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In this study, we investigated the protective effects of a peptide (YGDEY, Tyr-Gly-Asp-Glu-Tyr) isolated from tilapia skin gelatin hydrolysates (TGHs), against UVB-induced photoaging in human keratinocytes (HaCaT) cells. Results showed that YGDEY significantly decreased levels of intracellular reactive oxygen species (ROS), increased antioxidant factors (Superoxide Dismutase, SOD and Glutathione, GSH) expression and maintained balance between GSH and GSSG in HaCaT cells. Comet assay shows that YGDEY can protect DNA from oxidative damage. Furthermore, it significantly inhibited MMP-1 (collagenase) and MMP-9 (gelatinase) expression and increased Type I procollagen production. In addition, the molecular docking study showed that YGDEY may form active sites with MMP-1 and MMP-9. Moreover, Western blot analysis was utilized to measure the protein levels of UVB-induced mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways. Therefore, these results suggested that YGDEY has a therapeutic effectiveness in prevention of UVB-induced cellular damage, and it is a candidate worthy of being developed as a potential natural antioxidant and food additive., (© 2019 American Society for Photobiology.)

According to a previous study, YGDEY from tilapia fish skin gelatin hydrolysates has strong free radical scavenging activity. In the present study, the protective effect of YGDEY against oxidative stress induced by ethanol in HepG2 cells was investigated. First, cells were incubated with YGDEY (10, 20, 50, and 100 μM) to assess cytotoxicity, and there was no significant change in cell viability. Next, it was established that YGDEY decreased the production of reactive oxygen species (ROS). Western blot results indicated that YGDEY increased the levels of superoxide dismutase (SOD) and glutathione (GSH) and decreased the expression of gamma-glutamyltransferase (GGT) in HepG2 cells. It was then revealed that YGDEY markedly reduced the expressions of bax and cleaved-caspase-3 (c-caspase-3); inhibited phosphorylation of Akt, IκB-α, p65, and p38; and increased the level of bcl-2. Moreover, the comet assay showed that YGDEY effectively decreased the amount of ethanol-induced DNA damage. Thus, YGDEY protected HepG2 cells from alcohol-induced injury by inhibiting oxidative stress, and this may be associated with the Akt/nuclear factor-κB (NF-κB)/mitogen-activated protein kinase (MAPK) signal transduction pathways. These results demonstrate that YGDEY from tilapia fish skin gelatin hydrolysates protects HepG2 cells from oxidative stress, making it a potential functional food ingredient.

BACKGROUND: In order to utilize tilapia skin gelatin hydrolysate protein, which is normally discarded as industrial waste in the process of fish manufacture, we study the in vivo and in vitro angiotensin‐I‐converting enzyme (ACE) inhibitory activity of the peptide Leu‐Ser‐Gly‐Tyr‐Gly‐Pro (LSGYGP). The aim was to provide a pharmacological basis of the development of minimal side effects of ACE inhibitors by comparative analysis with captopril in molecular docking. RESULTS: This peptide from protein‐rich wastes showed excellent ACE inhibitory activity (IC50 = 2.577 μmol L−1) and exhibited a mixed noncompetitive inhibitory pattern with Lineweaver–Burk plots. Furthermore, LSGYGP and captopril groups both showed significant decreases in blood pressure after 6 h and maintained good digestive stability over 4 h. Molecular bond interactions differentiate competitive captopril upon hydrogen bond interactions and Zn(II) interaction. The C‐terminal Pro generates three interactions (hydrogen bonds, hydrophilic interactions and Van der Waals interactions) in the peptide and effectively interacts with the S1 and S2 pockets of ACE. CONCLUSION: LSGYGP, with an IC50 value of 2.577 μmol L−1, has an antihypertensive effect in spontaneously hypertensive rats. Through comparison with captopril, this study revealed that LSGYGP may be a potential food‐derived ACE inhibitory peptide and could act as a functional food ingredient to prevent hypertension. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Hydrogels with good mechanical and self‐healing properties are of great importance for various applications. Poly(acrylic acid)–Fe3+/gelatin/poly(vinyl alcohol) (PAA‐Fe3+/Gelatin/PVA) triple‐network supramolecular hydrogels were synthesized by a simple one‐pot method of copolymerization, cooling and freezing/thawing. The PAA‐Fe3+/Gelatin/PVA triple‐network hydrogels exhibit superior toughness, strength and recovery capacity compared to single‐ and double‐network hydrogels. The mechanical properties of the synthesized hydrogels could be tailored by adjusting the compositions. The PAA‐Fe3+/Gelatin/PVA triple‐network hydrogel with 0.20 mmol Fe3+, 3% gelatin and 15% PVA could achieve good mechanical properties, the tensile strength and elongation at break being 239.6 kPa and 12.8 mm mm−1, respectively, and the compression strength reaching 16.7 MPa under a deformation of about 91.5%. The synthesized PAA‐Fe3+/Gelatin/PVA triple‐network hydrogels have good self‐healing properties owing to metal coordination between Fe3+ and carboxylic groups, hydrogen bonding between the gelatin chains and hydrogen bonding between the PVA chains. Healed PAA‐Fe3+(0.20)/Gelatin3%/PVA15% triple‐network hydrogels sustain a tensile strength of up to 231.4 kPa, which is around 96.6% of the tensile strength of the original samples. Therefore, the synthesized triple‐network supramolecular hydrogels would provide a new strategy for gel research and expand the potential for their application. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study, we aimed to verify the effectiveness of fermentation as a pretreatment in Nile tilapia (Oreochromis niloticus) skin gelatin production and to assess its effects on the extracted gelatin. Chemical-gelatin (CG) and fermentation-gelatin (FG) were extracted using hot water from tilapia skin after immersion in chemical reagents (sodium hydroxide and butanol) and after fermentation with Bacillus velezensis FEL-BM21, respectively. FG presented a higher recovery (27.40%), yield (49.99%), and imino acid (proline and hydroxyproline) content (177.17 ± 0.35 residues/1000 residues) than CG, but had a lower molecular weight. Fourier transform infrared and circular dichroism spectroscopy confirmed that the collagen was denatured, and scanning electron microscopy revealed that FG had a more continuous filamentous structure than CG. Furthermore, except for transmittance (66.19% at 450 nm and 86.36% at 620 nm), FG exhibited higher gel strength (492.81 g), gelling point (28.93 °C), and melting point (18.33 °C) than CG. These findings suggest that fermentation can be used to treat gelatin raw materials without negatively affecting the structure of gelatin. Moreover, fermentation has potential industrial applications as an alternative to chemical treatment. • Gelatin was extracted from chemical-treated and fermented tilapia skin. • Fermentation- and chemical-treated gelatin have similar properties. • Fermentation did not negatively affect tilapia skin gelatin microstructures. • Fermentation could be used for industrialized gelatin production pretreatment. [ABSTRACT FROM AUTHOR]

In this study, 2,3-dialdehyde starch crystal was used as a novel and low-toxicity bio-crosslinker to design composite gelatin-based films with both superior mechanical and barrier properties. The starch crystal containing aldehyde group was fabricated via periodate oxidation as an efficient cross-linker to reinforce the gelatin-based bio-composite films. X-ray photoelectron spectroscopy (XPS) and 1Hydrogen nuclear magnetic resonance (1H-NMR) revealed that di-aldehyde starch crystal (Di-SC) could react and covalently cross-link with the amine group of gelatin molecules via C=N chemical bond. The tensile strength of gelatin film containing 10% di-aldehyde starch crystal (G/Di-SC-10%) exhibited a tensile strength of 70.8 MPa, which was 967% higher than that of neat gelatin film (6.7 MPa). Additionally, the hydrophobic properties, thermal stability and surface morphology of G/Di-SC-10% were significantly enhanced, and so was its UV-barrier shield efficiency. Our results indicate that the new gelatin/di-aldehyde starch crystal bio-composite film has potential practical applications in the edible film-based packaging industry. • Dialdehyde starch crystal was used to modify gelatin-based films. • Modified film had higher tensile strength than neat film (70.8 vs 6.7 MPa). • Modified film had higher surface hydrophobicity than neat film (102° vs 87.9°). [ABSTRACT FROM AUTHOR]