06%, respectively, which indicated that these three amino acids are involved in the Maillard reaction. In addition, compared with the WMPHs, the emulsifying ability and emulsion stability of the WMPHs-COS increased by 10.16 mg2/g and 52.73 min, respectively, suggesting that WMPHs-COS have better processing characteristics. After chelation with calcium ions, the calcium chelation rate of peptides with molecular weights less than 1 kDa was the highest (64.88%), and the optimized preparation conditions were 5:1 w/w for WMPH-COS/CaCl2s, with a temperature of 50 °C, a chelation time of 50 min, and a pH of 7.0. Scanning electron microscopy showed that the "bridging role" of WMPHs-COS changed to a loose structure. UV-vis spectroscopy and Fourier transform infrared spectrometry results indicated that the amino nitrogen atoms, carboxyl oxygen atoms, and carbon oxygen atoms in WMPHs-COS chelated with calcium ions, forming WMPHs-COS-Ca. Moreover, WMPHs-COS-Ca was relatively stable at high temperatures and under acidic and alkaline environmental and digestion conditions in the gastrointestinal tract, indicating that WMPHs-COS-Ca have a greater degree of bioavailability.

Preparation, characterization, and bioavailability evaluation of antioxidant phosvitin peptide-ferrous complex

BACKGROUND

Iron deficiency anemia (IDA) is one of the commonest global nutritional deficiency diseases, and the low bioavailability of iron is a key contributing factor. The peptide-iron complex could be used as a novel iron supplement to improve iron bioavailability.

RESULTS

In this study, antioxidant low molecular weight (<3 kDa) phosvitin peptide (named PP-4) was separated to prepare a phosvitin peptide-ferrous complex (named PP-4-Fe); then the structural conformation of PP-4-Fe was characterized and its bioavailability by in vitro digestion was evaluated. The results showed that PP-4 had good ferrous-binding activity with 96.14 ± 2.86 μg Fe2+ mg-1 , and had a strong antioxidant effect with 995.61 ± 79.75 μmol TE mg-1 in 2,2'-azinobis'3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 62.3 ± 3.95 μmol FeSO4 mg-1 in ferric ion reducing antioxidant power (FRAP). After ferrous binding, the FRAP activity of PP-4-Fe, enhanced by 1.8 times, formed a more ordered structure with an increase in α-helix and decrease in γ-random coil. The ferrous binding sites of PP-4 involved were the amino, carboxyl, imidazole, and phosphate groups. The PP-4-Fe complex displayed excellent gastrointestinal stability and antioxidant effects during digestion. The iron dialysis percentage of PP-4-Fe was 74.59% ± 0.68%, and increased to 81.10% ± 0.89% with the addition of 0.25 times vitamin C (VC). This indicated that PP-4-Fe displayed excellent bioavailability and VC in sufficient quantities had a synergistic effect on improving bioavailability.

CONCLUSIONS

This study demonstrated that antioxidant phosvitin peptide was an efficient delivery system to protect ferrous ions and suggested that the phosvitin peptide-ferrous complex has strong potential as a ferrous supplement. © 2023 Society of Chemical Industry.

A critical review of a typical research system for food-derived metal-chelating peptides: Production, characterization, identification, digestion, and absorption

In the past decade, food-derived metal-chelating peptides (MCPs) have attracted significant attention from researchers working towards the prevention of metal (viz., iron, zinc, and calcium) deficiency phenomenon by primarily inhibiting the precipitation of metals caused by the gastrointestinal environment and exogenous substances (including phytic and oxalic acids). However, for the improvement of limits of current knowledge foundations and future investigation directions of MCP or their derivatives, several review categories should be improved and emphasized. The species' uniqueness and differences in MCP productions highly contribute to the different values of chelating ability with particular metal ions, whereas comprehensive reviews of chelation characterization determined by various kinds of technique support different horizons for explaining the chelation and offer options for the selection of characterization methods. The reviews of chelation mechanism clearly demonstrate the involvement of potential groups and atoms in chelating metal ions. The discussions of digestive stability and absorption in various kinds of absorption model in vitro and in vivo as well as the theory of involved cellular absorption channels and pathways are systematically reviewed and highlighted compared with previous reports as well. Meanwhile, the chelation mechanism on the molecular docking level, the binding mechanism in amino acid identification level, the utilizations of everted rat gut sac model for absorption, and the involvement of cellular absorption channels and pathway are strongly recommended as novelty in this review. This review makes a novel contribution to the literature by the comprehensive prospects for the research and development of food-derived mineral supplements.

Characterization of Oyster Protein Hydrolysate-Iron Complexes and their In Vivo Protective Effects against Iron Deficiency-Induced Symptoms in Mice

Iron is one of the trace mineral elements, and iron deficiency is a common phenomenon that negatively influences human health. Food-derived iron supplements were considered excellent candidates for improving this syndrome. In this work, oyster-protein hydrolysates (OPH) and ferrous chloride successfully formed the OPH-Fe complex (6 mg/mL, 40 °C, 30 min), where the main binding sites involved were the carboxyl and amino groups. The OPH-Fe complex showed no obvious changes in the secondary structure, while the iron changed the morphological appearance and also showed fluorescence quenching, an ultraviolet shift, and an increase in size distribution. The OPH-Fe complex showed better dynamic absorption of iron (64.11 μmol/L) than ferrous sulfate (46.90 μmol/L), and the medium dose had better protective effects against iron-deficiency anemia in vivo. Three representative peptides (DGKGKIPEE, FAGDDAPRA, and VLDSGDGVTH) that were absorbed intact were identified. This experiment provided a theoretical foundation for further study of the digestion and absorption of the OPH-Fe complex.

Development, characterization and in vivo zinc absorption capacity of a novel soy meal hydrolysate-zinc complexes

Background

Zinc is an essential trace element for the human body. Recently, a novel Zn-binding peptide, Lys-Tyr-Lys-Arg-Gln-Arg-Trp (PP), was purified and identified from soy protein hydrolysates with high Zn-binding capacity (83.21 ± 2.65%) by our previous study. The preparation of soy meal hydrolysates (SMHs)-Zn complexes is convenient and low-cost, while PP (Lys-Tyr-Lys-Arg-Gln-Arg-Trp)-Zn complexes have a higher coordination rate but a relatively high cost. The aim of this study was to investigate the effect of soy meal hydrolysates (SMHs)-Zn complexes on zinc absorption in mice model, and synthetic soy peptide (PP)-Zn complexes with high Zn-binding capacity were used as control. Firstly, SMHs were prepared by enzymolysis, and the PP (Lys-Tyr-Lys-Arg-Gln-Arg-Trp) were synthesized based on previous studies. The binding mechanism of soy hydrolysates and zinc was analyzed by spectral analysis. Furthermore, the cytotoxicity of the SMHs-Zn complexes was also studied using the CCK-8 method. The effect of zinc absorption was evaluated based on Zn content, total protein and albumin content, relevant enzyme system, and the PeT1 and ZnT1 mRNA expression levels.

Result

The result showed that zinc was bound with carboxyl oxygen and amino nitrogen atoms on SMHs, with hydrophobic and electrostatic interactions as auxiliary stabilizing forces. SMHs-Zn were proved to have great solubility and a small particle size at different pH values, and it showed a beneficial effect on Caco-2 cells growth. Moreover, it was proved that SMHs-Zn and PP-Zn could increase the levels of zinc and the activity of Zn-related enzymes in mice. SMHs-Zn possessed higher PepT1 and ZnT1 mRNA expression levels than PP-Zn in the small intestine.

Conclusion

SMHs-Zn with a lower Zn-binding capacity had similar effects on zinc absorption in mice as PP-Zn, suggesting that the bioavailability of peptide-zinc complexes in mice was not completely dependent on their Zn-binding capacity, but may also be related to the amino acid composition.

Novel Casein-Derived Peptide-Zinc Chelate: Zinc Chelation and Transepithelial Transport Characteristics

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.

Millet bran protein hydrolysates derived peptides-zinc chelate: Structural characterization, security prediction in silico, zinc transport capacity and stability against different food processing conditions

A novel peptide Ser-Asp-Asp-Val-Leu (SDDVL) of excellent zinc-chelating capacity (13.77 mg/g) was identified in millet bran protein hydrolysates. In silico prediction demonstrated that SDDVL had no potential toxicity. The results of structural characterization demonstrated that both amino group and carboxyl group of SDDVL were the primary zinc-chelating sites. Moreover, SDDVL-zinc chelate showed higher stability (p < 0.05) than ZnSO₄ and zinc gluconate under different processing conditions including most pasteurization conditions, heating at 100°C for 10-50 min, various pH values (8.0-10.0), treatment of glucose (4-8 g/100 g) or NaCl (1-4 g/100 g), and simulated gastrointestinal digestion. In addition, SDDVL-zinc chelate showed higher zinc transport capacity than ZnSO₄ and zinc gluconate in Caco-2 cells (p < 0.05). These results suggested that millet bran peptide had a positive effect on the gastrointestinal stability and bioavailability of Zn, and SDDVL-zinc chelate could be used as ingredient of zinc supplements. PRACTICAL APPLICATION: The current study provided a practical method to identify peptides of excellent zinc-chelating capacity from millet bran protein hydrolysates. This study demonstrated that in silico prediction assisted with suitable database was a fast, practical, and economic way to evaluate the security and to analysis the physicochemical properties of novel peptides. Moreover, it provided an efficient method to assess the stability of peptide-zinc chelate under different food processing conditions, which was the theoretical basis for utilization of peptide as ingredient of zinc fortifications.

Isolation, Purification and Structure Identification of a Calcium-Binding Peptide from Sheep Bone Protein Hydrolysate

To isolate a novel peptide with calcium-binding capacity, sheep bone protein was hydrolyzed sequentially using a dual-enzyme system (alcalase treatment following neutrase treatment) and investigated for its characteristics, separation, purification, and structure. The sheep bone protein hydrolysate (SBPH) was enriched in key amino acids such as Gly, Arg, Pro, Leu, Lys, Glu, Val, and Asp. The fluorescence spectra, circular dichroism spectra, and Fourier-transform infrared spectroscopy results showed that adding calcium ions decreased the α-helix and β-sheet content but significantly increased the random and β-turn content (p < 0.05). Carboxyl oxygen and amino nitrogen atoms of SBPH may participate in peptide−calcium binding. Scanning electron microscopy and energy dispersive spectrometry results showed that SBPH had strong calcium-chelating ability and that the peptide−calcium complex (SBPH−Ca) combined with calcium to form a spherical cluster structure. SBPH was separated and purified gradually by ultrafiltration, gel filtration chromatography, and reversed-phase high-performance liquid chromatography. Liquid chromatography-electrospray ionization/mass spectrometry identified the amino acid sequences as GPSGLPGERG (925.46 Da) and GAPGKDGVRG (912.48 Da), with calcium-binding capacities of 89.76 ± 0.19% and 88.26 ± 0.25%, respectively. The results of this study provide a scientific basis for the preparation of a new type of calcium supplement and high-value utilization of sheep bone.

Formulation of Novel Composite (Activated Nanoclay/Hydrocolloid of Nostoc sphaericum) and Its Application in the Removal of Heavy Metals from Wastewater

The removal of heavy metals from wastewater is an environmental challenge which demands the use of environmentally friendly materials that promote a circular economy. This study aimed to apply a novel composite of an activated nanoclay/hydrocolloid in the removal of heavy metals from wastewater. A composite blended under pressure was prepared with spray-dried hydrocolloid derived from Nostoc sphaericum algae and activated nanoclay in an acid medium and 1M NaCl. The composite and components were analyzed through infrared (IR), X-ray (XR), ζ potential, cation exchange capacity (CEC), particle size, and SEM images. The composite was subjected to the adsorption of heavy metals (Pb, As, Zn, and Cd) at pH 4.5 and the removal percentage, kinetics, and adsorption isotherms were evaluated. It was observed that the activated nanoclay and the composite that presented a particle size of around 400 nm significantly increased (p-value < 0.05) the CEC, ζ potential, the functional groups, and chelating components, removing heavy metals above 99% for Pb, As 33%, Cd 15%, and Zn 10%. Adsorption kinetics was adjusted to the pseudo second-order model (R2 > 0.98), and the Langmuir and Freundlich models better represented the sorption isotherm at 20 °C. The formulated composite presents a good ability to remove heavy metals in wastewater.

Preliminary Characterization of a Spray-Dried Hydrocolloid from a High Andean Algae (Nostoc sphaericum)

The search for new natural sources of hydrocolloids with stabilizing, thickening, and good binding capacity, from raw materials that are environmentally friendly and that contribute to the circular economy is a challenge for the food industry. The aim of the study was the preliminary characterization of a spray-dried hydrocolloid from high Andean algae Nostoc sphaericum. Four ecotypes of algae from Peruvian high Andean lagoons located above 4000 m were considered. The samples were collected in the period March−April 2021 and were subjected to a spray drying process in an aqueous medium. The characterization showed that the dehydrated nostoc ecotypes presented high protein and carbohydrate content, making it a potential material for direct use as a functional food for humans. The spray-dried product presented good stability for its use as a hydrocolloid, with zeta potential values (ζ), around 30 mV, evidencing the presence of -CO-, -OH, -COO-, and -CH groups, characteristic of polysaccharides, representing 40% of total organic carbon on average, giving it low water activity values and particle size at the nanometric level. Major minerals such as Ca (>277 mg/100 g), Mg (>19.7 mg/100 g), and Fe (>7.7 mg/100 g) were reported. Spray-dried nostoc is a hydrocolloid material with high potential for the food industry, with good nutritional content and techno-functional behavior.

Discovery of calcium-binding peptides derived from defatted lemon basil seeds with enhanced calcium uptake in human intestinal epithelial cells, Caco-2

It is anticipated that calcium-chelating peptides may serve to enhance the absorption of calcium. This research examined defatted lemon basil seeds (DLBS) which had been treated with Alcalase under optimized parameters for the degree of hydrolysis for proteolysis, discovering that the activity for calcium-binding in a competitive condition with phosphate ion was 60.39 ± 1.545%. The purification of the hydrolysates was performed via ultrafiltration along with reversed-phase high performance liquid chromatography (RP-HPLC). Determination of the purified peptide amino acid sequence was confirmed for both peptides and reported as Ala-Phe-Asn-Arg-Ala-Lys-Ser-Lys-Ala-Leu-Asn-Glu-Asn (AFNRAKSKALNEN; Basil-1), and Tyr-Asp-Ser-Ser-Gly-Gly-Pro-Thr-Pro-Trp-Leu-Ser-Pro-Tyr (YDSSGGPTPWLSPY; Basil-2). The respective activities for calcium-binding were 38.62 ± 1.33%, and 42.19 ± 2.27%. Fluorescence spectroscopy, and fourier transform infrared spectroscopy were employed in order to assess the chelating mechanism between calcium and the peptides. It was found that the calcium ions took place through the activity of the amino nitrogen atoms and the oxygen atoms on the carboxyl group. Moreover, both of these peptides served to improve calcium transport and absorption in Caco-2 cell monolayers, depending on the concentration involved. It was revealed that the peptide-calcium complexes offered an increased calcium absorption percentage when compared to free calcium at similar concentrations. It might be concluded that the peptide within the peptide-calcium complex can promote calcium absorption through both active and passive transport pathways by increasing calcium concentration and promoting cell membrane interaction. Accordingly, DLBS protein can be considered a strong potential source of protein which can be used to produce calcium-binding peptides and might therefore play a role in the production of nutraceutical foods as a bioactive ingredient.

Identification and characterization of metal-chelating bioenhancer peptide derived from fermented Citrullus lanatus seed milk

In the present investigation, a metal-chelating bioactive peptide was derived from Citrullus lanatus seed milk fermented with Lactococcus lactis. The cationic fermented milk peptide (FMP) thus obtained was purified using the HiTrap-chelating column followed by rpHPLC. The FMP possessed the ability to chelate multiple divalent cations like Cu²⁺ , Ca²⁺ , and Fe²⁺ with 86.81%, 61.04%, and 24.32% of chelation respectively and further it exhibited 78.03% of DPPH free radical scavenging activity. Interaction of FMP with metal ions was assessed by change in the absorption spectra and was analyzed by ultraviolet-visible and fluorescence spectroscopy. The FMP-metal complexes were found stable at simulated gastric conditions. In vitro analysis using intestinal Caco-2 cell lines revealed that there was an increase in metal bioavailability in the presence of the FMP and was least influenced by the addition of a dietary inhibitor, phytic acid. By LC-MS analysis the molecular mass of FMP was found to be 11.6 kD and it contains oxygen-rich and nitrogen-rich amino acids that favor the metal chelation. In our study, we have found that the fermented C. lanatus seed milk can serve as a potential functional food with bioenhancer peptides that increase metal bioavailability and enhance human health. PRACTICAL APPLICATIONS: Chelated metals are preferred over non-chelated ones by most nutritionists for their better absorption rate. Chelation protects the minerals from the digestive process and increases their bioavailability. Fermentation with lactic acid bacteria produces bioactive peptides with metal-chelating and antioxidant ability which provides additional health benefits beyond supplying basic nutrients. Lactococcus lactis fermented milk acts as a probiotic product with bioenhancer peptide that increases mineral bioavailability. Consumption of metals in chelated form can reduce excess intake of metal. Fermented watermelon seed milk can be a promising probiotic drink rich in bioenhancer peptides and can enhance the bioavailability of divalent cations of a high therapeutic index.

Copper chelating protein hydrolysate from Salvia hispanica L. by pepsin-pancreatin treatment

Salvia hispanica L. (Chia) seeds are good source of proteins with diverse health benefits. The seed protein was extracted through alkaline solubilisation followed by acid precipitation to separate fibres and are digested sequentially by pepsin and pancreatin. Enzyme-substrate ratio, temperature and contact time had high impact on degree of hydrolysis affecting their chelating ability. Maximum degree of hydrolysis (14.06%) and maximum copper chelation (74.98%) was obtained at 4% w/w enzyme-substrate ratio at 37 °C for 4 h. Copper chelating enzymatic hydrolysate was isolated by HiTrap chelating column and purified further by rpHPLC. Out of nine fractions obtained by rpHPLC the sixth fraction with 93.09 ± 0.16% of copper chelating activity and 82.91 ± 0.52% of antioxidant activity was further characterized as Copper chelating Chia Protein Hydrolysate (CCPH). Ultraviolet spectroscopy and fluorescence spectroscopic studies revealed the interaction of the major chelating sites of the CCPH with the copper divalent ion. The purified CCPH was subjected to LC-MS/ESI-TOF analysis from which six major intense peaks obtained with m/z value ranging from 0.4 kDa to 2.5 kDa were identified and sequenced using Mascot database. The functional behaviour and the binding capacity of these peptides were analysed by their amino acid composition. The CCPH was stable in a simulated gastric condition and its chelating ability remained unaltered. These results explored an informative bioactive peptides with varied activity and one valuable among is the copper chelating with antioxidant property. Furthermore, these Chia seed protein hydrolysates can be useful as dietary supplements to enhance mineral bioavailability.

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Optimization of Pepsin-Pancreatin hydrolysis of Salvia hispanica L. (Chia) seed protein.

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Purification of Copper Chelating Protein Hydrolysate (CCPH) using affinity chromatography and rpHPLC.

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The structure-function analysis of purified CCPH by UV/Vis and Fluorescence spectroscopic analysis and mass determination by LC-MS/ESI-TOF.

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In vitro gastro-intestinal simulation studies of CCPH indicated its structural stability with constant chelating property.

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Hence CCPH can be a promising, safe alternative of metal salts for mineral fortification.

Preparation of dextran-casein phosphopeptide conjugates, evaluation of its calcium binding capacity and digestion in vitro

In order to construct a novel and efficient calcium delivery system, a dextran- casein phosphopeptide (CPP) conjugates as calcium carrier was prepared by Maillard reaction of CPP and dextran. The preparation of the conjugates, construction of calcium delivery system and digestion in vitro were studied. The grafting rate of conjugates, which was confirmed by migration and intensity changes in the characteristic peaks using ultraviolet-visible and Fourier transform infrared spectroscopy, reached 48.88%. The microscopy showed CPP was coated with dextran, the conjugates with a kind of "shell-core" structure had excellent stability. Compared with CPP, the chelating rate of conjugates increased from 6.0% to 13.87%, and the calcium retention rate improved from 1.09% to 7.90% in vitro digestion. The calcium binding capacity and effect of controlled release of the conjugates were superior to those of CPP. Therefore, the conjugates could be used as an effective carrier for new calcium supplements.

Novel Zn-Binding Peptide Isolated from Soy Protein Hydrolysates: Purification, Structure, and Digestion

In this study, a novel Zn-binding peptide, Lys-Tyr-Lys-Arg-Gln-Arg-Trp (KYKRQRW), was purified and identified from soy protein isolate hydrolysates (SPIHs). The Zn-binding peptide exhibited improved Zn-binding capacity (83.21 ± 2.65%) than SPIH solutions. CD, NMR, and Fourier transform infrared spectroscopy were used to confirm the complexation between Zn and the peptide. The results showed that the Zn-binding peptide formed a folding structure with part of the β-sheet (29.3-13.4%) turning into random coils (41.7-57.6%) during complexation. It was further proved that the binding sites were located at the oxygen atoms on the carboxyl group of the Trp side chain and nitrogen atoms on the amino group of the Lys side chain. Moreover, the Zn-peptide complex exhibited increased solubility than ZnSO₄ during simulated gastrointestinal digestion. This study highlighted that the novel soy peptide possessed a strong zinc chelate rate and had a positive effect on the gastrointestinal stability of Zn which could be utilized as a functional ingredient in future.

Effects of zinc sulfate and zinc lactate on the properties of tilapia (Oreochromis Niloticus) skin collagen peptide chelate zinc

In this study, the properties difference of Tilapia (Oreochromis Niloticus) skin collagen peptide chelate zinc prepared by zinc sulfate (P-Zn-S) and zinc lactate (P-Zn-L) were investigated. The results indicated that compared with P-Zn-L, P-Zn-S exhibited higher Zn-chelating capacity and different structural morphology, which may closely relate to the composition amino acid of Asp, Glu, His, Lys, Arg, Cys and Pro. FTIR and UV-Vis analysis indicated that different zinc sources could influence the metal ligands and the types of amino acid residues which were involved in chelation reaction. P-Zn-L exhibited better zinc solubility and had higher dialyzable zinc than P-Zn-S, indicating that P-Zn-L had better zinc bioaccessibility. These results suggested that P-Zn-L with a granular structure could reduced gastric stability, promoted intestinal release, and was beneficial to zinc absorption, which can be used as dietary zinc carriers.

Research progress on applications of calcium derived from marine organisms

Calcium is an important mineral that plays an integral role in human health, especially bone health. Marine biological calcium is an abundant resource that is generally accepted and has a complex active structure. This review evaluates research progress on marine biological calcium with regards to its sources, use of calcium supplements, calcium bioavailability, and novel applications of marine calcium. The potential for future development and the use of products incorporating marine biological calcium in biomedical research and the pharmaceutical, health care, and food industries are also reviewed. The goal of this review is to provide a comprehensive documentation on resource utilization and product development from marine organisms.

Investigating the calcium binding characteristics of black bean protein hydrolysate

The black bean protein has been widely utilized to prepare hydrolysates with different bioactive properties. Herein, we hydrolyzed the black bean protein to prepare hydrolysate with calcium binding activity and characterized its behavior. Our results showed that ficin was superior in obtaining hydrolysate with calcium binding capacity in comparison with trypsin, alcalase and bromelain. In particular, the optimal capacity of ficin hydrolysate reached 77.54 ± 1.61 μg mg-1, where the optimal hydrolysis conditions of ficin were a temperature of 70 °C, a pH value of 6.2, an enzyme concentration of 1.61% and a time of 3 h. This might be due to high proportions of aspartic acid and glutamic acid (35.59%). Further spectral analysis evidenced the formation of hydrolysate-calcium complexes, demonstrating that the interaction between hydrolysate and calcium ions primarily occur on carboxyl oxygen atoms and amino nitrogen atoms. These findings provide a possible utilization of black bean hydrolysate to serve as a calcium supplement nutraceutical to enhance the absorption and bioavailability.

Antarctic Krill Derived Nonapeptide as an Effective Iron-Binding Ligand for Facilitating Iron Absorption via the Small Intestine

A novel nonapeptide DTDSEEEIR identified from Antarctic krill (Euphausia superba) iron-binding peptides was used in this study to analyze its iron-binding sites and structural changes after iron coordination. The enzymatic resistance and transport of DTDSEEEIR-iron during gastrointestinal digestion and absorption as well as the relationship between the DTDSEEEIR stability and the enhancement of iron absorption were further explored. Results revealed that iron ions spontaneously bound to the carboxyl, hydroxyl, and amino groups of the DTDSEEEIR peptide, which induced the folding of DTDSEEEIR to form a more orderly structure. The DTDSEEEIR peptide remained stable to a certain extent (79.60 ± 0.19%) after gastrointestinal digestion and the coordination of iron improved the digestive stability of the DTDSEEEIR peptide (93.89 ± 1.37%). Moreover, the stability of DTDSEEEIR across intestinal epithelium had a positive effect on iron absorption, which implied that DTDSEEEIR might carry iron ions through intestinal epithelial cells.

Calcium Delivery System Assembled by a Nanostructured Peptide Derived from the Sea Cucumber Ovum

In this study, the binding mechanism, morphological, and conformational analysis of the complex of a sea cucumber ovum derived octapeptide (EDLAALEK) with Ca²⁺ as well as its calcium delivery behavior via the gastrointestinal (GI) tract were investigated. The Ca²⁺ specifically bound to two carboxyl oxygen atoms of C-terminal Glu and Asp on the EDLAALEK peptide at a stoichiometric ratio of 1:1. Calcium coordination induced the self-assembly of the EDLAALEK peptide, resulting in the formation of a nanocomposite with a crystal structure. Furthermore, the formed nanocomposite went through dissociation and self-assembly during in vitro GI digestion, accompanied by the release and rechelation of Ca²⁺, which was related to changes in their secondary structure. Nevertheless, the GI digests of the EDLAALEK-calcium complex could significantly enhance Ca²⁺ absorption across Caco-2 cell monolayers. The findings suggest that the sea cucumber ovum derived peptide has the potential as an efficient nanocarrier to transport calcium through the GI system.

Evaluation and structure-activity relationship analysis of antioxidant shrimp peptides

The effects of amino acids Gln and Lys on the antioxidant ability of peptides were investigated in this study. The identified peptides Lys-Met-Asp-Asp-Lys (KMDDK), Lys-Met-Asp-Asp-Gln (KMDDQ), Gln-Met-Asp-Asp-Lys (QMDDK), and Gln-Met-Asp-Asp-Gln (QMDDQ) were used to investigate their antioxidant activity and the structure-activity relationship by using UPLC-Q-TOF-MS, flow cytometry, laser scanning confocal microscopy and ¹H NMR spectroscopy. The results indicated that the four pentapeptides significantly increased the viability of PC12 cells and inhibited cell apoptosis and that QMDDQ possessed a stronger survival activity than the others in cell apoptosis. Moreover, the four peptides significantly decreased the scopolamine-induced ROS and LDH content in PC12 cells, and upregulated the SOD activity to the level of the scopolamine group. The DPPH and hydroxyl radical scavenging of QMDDQ were higher than those of the other peptides at 0.5 mg mL^-1 and 1.0 mg mL^-1 (P < 0.05). ¹H NMR spectra revealed that the prominent antioxidant ability of QMDDQ might be attributed to more active hydrogen sites and functional groups. The carboxyl active hydrogen atoms and amino active hydrogen atoms as active sites play a critical role in the antioxidant capacity.

Effect of duck egg white peptide-ferrous chelate on iron bioavailability in vivo and structure characterization

BACKGROUND

In order to utilize the industrial by-product 'salted duck egg white' as novel iron additives, the effects of desalted duck egg white peptides-ferrous chelate (DPs-Fe) on the promotion of iron uptake and the structure were investigated.

RESULTS

Different doses of DPs-Fe were given and iron sulfate (FeSO₄ ) was used as a positive control. After three weeks, hemoglobin (Hb), hematocrit (HCT), red blood cells (RBCs), mean corpuscular volume (MCV), serum iron (SI) and serum ferritin (SF) in iron-deficiency anemia (IDA) rats could be significantly (P < 0.05) increased to the normal levels by DPs-Fe. The gene expressions of divalent metal transporter 1 (DMT1), ferroportin 1 (FPN1) and Hepcidin could be regulated by DPs-Fe. Additionally, DPs-Fe was formed during the chelation process and the structure was characterized. Eight crucial iron-chelating peptides of duck egg white peptides (DPs) were identified by HPLC-ESI-MS/MS, such as Pro-Val-Glu-Glu and Arg-Ser-Ser. It indicated that Glu, Asp, Lys, His, Ser, Cys residues might play crucial roles in the chelating of DPs with iron.

CONCLUSION

DPs-Fe could be a potential iron supplement, and the Glu, Asp, Lys, His played important roles in binding iron and promoting iron uptake. This research expands the understanding of iron uptake by DPs and provides an opportunity for recycling a discarded processing byproduct. © 2018 Society of Chemical Industry.

Novel calcium-chelating peptides from octopus scraps and their corresponding calcium bioavailability

BACKGROUND

To reducing the massive marine pollution and resource waste caused by octopus scraps, we developed a novel octopus scraps protein hydrolysate (OSPH), which displays calcium-chelating activity, and we investigated the chelating interaction and calcium bioavailability of OSPH-Ca.

RESULTS

The structural properties of amido and carboxy groups indicated that they could be the reaction sites for chelation. The particle radius of OSPH increased by 32.25 nm after the calcium chelated with OSPH, indicating intramolecular and intermolecular folding and aggregating. The enthalpy of OSPH increased by 0.8323 after chelation, showing that bands of OSPH-Ca needed more thermal energy to be destroyed than OSPH. Meanwhile, the chelate showed remarkable stability and absorbability under either acidic or basic conditions, which favored calcium absorption in the gastrointestinal tracts of humans. The calcium intake of OSPH-Ca increased by 41% when compared with that of CaCl₂ . In particular, OSPH-Ca could protect calcium ions from precipitation caused by dietary inhibitors tannic acid and phytate, while calcium uptake efficiency remained at 3.35 and 1.68 times higher than that of CaCl₂ .

CONCLUSION

These findings revealed the feasibility of transforming octopus scraps into a novel functional calcium chelate based on peptides, promoting environmental sustainability. © 2018 Society of Chemical Industry.

Immunomodulatory effects of Pseudostellaria heterophylla peptide on spleen lymphocytes via a Ca2+/CaN/NFATc1/IFN-γ pathway

Screening and isolation of Pseudostellaria heterophylla peptide with immunomodulatory activity via a Ca²⁺/CaN/NFATc1/IFN-γ pathway.

The formation mechanism of a sea cucumber ovum derived heptapeptide–calcium nanocomposite and its digestion/absorption behavior

Calcium coordination induced the self-assembly of the sea cucumber ovum derived heptapeptide (NDEELNK), resulting in the formation of the nanocomposite with potential function to transport calcium through the gastrointestinal system.

The effect of dietary magnesium and caseinphosphopeptides on bone metabolism in rats

The effect of dietary magnesium (Mg) or caseinphosphopeptides (CPPs) on bone metabolism has been reported. However, few studies have investigated the effects of simultaneous supplementation of Mg and CPPs. Sixty-three 3-week-old Sprague-Dawley male rats were divided into seven groups and fed a specified diet for 45 days. Body characteristics, bone physicochemical indicators, and bone metabolism indicators relative to bone metabolism were analyzed. We found that, first, a dietary Mg deficiency resulted in increased bone formation and decreased bone resorption. Second, dietary Mg or CPP supplementation promoted bone formation and prevented bone resorption. Third, dietary Mg supplementation with CPPs also functioned to enhance bone formation and prevent bone resorption. There were synergistic effects on femur length, serum parathyroid hormone level and urinary deoxypyridinoline of the HS-Mg-CPP group (0.2% Mg, 0.1% CPPs). The increase in the femur length of the HS-Mg-CPP group compared with the control group was 6% which was much higher than that of HS-Mg (1%) or CPPs (5%). The induction in serum parathyroid hormone content in the HS-Mg-CPP group was 33% compared with the control group which was higher than that of the induction of the HS-Mg (19%) or CPP (23%) group. The induction in the deoxypyridinoline content of the HS-Mg-CPP (43%) group compared with the control group was remarkably higher than that of HS-Mg (8%) or CPPs (16%). Overall our results demonstrated that high doses of Mg (0.2%) and CPPs (0.1%) in combination produced synergistic effects on femur length, serum parathyroid hormone level and urinary deoxypyridinoline in rats, which is important for a better understanding of the effect of Mg and CPPs on bone metabolism.

In Vitro Antioxidant Activities of Enzymatic Hydrolysate from Schizochytrium sp. and Its Hepatoprotective Effects on Acute Alcohol-Induced Liver Injury In Vivo

Schizochytrium protein hydrolysate (SPH) was prepared through stepwise enzymatic hydrolysis by alcalase and flavourzyme sequentially. The proportion of hydrophobic amino acids of SPH was 34.71%. The molecular weight (MW) of SPH was principally concentrated at 180–3000 Da (52.29%). SPH was divided into two fractions by ultrafiltration: SPH-I (MW < 3 kDa) and SPH-II (MW > 3 kDa). Besides showing lipid peroxidation inhibitory activity in vitro, SPH-I exhibited high DPPH and ABTS radicals scavenging activities with IC₅₀ of 350 μg/mL and 17.5 μg/mL, respectively. In addition, the antioxidant activity of SPH-I was estimated in vivo using the model of acute alcohol-induced liver injury in mice. For the hepatoprotective effects, oral administration of SPH-I at different concentrations (100, 300 mg/kg BW) to the mice subjected to alcohol significantly decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and hepatic malondialdehyde (MDA) level compared to the untreated mice. Besides, SPH-I could effectively restore the hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities and glutathione (GSH) level. Results suggested that SPH was rich in biopeptides that could be exploited as antioxidant molecules against oxidative stress in human body.