Skin Hydrolysates Research Articles

Evaluation of the nutritional value of freeze-dried hydrolysates obtained from fish skin

Protein hydrolysates have a wide range of applications in the food industry. The additives obtained by enzymolysis of collagen-containing secondary fish waste (fish skin) have been freeze-dried. The following protein content is established in freeze-dried protein additives: 95.4/100 g (in pollock skin hydrolysates); 94.8 (cod skin); 92.5 g/100 g (pike-perch skin). The amino acid composition of the additives includes glycine, proline, valine, lysine, and arginine. Comparison of the amino acid composition with the reference protein demonstrates a high degree of satisfaction of the daily requirement for amino acids. The utility coefficient of the amino acid composition indicates a balance of amino acids, which determines the biological value of additives from pollock skin (88.67 %), cod (86.65 %), and pike-perch (79.68 %). Protein additives contain low-molecular peptides with biologically active properties. The assessment of the harmlessness index has been carried out using the simplest organisms: growth, reproduction and absence of death of the cells of the Tetrachymena pyriformis ciliate indicate the harmlessness and high biological value of the protein of protein supplements. The obtained food supplements are proposed to be used in the production of sports nutrition products.

Antioxidant Activity of Protein Hydrolysates from Redlip Mullet (Chelon haematocheilus) Muscle and Byproducts.

Fish muscle and byproducts represent a valuable source of bioactive compounds, with their protein hydrolysates exhibiting noteworthy antioxidant properties. This study assessed the antioxidant activity of protein hydrolysates derived from the muscle and byproducts of redlip mullet (Chelon haematocheilus), utilizing different proteases (Neutrase, Alcalase, and Protamex). Hydrolysates were prepared from various parts of the fish, including muscle (white and red meat) and byproducts (frames, head, viscera, fins, skin, and scales). The enzymatic hydrolysis resulted in the highest degree of hydrolysis, achieving 83.24 ± 1.45% for skin at 60 min and 82.14 ± 4.35% for head at 30 min, when treated with Neutrase. Frames treated with Neutrase exhibited the highest protein concentration, measured at 1873.01 ± 71.11 µg/mL at 15 min. Significantly, skin hydrolysates treated with Protamex showed the highest DPPH• scavenging activity (70.07 ± 3.99% at 120 min), while those treated with Alcalase demonstrated the highest ABTS• scavenging activity (93.47 ± 0.02% at 15 min). The highest superoxide dismutase (SOD) activity (92.01 ± 1.47%) was observed in head hydrolysates treated with Protamex after 90 min. These results suggest that C. haematocheilus protein hydrolysates possess significant antioxidant activity within a short time frame of less than 120 min.

Fractionation and refining of pectic oligosaccharides derived from onion skins through continuous feed diafiltration

In this work, a diafiltration-based process was investigated for the recovery of pectic oligosaccharides produced by subcritical water hydrolysis from onion skin waste. Four tubular ceramic membranes from 100 to 1 kDa were selected based on the molecular weight of the different galacturonic acid species present in the onion skin hydrolysate. All these membranes showed high selectivity towards pectic oligosaccharides, with low retention for free galacturonic acid, monosaccharides, organic acids, and other impurities. The 50 and 100 kDa membranes completely retained pectic oligosaccharides with a molecular weight exceeding 80 kDa, accounting for approximately 30 % of the initial pectic oligosaccharides in the hydrolysate. However, the purification rate was significantly slower using the 50 kDa membrane due to the increased cake layer resistance. Furthermore, it was examined a fractionation/purification cascade involving sequential diafiltration stages using 100, 10, and 1 kDa membranes at 25 °C, TMP = 1 bar, and a crossflow velocity of 1.5 m s−1. Approximately 87 % of the initial pectic oligosaccharides were successfully recovered and purified in the retentates, highlighting their potential for diverse applications due to their narrow molecular weight distribution, while phenolic compounds and other valuable low molecular weight molecules were recovered in the final permeate.

Potential of Tilapia Skin Hydrolysate as an Antihypertensive Nutraceutical Using In Silico

Potential of Tilapia Skin Hydrolysate as an Antihypertensive Nutraceutical Using In Silico

Characterization of Fish Skin Hydrolysates Exhibiting Dipeptidyl Peptidase IV Inhibitory Activity

Dipeptidyl peptidase IV (DPP-IV) inhibitors are antidiabetic drugs that can lower blood sugar levels. There are still few reports on the DPP-IV inhibitory activity of peptides obtained from discarded fish skin. Therefore, we prepared various enzymatic hydrolysates using the skins of six fish species and investigated their DPP-IV inhibitory effects. As a result, it was found that the DPP-IV inhibitory activity of yellowtail hydrolysate by Alcalase was higher than that of other enzymes. In addition, the IC50 after ethanol fractionation was found to be lower in yellowtail and eel skin hydrolysate. Amino acid composition analysis showed that the hydrolysate obtained from the skin of the yellowtail contained the highest amount of Gly, followed by Pro, Hyp, and Ala, indicating that it was a peptide derived from type I collagen. Fractionation with ethanol showed that the DPP-IV inhibitory components were contained in the low molecular weight fraction. The artificial digestion test observed no DPP-IV inhibitory activity or average molecular weight change. The DPP-IV inhibitory peptide obtained from fish skin has the potential to be applied as a food material to various food products.

Two novel angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) inhibiting peptides from tilapia (Oreochromis mossambicus) skin and their molecular docking mechanism.

In the study, papain was used to hydrolyze tilapia (Oreochromis mossambicus) skin to obtain a tilapia skin hydrolysate (TSH) with dual angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) inhibitory activities. The resulting TSH was sequentially fractionated by ultrafiltration, size exclusion separation chromatography, and reverse-phase high-performance liquid chromatography. Its inhibitory effects on ACE and DPP-IV were determined by commercial reagent kits. Two peptides purified from TSH were identified as Gly-Pro-Leu-Gly-Ala-Leu (GPLGAL) and Lys-Pro-Ala-Gly-Asn (KPAGN) by the ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Inhibitory concentration (IC50) of GPLGAL on ACE and DPP-IV were 117.20±1.69 and 187.10±2.75µM, respectively. IC50 of KPAGN on ACE and DPP-IV were 137.40±2.33 and 259.20±2.85µM, respectively. The molecular simulation demonstrated that the binding affinities of GPLGAL to ACE and DPP-IV proteins were -8.5 and -7.4kcal/mol, respectively, whereas those of KPAGN to ACE and DPP-IV proteins were -7.9 and -6.7kcal/mol, respectively. GPLGAL interacted with 21 amino acid residues of the ACE active site, whereas KPAGN engaged with 19 amino acid residues. Additionally, GPLGAL interacted with 10 amino acid residues of the DPP-IV active site, whereas KPAGN engaged with 13 amino acid residues. The two peptides predominantly occupied the active sites of ACE (His513, Tyr523, and Ala354) and DPP-IV (Tyr662 and Arg125) through hydrogen bonding. This leads to the deactivation of ACE and DPP-IV. PRACTICAL APPLICATION: Accelerate tilapia skin development and high-value utilization; provide foundation for preparing the peptides with dual ACE and DPP-IV inhibiting activity.

Preparation and identification of antioxidant peptides from Quasipaa spinosa skin through two-step enzymatic hydrolysis and molecular simulation

Frog skin, a by-product of Quasipaa Spinosa farming, is rich in protein and potentially a valuable raw material for obtaining antioxidant peptides. This study used papain combined with acid protease to digest frog skin in a two-step enzymatic hydrolysis method. Based on a single factor and response surface experiments, experimental conditions were optimized, and the degree of hydrolysis was 30 %. A frog skin hydrolysate (QSPH-Ⅰ-3) was obtained following ultrafiltration and gel filtration chromatography. IC50 for DPPH, ABTS, and hydroxyl radical scavenging capacities were 1.68 ± 0.05, 1.20 ± 0.14 and 1.55 ± 0.11 mg/mL, respectively. Peptide sequences (17) were analyzed and, through molecular docking, peptides with low binding energies for KEAP1 were identified, which might affect the NRF2-KEAP1 pathway. These findings suggest protein hydrolysates and antioxidant peptide derivatives might be used in functional foods.

COMPARATIVE EVALUATION AND STUDING OF SOME INDIGENOUS AND INTRODUCED RED GRAPE VARIETIES

Azerbaijan is one of the ancient wine-growing country, and it is famous by its rich assortment of local grapes. Historically, in our country well-known brand wines have been prepared from aboriginal red grape varieties. Among them, we can mention branded Kurdamir kagoru, Shamakhi kagoru, Madasa and Khindogni natural wines, etc. wines made from such autochthonous grape varieties won the favor of consumers with their unique physical-chemical and organoleptic characteristics. In line with it, in recent years, to the country introduced a number of valuable grape varieties such as Merlot, Cabernet Sauvignon, Syrah and others. It is actually relevant comparative evaluation of such varieties cultivated in local conditions, including red ones. During the ripening of the studied grape varieties, the amount of sugars ranged between 197 and 265 g/dm3, titratable acids from 4.5 to 7.7 g/dm3, and active acidity between 3.08 and 3.61. The mass concentration of sugars in the Xindogni grape variety was 197 g/dm3 on average. The varieties were in ascending order of the mass concentration of sugars: Madrasa 222 g/dm3, Cabernet-Sauvignon 226 g/dm3, Merlot 240 g/dm3, and Shirvanshahi 265 g/dm3. One of the important indicators determining the quality of raw materials is known to be the sugar-acid potential, in other words, a glucoacidometric index (GAI). In the studied varieties, the GAI varied from 3.0 to 5.7. This index was higher in the Shirvanshahi variety (5.7), medium in Madrasa (4.9) and Cabernet Sauvignon (4.8), and lower in the Xindogni (3.0) and Merlot (3.1) grape varieties. Delphinidin, cyanidin, peonidin, and malvidin anthocyanidins were found in skin hydrolysates. The amount of resveratrol in the skin, seed, and leaf was 0.75-8.25mg/kg, 0.31-5.7mg/kg, and 0.01-0.25mg, respectively, depending on varieties and years. Local grape varieties had a noticeable level of aromatic alcohol content and were not at all inferior to the famous Cabernet Sauvignon grape variety. Aromatic alcohols such as β-phenylethanol, β-phenoxyethanol, and phenylcarbinol were among the compounds of importance for Kagor-type wines. A comparison of their quantity showed that the amount of these compounds in the Madrasa grape variety was more than in the other two grape varieties.

A novel angiotensin-converting enzyme (ACE) inhibitory peptide from tilapia skin: Preparation, identification and its potential antihypertensive mechanism

To obtain food-derived peptides with high ACE inhibitory activity, tilapia skin was pretreated with steam explosion prior to enzymatic hydrolysis. The results showed that steam explosion pretreatment improved the hydrolysis efficiency and ACE inhibitory activity of fish skin hydrolysates. A novel ACE inhibitory peptide VGLFPSRSF (1009.17 Da) was obtained from steam-exploded fish skin hydrolysates. VGLFPSRSF had an IC50 value of 61.43 μM for ACE inhibitory activity, showing a non-competitive binding mode and gastrointestinal enzyme hydrolysis resistance. Molecular docking results showed that VGLFPSRSF interacted with ACE receptor protein through hydrogen bonding and hydrophobic interactions. Based on the results of network pharmacological analysis and molecular docking, VGLFPSRSF might regulate blood pressure through interaction with hypertensive targets such as AKT1, ACE, CD4, REN, and MMP9. Steam-exploded tilapia skin peptides had potential antihypertension activity and might be promising to achieve high-value utilization of fish skin by-products.

Antioxidant Activity and Potential Bioactive Peptides from Skin Protein Hydrolysate of Yellowfin Tuna (<I>Thunnus albacares</I>)

Highlight Research Immersion of tuna skin using NaHCO3 at low temperatures effectively reduces the fat content. The DH value, MW, and amino acid composition are in line with the antioxidant activity of tuna skin hydrolysate. The ABTS method showed the highest antioxidant activity in tuna skin hydrolysate. FPH of tuna skin shows functional group characteristics and amino acid composition that are similar to collagen hydrolysate products. FPH of tuna skin has the potential as a source of antioxidants, ACE inhibitors, and antifibrinolytics. Abstract The tuna fillet industry produces abundant skin by-products with high protein, which has the potential as a raw material for fish protein hydrolysate (FPH) for a source of bioactive peptides. Exploration of bioactive peptides from fish skin is generally from hydrolyzed gelatin and collagen. The study aimed to produce FPH directly from tuna skin as an antioxidant and identify potential bioactive peptides. The research began by defatting using multiple concentrations of NaHCO3 and immersion times. The defatted fish skin was produced as FPH by enzymatic hydrolysis method using different papain enzyme concentrations and hydrolysis times. The selected treatments were assessed for antioxidant activity and bioactive peptides. The results showed that the defatting process using a 0.50% NaHCO3 for 30 minutes generated the highest reducing fat content in value was 80.53%. Using papain enzyme gave a significant effect on the DH of FPH, with value was 29.72-67.64%. Therefore, FPH obtained from different concentrations for 4 hours was chosen to characterize the antioxidant activity and bioactive peptide. Hydrolysis using 5% enzyme papain showed the highest antioxidant activity of DPPH, ABTS, and reducing power with values of 0.965 mg/mL, 0.495 mg/mL, and 0.415 absorbances, respectively. FPH possesses a molecular weight of 10.15-48.50 kDa. Functional groups detected were amides A, B, I, II, and III. Glycine, proline, and arginine became amino acids dominant of FPH. Based on the diversity of biopeptide compounds, several biological function candidates were detected, namely antioxidants, ACE inhibitors, and antifibrinolytics which have the potential to be used as nutraceutical products.

In silico and in vitro assessment of yellowfin tuna skin (Thunnus albacares) hydrolysate antioxidation effect

The protein hydrolysate that contains bioactive peptides of yellowfin tuna (Thunnus albacares) skin collagen with antioxidant activity has been successfully studied by using in silico and in vitro assays. We found that using the in silico assessment, the antioxidant peptides can be found from the precursor (type I α1 and α2 collagen of yellowfin tuna). Applying papain as a protease will also provide the greatest degree of hydrolysis for antioxidative peptides. The highest peptide rank peptides sequence such as Pro-Trp-Gly (PWG), Pro-His-Gly (PHG), His-Leu (HL), Ile-Arg (IR), Ala-His (AH), Glu-Leu (EL) that predicted using papain in silico. Molecular docking analysis showed all peptides derived from yellowfin tuna have hindered the substrate to access the active site of myeloperoxidase (MPO). Interestingly, the substitution of the amino acid from His (PHG, 7.1 kcal/mol) to Trp (PWG, 8.0 kcal/mol) has increased the affinity of the peptide towards MPO. They have antioxidative activities used in silico approach to MPO enzyme. We also confirm the in vitro assays for the protein hydrolysate after proteolysis using papain. The concentration and hydrolysis time will give influence the degree of hydrolysis, and antioxidant activities (P < 0.05). In conclusion, hydrolysate protein of type I α1 and α2 collagen from yellowfin tuna produced by papain hydrolysis has the potential to be used in food, active packaging material until health applications..

Extraction, purification and characterization of collagen peptide prepared from skin hydrolysate of sturgeon fish

Abstract Collagen peptides from marine organisms have drawn great attention in food, cosmetics and medicine owing to their multiple functions including antioxidant, anticancer, cardioprotection, skin protection, and wound healing effects. Recent reports have revealed that a large amount of solid waste is discarded from fisheries that could be used for producing high value-added products. This study aims to extract and purify collagens and peptides from sturgeon fish skin, a by-product obtained during the processing of sturgeon fish. A high yield of acid-soluble collagen was obtained by using acetic acid for extraction followed by sonication, while a high yield of pepsin-soluble collagen (PSC) was shown by acetic acid and sonication followed by adding acetic acid and pepsin to the residue for extraction and then sonication. Two-stage hydrolysis with pepsin first followed by flavourzyme was necessary to produce high yield of PSC peptide. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis revealed the presence of type I collagen and the structural integrity was confirmed by Fourier transform infrared spectroscopy analysis. Flavourzyme was more effective in hydrolyzing PSC into peptides with low molecular weight (MW) than pepsin, papain, alcalase, and trypsin. Purification of PSC hydrolysate with a Sephadex G-10 column to exclude peptide with MW&amp;gt;700 Da or ultrafiltration with a dialysis membrane with MW cutoff of 500 Da produced PSC peptides with MW&amp;lt;700 Da and MW&amp;lt;728 Da accounting, respectively, accounting for 40% or 52% of all the fragments based on low resolution-matrix assisted laser desorption/ionization-mass spectrometry (LR-MALDI-MS). In conclusion, with sturgeon fish skin as raw material and flavourzyme level of 5%, the highest degree of hydrolysis and yield of PSC peptides with low MW was obtained by controlling the pH at 8, temperature at 50 °C, ratio of PSC to deionized water at 1:40 (mass concentration), hydrolysis time at 4 h, and ultrafiltration with dialyzing membrane MW cutoff of 500 Da.

Photoaging induced by long-term exposure to UV irradiation and amelioration by Skipjack tuna skin hydrolysates: Targeting inhibition of MAPK and NF-κB signaling hyperactivation

• Hydrolysates from Skipjack tuna (STH), rich of GADGSVTR, ameliorated photoaging. • STH reversed the imbalance of oxidative stress and inflammatory response. • STH restored the pathological impairment of photoaging skin. • STH targeted the hyperactivation of MAPK and NF-κB signaling pathways. Excessive and long-term exposure of skin to UV irradiation induces the photoaging and previous reports have revealed the roles of oxidative stress and inflammation response in photoaging progression, which provides the potential targets for photoaging intervention. Herein, the low molecular weight hydrolysates obtained from Skipjack tuna skin (STH) were used to evaluate the ameliorating effects on photoaging and the action mechanism was further explored. Pathologically, STH significantly recovered the barrier functions and restored the impaired architectures of photoaging skin. Biochemically, the antioxidant capacity was remarkably elevated and the inflammatory cytokines were significantly reduced in photoaging skin when STH was simultaneously administrated. Moreover, the abnormalities in epidermal hyperplasia and dermal loss were dramatically improved, along with the significant increase of procollagen type Ⅰ expression and inhibition of MMP-1 activity ( P < 0.05). Furthermore, STH mitigated the phosphorylation levels of p38, JNK, ERK, IκB and p65 in photoaging skin, which strongly indicated that STH synergistically intervened the photoaging progression in SD rats via cascading modulation on the hyperactivation of MAPK and NF-κB signaling pathways. Overall, these data prove the desirable protection of STH against photoaging process and can be used as functional ingredients in cosmeceutical foods.

Effects of Spray Drying and Freeze Drying on Physicochemical Properties, Antioxidant and ACE Inhibitory Activities of Bighead Carp (Aristichthys nobilis) Skin Hydrolysates.

The physicochemical, structural properties, antioxidant, and angiotensin I-converting enzyme (ACE) inhibitory activities of fish skin protein hydrolysate (SPH) that were freeze-dried (SPH-FD) and spray-dried (SPH-SD) were investigated. SPH-SD showed abundant volatile compounds, higher DPPH radical scavenging activity and ferrous iron chelating activity than SPH-FD, while the ABTS radical scavenging activity and ACE inhibitory activity were not influenced by the drying method. Amino acid compositions showed a higher proportion of proline and hydroxyproline residues in SPH-FD. The major molecular weights were both distributed below 1000 Da. SPH-SD had spherical structures, while SPH-FD had glass shard-like structures. The results indicated that the drying method could affect the physicochemical properties of hydrolysates, and SPH-SD showed potential prospects in developing functional fortified foods.

Ammonium Sulfate and Repeated Freeze‐Thawing Recover Oil from Emulsion Separated from Salmon Skin Hydrolysate

AbstractEmulsion separated by a disk stack centrifugal separator is the leftover from salmon skin hydrolyzed collagen production, in which oil can be recovered for further uses. Impacts of ammonium sulfate (AS) at different levels (0–10%, w/w) and freeze‐thawing with various cycles (0–7) on destabilization of emulsion separated from salmon skin (Oncorhynchus nerka) hydrolysate and quality of recovered oil are investigated. Emulsion added with AS shows larger oil droplet size (p &lt; 0.05) with lower negative charge (p&lt; 0.05). Oil yield and recovery are increased (p &lt; 0.05) with augmenting concentrations of AS and freeze–thawing cycles. Highest yield (4.01%) and recovery (87.36%) (p &lt; 0.05) are obtained for oil recovered from emulsion added with 10% AS in conjunction with freeze–thawing for three cycles. Oils recovered from emulsion added with AS (0–10%) and freeze–thawed for 0 and 3 cycles show no differences in hydrolysis, oxidation, and astaxanthin content (5.19–5.62 mg kg−1 oil). Furthermore, no marked differences in fatty acid composition and FTIR spectra are observed. Therefore, the use of 10% AS in conjunction with freeze–thawing (3 cycles) is a promising means for recovery of oil from emulsion, which can be an alternative source of nutraceutical.Practical applications: Oil–water emulsion is a by‐product separated from production of salmon skin hydrolysate with the aid of a disk stack centrifugal separator (DSCS). Retained peptides could act as emulsifier and stabilize oil droplets in emulsion. To recover oil from emulsion, the destabilization of emulsion is required. Addition of ammonium sulfate (AS) can destabilize emulsion via peptides precipitation, thus liberating the oil. Moreover, the repeated freeze–thawing in combination with AS under optimal condition is shown to enhance oil yield and recovery. Therefore, oil rich in astaxanthin and polyunsaturated fatty acid from the discarded emulsion can be recovered and further exploited.

Separation and identification of collagen peptides derived from enzymatic hydrolysate of Salmo salar skin and their anti-inflammatory activity in lipopolysaccharide (LPS)-induced RAW264.7 inflammatory model.

Inflammation is considered as a major risk for the pathogenesis of chronic diseases. Due to the adverse events caused by the long-term use of anti-inflammatory drugs, it is necessary to develop alternative and safe dietary supplements from natural products against inflammation. In this study, flavourzyme hydrolysate (for 0.5hr) presented the strongest anti-inflammatory activity, which was further separated by ultrafiltration and column chromatography, followed by LC-MS/MS identification. Peptide APD, QA, KA, and WG were identified as anti-inflammatory peptides, which significantly reduced secretion of NO, IL-6, IL-1β, and TNF-α in inflammatory macrophages. Among them, peptide QA showed the best overall anti-inflammatory effect, with the IC50 value against NO production of 849.3μM. Most of the identified anti-inflammatory peptides were stably against digestion, and they had abundant frequencies in the α (I/II) chain of Salmo salar collagen. Our findings indicated the potential of S. salar skin hydrolysates as functional food to prevent inflammation. PRACTICAL APPLICATIONS: Long-term use of anti-inflammatory drugs causes adverse events like gastrorrhagia, and it is necessary to develop alternative and safe dietary supplements from natural products against inflammation. Salmo salar skin, as a major byproduct of total fish, has not been effectively utilized during processing. In this study, novel anti-inflammatory oligopeptides with high activities were separated and identified from S. salar skin gelatin hydrolysate, which were stably against digestion, and presented a high bioavailability and abundant frequencies in collagen. Our study highlighted the added value of aquatic by-products and suggested that S. salar skin collagen hydrolysate could be used as a promising dietary supplement against inflammatory diseases.

Amino acids profile changes of silver carp (Hypophthalmichthys molitrix) skin hydrolysate during hydrolyzing by Alcalase

Amino acids profile changes of silver carp (Hypophthalmichthys molitrix) skin hydrolysate during hydrolyzing by Alcalase

Effect of Different Papain Concentrations on the Properties of Chicken Skin Protein Hydrolysates

Chicken skin is a source of animal protein hydrolysate, which has a potential as an antioxidant. This study aimed to determine the effect of different concentrations of the enzyme papain on the degree of hydrolysis, antioxidant capacity, percentage of reducing power (%RP) and amino acid composition of chicken skin protein hydrolysate. Hydrolysis was carried out using papain with various concentrations (3%, 4% and 5%, w/w protein substrate) at pH 7 and 50℃ for 6 h. The degree of hydrolysis was determined by spectrophotometry. Antioxidant capacity and %RP was determined by ferric reducing antioxidant power method and expressed in milligram of ascorbic acid equivalent per gram of sample, and amino acid composition were determined using high-performance liquid chromatography. The results showed that variations in papain concentration had a significant effect (P&lt;0.05) on the degree of hydrolysis, antioxidant capacity and %RP of chicken skin hydrolysate. The papain concentration of 4% resulted in the optimum protein hydrolysate with a degree of hydrolysis of 61.68%±0.64%, an antioxidant capacity of 8.72±0.30 mg AA/g sample and a %RP of 54.12%±1.78%. The protein hydrolysates of the treated chicken skin showed a high content of amino acids, namely, glycine, glutamate, proline, arginine and aspartate.

Hydroxyproline in animal metabolism, nutrition, and cell signaling.

trans-4-Hydroxy-L-proline is highly abundant in collagen (accounting for about one-third of body proteins in humans and other animals). This imino acid (loosely called amino acid) and its minor analogue trans-3-hydroxy-L-proline in their ratio of approximately 100:1 are formed from the post-translational hydroxylation of proteins (primarily collagen and, to a much lesser extent, non-collagen proteins). Besides their structural and physiological significance in the connective tissue, both trans-4-hydroxy-L-proline and trans-3-hydroxy-L-proline can scavenge reactive oxygen species and have both structural and physiological significancein animals. The formation of trans-4-hydroxy-L-proline residues in protein kinases BandDYRK1A, eukaryotic elongation factor 2 activity, and hypoxia-inducible transcription factor plays an important role in regulating their phosphorylation and catalytic activation as well as cell signaling in animal cells. These biochemical events contribute to the modulation of cell metabolism, growth, development, responses to nutritional and physiological changes (e.g., dietary protein intake and hypoxia), and survival. Milk, meat, skin hydrolysates, and blood, as well as whole-body collagen degradation provide a large amount of trans-4-hydroxy-L-proline. In animals, most (nearly 90%) of the collagen-derived trans-4-hydroxy-L-proline is catabolized to glycine via the trans-4-hydroxy-L-proline oxidase pathway, and trans-3-hydroxy-L-proline is degraded via the trans-3-hydroxy-L-proline dehydratase pathway to ornithine and glutamate, thereby conserving dietary and endogenously synthesized proline and arginine. Supplementing trans-4-hydroxy-L-proline or its small peptides to plant-based diets can alleviate oxidative stress, while increasing collagen synthesis and accretion in the body. New knowledge of hydroxyproline biochemistry and nutrition aids in improving the growth,health and well-being of humans and other animals.

Role of fish collagen hydrolysate in attenuating inflammation-An in vitro study.

Collagen hydrolysate, an extensively used protein obtained from different sources, has various beneficial effects on human health and diseases. The benefits of collagen hydrolysate are well known and presently varied sources for the preparation of hydrolysate are being investigated. Food as a therapy to combat inflammation is presently a much-focused field of research. The present study aims at screening the anti-inflammatory property of collagen hydrolysate from the skin of Cypselurus melanurus, Catla catla, Indian mackerel, Clarias batrachus (Cb), and Pangasius pangasius (Pp) in activated RAW 264.7 macrophage cells. The fractions, Cb (C2) and Pp (P2) with anti-inflammatory property obtained after two-step chromatographic purification contained peptides in the range of 1-3kDa molecular weight. The active fractions C2 and P2 showed a reduction in gene expression of TNF-α to 1.6- and 1-fold difference, whereas IL6 expression to 30- and 40-fold difference, respectively, in comparison to LPS treatment. The suppression of inflammatory proteins (TNF-α, IL6, NFκB, and p-IκB) by fractions C2 and P2 confirmed the anti-inflammatory activity. PRACTICAL APPLICATIONS: Collagen hydrolysate and its derived low molecular weight peptides are of great interest in the field of nutraceuticals and biomedical applications. The purified peptide fraction of fish skin hydrolysate displayed a promising anti-inflammatory property. The collagen hydrolysate of Cb and Pp can be a functional food or its purified fraction used as a nutraceutical supplementation due to their anti-inflammatory property in the cellular microenvironment.