Antimicrobial and antioxidant effects of a hydroxypyridinone derivative containing an oxime ether moiety and its application in shrimp preservation

Eco-friendly one-pot preparation of starch smart labels based on natural deep eutectic solvents self-assembly system for monitoring the shrimp freshness

Recently, smart labels for monitoring food freshness provided a powerful strategy to reduce food waste and foodborne diseases. Excellent performance, non-toxicity, and simple process were great challenges for large-scale production of smart labels. The present study proposed a one-pot approach of green preparation for smart labels integrated with curcumin/starch nanoparticles/natural deep eutectic solvents self-assembly system. The curcumin-loaded starch nanoparticles significantly improved the mechanical properties, water resistance and UV resistance of smart labels. The sensitivity to volatile amines was improved, resulting from an increase in the dispersibility of curcumin. In addition, during the monitor of shrimp freshness, the total volatile salt-based nitrogen in shrimp reached 13.23 mg/100 g after 18 h of storage, concomitant with a significant shift in the color of smart labels from yellow to orange. These results highlight the self-assembly system could be directly exploited as readily manufacturable modules to develop a simple industrial method for smart labels.

Design, synthesis, in silico ADME, DFT, molecular dynamics simulation, anti-tyrosinase, and antioxidant activity of some of the 3-hydroxypyridin-4-one hybrids in combination with acylhydrazone derivatives

Tyrosinase is the rate-limiting enzyme in synthesizing melanin. Melanin is responsible for changing the color of fruits and vegetables and protecting against skin photo-carcinogenesis. Herein, some of the hybrids of 3-hydroxypyridine-4-one and acylhydrazones were designed and synthesized to study the anti-tyrosinase and antioxidant activities. The diphenolase activity of mushroom tyrosinase using L-DOPA assayed the inhibitory effects, and the antioxidant activity was assessed using DPPH free radical. The synthesized derivatives were confirmed using 1H-NMR, 13C-NMR, IR, and Mass spectroscopy. Among analogs, compound 5h bearing furan ring with IC50=8.94 μM was more potent than kojic acid (IC50=16.68 μM). The pharmacokinetic profile of the compounds showed that the tested compounds had suitable oral bioavailability and drug-likeness properties. The molecular docking studies showed that compound 5h was located in the tyrosinase-binding site. Also, the molecular dynamics simulation was performed on compound 5h, proving the obtained molecular docking results. At the B3LYP/6-31 + G** level of theory, the reactivity descriptors for 5 g and 5h were investigated using DFT calculations. Also, IR frequency was calculated to verify DFT results with experimental data. The electrostatic potential energy of the surface and the HOMO and LUMO molecular orbitals were also studied. It agrees with experimental results that the 5h is a soft molecule and ready for chemical reaction with other interacting molecules.Communicated by Ramaswamy H. Sarma.

Preparation of curcumin-loaded chitosan/polyvinyl alcohol intelligent active films for food packaging and freshness monitoring

To fulfill the current need for intelligent active food packaging. This study incorporated the curcumin inclusion complexes (CUR-CD) into chitosan/polyvinyl alcohol polymer to develop a new intelligent active film. The structures of films were analyzed by Fourier-transform infrared (FT-IR), scanning electron microscope (SEM), and so on. The CP-Cur150 film displays exceptional mechanical properties, water vapor barrier, and UV blocking capabilities as demonstrated by physical analysis. The CP-Cur150 film exhibited free radical scavenging rates on 2,2-diazo-di-3-ethylbenzothiazolin-6-sulfonic (ABTS) (98 %) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (87 %). Additionally, it showed inhibitory effects on Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli), reducing live colony counts by approximately 2.7 and 1.3 Log10 CFU/mL, respectively. The films were used to monitor the shrimp's freshness in real time. With the spoilage of shrimp, the film exhibited clear color fluctuations, from light yellow to red. In addition, the evaluation of the impact of films on pork pH, total volatile basic nitrogen, and total bacterial counts demonstrated that the CP-Cur150 film displayed the most significant effectiveness in preserving freshness, thereby extending the shelf life of pork.

Deep Learning Used with a Colorimetric Sensor Array to Detect Indole for Nondestructive Monitoring of Shrimp Freshness

Intelligent colorimetric freshness indicator is a low-cost way to intuitively monitor the freshness of fresh food. A colorimetric strip sensor array was prepared by p-dimethylaminocinnamaldehyde (PDL)-doped poly(vinyl alcohol) (PVA) and chitosan (Chit) for the quantitative analysis of indole, which is an indicator of shrimp freshness. As a result of indole simulation, the array strip turned from faint yellow to pink or mulberry color with the increasing indole concentration, like a progress bar. The indicator film exhibited excellent permeability, mechanical and thermal stability, and color responsiveness to indole, which was attributed to the interactions between PDL and Chit/PVA. Furthermore, the colorimetric strip sensor array provided a good relationship between the indole concentration and the color intensity within a range of 50-350 ppb. The pathogens and spoilage bacteria of shrimp possessed the ability to produce indole, which caused the color changes of the strip sensor array. In the shrimp freshness monitoring experiment, the color-changing progress of the strip sensor array was in agreement with the simulation and could distinguish the shrimp freshness levels. The image classification system based on deep learning were developed, the accuracies of four DCNN algorithms are above 90%, with VGG16 achieving the highest accuracy at 97.89%. Consequently, a "progress bar" strip sensor array has the potential to realize nondestructive, more precise, and commercially available food freshness monitoring using simple visual inspection and intelligent equipment identification.

Food-grade silica-loaded gallic acid nanocomposites: Synthesis and mechanism for enhancing water-based biological activity

As the low water solubility of gallic acid (GA), its biological activities such as water-based antioxidant effect may be greatly reduced. Therefore, GA-loaded nanocomposites (F-SiO2@GA) with high water solubility were synthesized via solvent evaporation using food-grade silica (F-SiO2) as carriers in this work. The assessment of antioxidant capacity revealed that F-SiO2@GA exhibited considerably greater free-radical scavenging ability than free GA and the physical mixture of F-SiO2 and GA. In the photooxidation experiment of food-grade gardenia yellow pigment (GYP), F-SiO2@GA showed a notable antioxidant effect on GYP solution. Additionally, in the storage experiment on chilled whiteleg shrimp (Litopenaeus vannamei) treated with F-SiO2@GA, pH, total volatile basic nitrogen (TVBN), and thiobarbituric acid reactive substance (TBARS) values were effectively inhibited. In conclusion, the internal encapsulation of GA effectively prevented the self-aggregation phenomenon, thereby facilitating the exposure of its active phenolic hydroxyl group and significantly enhancing its water-based biological activity.

The stable co-pigmented roselle anthocyanin active film extended shelf life of Penaeus vannamei better: Mechanism revealed by the TMT-labeled proteomic strategy

In order to investigate the influences of modified RAE-based film on shrimp quality, the proteomic approach was performed to elucidate preservation mechanism. Results showed that the modified RAE-based film kept better shrimp quality compared with natural RAE-based film in terms of determined biochemical parameters and estimated shelf-life. Totally, 49 differentially abundance proteins (DAPs) were identified compared with shrimp without packaging. Bioinformatics analysis demonstrated that the modified RAE-based film could maintain functional DAPs which were mainly distributed in the binding, catalytic activity, etc., and metabolic signaling pathways like melanogenesis signaling pathway were remarkably enriched. Meanwhile, there were 25 DAPs showing close relationship with quality traits, and some of them, such as myosin chains, troponin I and heat shock protein were considered as the potential biomarkers to evaluate shrimp quality deterioration. In conclusion, this study revealed the preservation mechanism of modified RAE-based active film on shrimp quality at the protein molecular level.

3D Printing of smart labels with curcumin-loaded soy protein isolate

A two-step method for preparing smart labels that can monitor food freshness through color change is presented. The conventional casting method for such labels is not cost-effective, as it uses organic solvents and requires additional cutting processes. Our method is more eco-friendly and customizable, as it uses water as the sole solvent and 3D printing as the fabrication technique. First, curcumin was encapsulated with soy protein isolate (SPI) by a pH-driven method involving hydrogen bonding and hydrophobic interactions. Subsequently, the SPI-curcumin complex was blended with gelatin to create a printable ink. The ink has suitable rheological properties for extrusion, with a yield stress of 400-600 Pa and a viscosity of 122.93-142.82 Pa·s at the optimal printing temperature. The complex modulus of the ink increases to above 2 × 103 Pa when cooled to 25 °C, indicating rapid gel formation. The application of these smart labels to minced meat demonstrated their ability to reflect its freshness by transitioning from yellow to red. Furthermore, the printability and mechanical properties of the labels can be adjusted by changing the glycerol/water ratio. This innovative approach is a promising solution for producing environmentally friendly and customizable smart labels for food freshness monitoring.

Synthesis of 3-hydroxypyridin-4-one derivatives bearing benzyl hydrazide substitutions towards anti-tyrosinase and free radical scavenging activities

Tyrosinase is a vital enzyme in the biosynthesis of melanin, which has a significant role in skin protection. Due to the importance of the tyrosinase enzyme in the cosmetics and health industries, studies to design new tyrosinase inhibitors have been expanded. In this study, the design and synthesis of 3-dihydroxypyridine-4-one derivatives containing benzo hydrazide groups with different substitutions were carried out, and their antioxidant and anti-tyrosinase activities were also evaluated. The proposed compounds showed tyrosinase inhibitory effects (IC50) in the 25.29 to 64.13 μM range. Among all compounds, 6i showed potent anti-tyrosinase activity with an IC50 = 25.29 μM. Also, the antioxidant activity of derivatives by using DPPH radical scavenging indicates an EC50 value between 0.039 and 0.389 mM. Molecular docking studies were performed to reveal the position and interactions of 6i as the most potent inhibitor within the tyrosinase active site. The results showed that 6i binds well to the proposed binding site and forms a stable complex with the target protein. Furthermore, the physicochemical profiles of the tested compounds indicated drug-like and bioavailability properties. The kinetic assay revealed that 6i acts as a competitive inhibitor. Also, for the estimation of the reactivity of the best compound (6i), the density functional theory (DFT) was performed at the B3LYP/6-31+G**.

Preparation, antioxidant and tyrosinase inhibitory activities of chitosan oligosaccharide-hydroxypyridinone conjugates

Two novel chitosan oligosaccharide (COS)-hydroxypyridone (HPO) conjugates were prepared by reacting chitosan oligosaccharide with 2-chloromethyl-5-hydroxypyridone (HPO), which was synthesized by a series of reactions starting from kojic acid. The degree of substitution of COS-HPO2 reached 1.2, with a yield of 74.9%. The structure of the two conjugates (COS-HPO1 and COS-HPO2) was identified by NMR and FT-IR analysis. The two conjugates showed significantly higher free radical (DPPH•, ABTS^+• and •OH) scavenging activity and reducing power than those of COS and HPO (p < 0.05). Both COS-HPO1 and COS-HPO2 possessed significantly stronger tyrosinase inhibitory activity than those of COS, with IC₅₀ values of 0.67 and 0.28 mg/mL for monophenolase, 0.73 and 0.30 mg/mL for diphenolase, respectively. In addition, the conjugates were found to be non-toxic to RAW264.7 macrophages and MRC-5 human lung cells. This work proposes a facile method to enhance the oxidative and tyrosinase inhibitory properties of COS.

Anti-browning and antibacterial dual functions of novel hydroxypyranone-thiosemicarbazone derivatives as shrimp preservative agents: Synthesis, bio-evaluation, mechanism, and application

To develop new shrimp preservative agents with dual functions of anti-browning and antibacterial, thirteen hydroxypyranone-thiosemicarbazone derivatives were prepared according to molecular hybridization. Thereinto, compound 7j (IC₅₀ = 1.99 ± 0.19 μM) shown the strongest anti-tyrosinase activity and was about twenty-three folds stronger than kojic acid (45.73 ± 4.03 μM). The anti-tyrosinase mechanism of 7j was illustrated through enzyme kinetic, copper ion chelating ability, fluorescence quenching, ultraviolet spectrum, AFM analysis, and molecular docking study. On the other hand, antibacterial assay and time-kill kinetics analysis confirmed that 7j also had good antibacterial activity against V. parahaemolyticus (MIC = 0.13 mM). PI uptake test, SDS-PAGE, and fluorescence spectrometry analysis proved that 7j can affect the bacterial cell membrane. Finally, the shrimp preservation and safety study indicated that 7j has dual effects of inhibiting bacterial growth and preventing enzyme browning, and can be applied to the preservation of fresh shrimp.

Design and synthesis of novel stilbene-hydroxypyridinone hybrids as tyrosinase inhibitors and their application in the anti-browning of freshly-cut apples

In order to develop the tyrosinase inhibitors with potential application in food industry, a series of stilbene-hydroxypyridinone hybrids were prepared. Among these compounds, 1h was found to possess the most potent tyrosinase inhibitory effect on both monophenolase and diphenolase activities, with IC₅₀ values of 2.72 μM and 15.86 μM, respectively. The inhibitory effect of 1h on monophenolase activity was 4.6 times that of kojic acid. An inhibition kinetic assay indicated that 1h was a mixed-type and reversible inhibitor. The copper-binding and reducing ability assays, molecular docking study, intrinsic and ANS-binding fluorescence assays indicated that copper coordination and reduction is likely to be the causative mechanism for 1h-induced inhibition on tyrosinase. The results of color measurement and browning index determination indicated that treatment with 1h retarded effectively the browning of freshly-cut apples during their storage. Meanwhile, PPO and POD activities in apple slices were found to be effectively inhibited.

Effects of microbial diversity and phospholipids on flavor profile of caviar from hybrid sturgeon (Huso dauricus × Acipenser schrencki)

Thirty-seven volatiles were identified by gas chromatography-ion mobility spectrometry in sturgeon caviar. Alkenes (37, 43), alcohols (30, 36), aldehydes (9, 10), and esters (11, 13) were detected by two-dimensional gas chromatography-time-off-flight mass spectrometry in fresh and stored caviar, respectively. Alkenes (humulene, caryophyllene, longifolene, and d-limonene), aldehydes (heptanal, hexanal, pentanal, and 3-methyl butanal), and 2-ethyl-1-hexanol were sniffed and described as providing fresh, fatty, and fishy attributes by gas chromatography-olfactometry. The fungal genera of Apiotrichum, Penicillium, Filobasidium, Gibberella, and Cladosporium and 16 bacterial genera were significantly correlated with variations in the contents of 25 aldehydes and 11 ketones. Nine strains, 20 fatty acids, and 69 differential phospholipids were isolated and profiled. Glycerophosphoethanolamine (20:2/20:4), glycerophosphoethanolamine (22:6/22:5), and glycerophosphocholine (16:0/13:0) were significantly associated with the formation of odorants and the proposed mechanism of flavor formation from phospholipids is summarized. This study represents a foundation for achieving targeted preservation and flavor control of caviar.

Anti-tyrosinase, antioxidant and antibacterial activities of gallic acid-benzylidenehydrazine hybrids and their application in preservation of fresh-cut apples and shrimps

A series of gallic acid-benzylidenehydrazine hybrids were synthesized and evaluated for their tyrosinase inhibitory activity. Thereinto, compounds 5d and 5f potently inhibited tyrosinase with IC₅₀ of 15.3 and 3.3 μM, compared to kojic acid (44.4 μM). The inhibition mechanism suggested that 5d and 5f not only chelated with Cu²⁺, but also reduced Cu²⁺ to Cu¹⁺ in the tyrosinase active site. Additionally, 5d and 5f exhibited strong DPPH scavenging and antibacterial activities against Vibrio parahaemolyticu and Staphylococcus aureus, which can be attributed to the function of gallic acid and hydrazone moiety. These compounds also exhibited capacity to preserve fresh-cut apples and shrimps. Finally, 5d and 5f exhibited low cytotoxic activity in a human cell line (HEK293). Therefore, these compounds possess anti-tyrosinase, antioxidant, and antibacterial activities, and can be used in the development of novel food preservatives.

Antibacterial activity and action mechanism of a novel chitosan oligosaccharide derivative against dominant spoilage bacteria isolated from shrimp Penaeus vannamei

With the aim of exploring the potential application of a novel chitosan oligosaccharide derivative (COS-All-Tio) in shrimp preservation, six dominant spoilage bacteria in the spoiled shrimp (Penaeus vannamei) were isolated and identified as Shewanella putrefaciens (RMS1), S. putrefaciens (S2), Pseudomonas weihenstephanensis (P1), P. gessardii (P2), Aeromonas bestiarum (A1) and Aeromonas molluscorum (A2). The antibacterial effect of COS-All-Tio against the six bacterial isolates were studied. Bacterial inhibition zone determination, and minimum inhibitory concentration and minimum bactericidal concentration assays indicated that the antibacterial activity of COS-All-Tio was greatly improved when compared to that of chitosan oligosaccharide (COS). The antibacterial mechanism investigation against S. putrefaciens (RMS1) revealed that COS-All-Tio could inhibit bacterial growth by influencing of membrane integrity. Such disturbance of membrane structure resulted in the leakage of intracellular substance of the bacteria. A strong synergistic antibacterial effect against S. putrefaciens (RMS1) was observed when COS-All-Tio was used in combination with food preservatives (e.g. ε-polylysine hydrochloride). Therefore, COS-All-Tio might have potential in shrimp preservation.

Bioevaluation and molecular docking analysis of novel phenylpropanoid derivatives as potent food preservative and anti-microbials

Novel derivatives were synthesized using natural scaffold, like phenylpropanoids C₆-C₃ backbone to reduce unfavorable browning of food due to tyrosinase and oxidative spoilage. Most of the compounds displayed mushroom tyrosinase inhibition better than kojic acid. Compound CE48 exhibited better anti-tyrosinase (IC₅₀-29.64 μM) and antioxidant (EC₅₀-12.67 μM) activity than the reference compounds, kojic acid (IC₅₀-50.30 μM) and ascorbic acid (EC₅₀-14.55 μM), respectively. Compounds SAM30, SE78, 11F, and CE48 showed better anti-B. subtilis, anti-S. aureus, and anti-A. niger activity, respectively, compared to their parents. Molecular docking studies between inhibitors and mushroom tyrosinase corroborated the experimental reports, except SAM30 (glide score - 8.117) and SE78 (glide score - 6.151). In silico absorption, distribution, metabolism, excretion/toxicity (ADME/T) and toxicological studies of these newly synthesized compounds exhibited acceptable pharmacokinetic and safety profiles, like good aqueous solubility (- 3.34 to - 7.57), low human oral absorption (e.g., SAM30, SE78, FAM34), low gut-blood barrier permeability [36.67-209.88 nm/s in Cancer coli-2 (Caco-2) cells] and [19.45-91.51 nm/s in Madin-Darby Canine Kidney (MDCK) cells], low blood-brain barrier penetration, non-mutagenicity, and non-carcinogenicity. Interestingly, the synthesized compounds also possessed multifunctional properties, like microbial growth inhibitor, free radicals scavenger, and it also prevented browning of raw fruits and vegetables by inhibiting tyrosinase enzyme.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-020-02636-0.