Laccase-catalysed functionalisation of chitosan by ferulic acid and ethyl ferulate: Evaluation of physicochemical and biofunctional properties

Grafting of syringic acid onto fucoidan: Enhanced functional properties and therapeutic potential in histamine-induced liver injury

This study explores the grafting of syringic acid onto fucoidan and assesses the resultant graft's (FS) enhanced functional properties and therapeutic potential in a histamine-induced liver injury model. Utilizing a redox system of ascorbic acid and hydrogen peroxide, the grafting process achieved a grafting rate of 290.45 mg CAE/g, confirmed through UV-Vis spectroscopy, FT-IR spectroscopy, scanning electron microscopy, and thermogravimetric analysis. In vivo investigations using histamine-sensitive mice demonstrated that FS significantly mitigated histamine-induced damage, evidenced by improvements in body weight, organ index, and colon length. FS exhibited superior efficacy in restoring liver function indices (ALT, AST, ALP, GGT), enhancing antioxidant defenses (GSH, SOD), and reducing oxidative stress markers (MDA). Anti-inflammatory effects included reduced levels of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) and modulation of apoptosis-related proteins (BCl2, BAX). Additionally, FS upregulated key antioxidant genes in the Nrf2/KEAP1 pathway and downregulated inflammatory genes in the NF-κB pathway. Restoration of colonic tight junction proteins (ZO-1, Occludin, Claudin-1) and normalization of gut microbiota composition further underscored the therapeutic potential of FS. The study highlights the significant enhancement in functional properties of fucoidan through SA grafting, presenting FS as a promising candidate for developing functional foods and nutraceuticals aimed at preventing and mitigating liver damage and related disorders.

Application of Three Types of Scaffolds in Pulp Regeneration for Permanent Mature Teeth with Periapical Lesions: A Randomized Controlled Trial

OBJECTIVE

This study aimed to evaluate pulp regeneration by comparing the application of native chitosan-based scaffolds with enzymatically modified chitosan-based scaffolds in mature teeth with apical lesions, using clinical and radiographic assessments.

METHODS

The eligibility criteria for this study were participants aged between 15-45 years, free from systemic diseases and with necrotic mature single-rooted teeth with periapical lesions. The teeth were equally and randomly allocated into three groups (1: 1: 1 allocation): Group A received treatment with a Blood Clot (BC) scaffold; Group B with a combination of Native Chitosan and Blood Clot (NCS+BC) scaffold; and Group C with Enzymatically-Modified Chitosan and Blood Clot (EMCS+BC) scaffold. Clinical procedures were performed over two appointments. During the first appointment, canals underwent standardized mechanical and chemical preparation, followed by a modified triple antibiotic paste application, then sealed with glass ionomer cement. After three weeks, the antibiotic paste was removed. Subsequently, the regenerative procedure was conducted based on the group assignment. Participants were monitored at one, three, six-, and twelve months post-treatment to evaluate the treated teeth clinically and radiographically, focusing on the status of periapical lesions and tooth sensibility through cold testing. Statistical analysis included the Kruskal-Wallis and Mann-Whitney U tests to determine significant differences in healing degrees among the three groups over time. Additionally, the Chi-square test was used to assess significant differences in tooth sensibility frequencies during the cold test across the groups.

RESULTS

Thirty teeth from twenty-four participants were included. There were no significant differences in the frequencies of healing degrees among the three studied groups (BC, NCS+BC, EMCS+BC) after one, three, and twelve months. The degree of healing after six months in the EMCS+BC group was higher than in other groups, and there were no statistically significant differences in the frequencies of healing degrees after six months between the NCS+BC group and BC group. The frequencies of tooth sensibility in the cold test among the three studied groups (BC, NCS+BC, EMCS+BC) were significantly different after six and twelve months. The tooth sensibility in the BC group was smaller than that of both the NCS+BC group and EMCS+BC group, and there were no statistically significant differences in the frequencies of tooth sensibility between the NCS+BC group and EMCS+BC group.

CONCLUSION

The application of the EMCS+BC scaffold demonstrates superior outcomes in pulp regeneration after six months, with a higher degree of healing observed compared to the NCS+BC and BC groups. There were no statistically significant differences at one month, three months, and twelve months. Additionally, tooth sensitivity was more pronounced in the EMCS+BC and NCS+BC groups. (EEJ-2024- 08-132).

A Comparison Between Three Types of Scaffolds for Pulp Regeneration: A Histological Study on Dogs

OBJECTIVES

This study aims to compare the application of three types of normal scaffolds-native chitosan, enzymatically modified chitosan, and blood clot (BC)-on pulp regeneration in the teeth of experimental dogs through histological examination, to determine the quantity and type of new tissues formed within the root canal.

MATERIALS AND METHODS

The research sample consisted of 32 root canals from 20 premolars of two male local experimental dogs. The sample was randomly divided into a control group, in which no intervention was performed on the teeth, and three experimental groups based on the type of scaffold used: the BC group, the native chitosan combined with BC (NCS + BC) group, and the enzymatically modified chitosan combined with BC (EMCS + BC) group. Mechanical and chemical cleaning of the canals was performed, followed by the application of the studied scaffolds within the root canals. After 3 months, the teeth were extracted and prepared for histological study, where two variables were studied: the percentage of total vital tissue (soft and hard; VT%) and the percentage of soft vital tissue only (ST%). A one-way ANOVA and Bonferroni tests were used to determine significant differences between the groups at a 95% confidence level.

RESULTS

The VT% values were significantly higher in the EMCS + BC group compared to both the NCS + BC and BC groups. The ST% values were also significantly higher in the EMCS + BC group compared to the BC group. However, no significant differences in ST% values were observed between the NCS + BC group and either the BC or EMCS + BC groups.

CONCLUSIONS

Within the limitations of this study, we conclude that the application of enzymatically modified chitosan scaffolds combined with BC yields superior results in pulp regeneration, which contributes to the formation of pulp-like tissue and cells resembling odontoblasts, as well as apex closure with tissue resembling bone tissue.

Functionalisation and behaviours of polysaccharides conjugated with phenolic compounds by oxidoreductase catalysis: A review

Polysaccharides have been extensively studied in recent decades. Their conjugation with phenolic compounds of natural origin has demonstrated high added value, not only enhancing certain inherent properties but also introducing new ones. Recently, a sustainable approach utilizing oxidoreductase enzymes (Oxredases) (laccases (Lac), tyrosinases (Tyr) and peroxidases (Per)) has been employed, and interesting progress has been made. This review aims to provide a comprehensive understanding of the various Oxredases employed and the reaction mechanisms involved in the grafting of phenolic compounds (PCs) onto polysaccharides (PSs). We provide a detailed analysis of these reaction mechanisms based on modified polymer structural analysis techniques and supported by model reactions. The impacts of different reaction parameters on the final products are thoroughly discussed. Additionally, the properties of conjugated PS-PC are extensively explored to provide an overview of their physicochemical and functional behaviours. A comparison of the PS-PC conjugates obtained via the Oxredase approach and other existing chemical- and radical-mediated approaches is also presented, emphasizing the benefits of this enzymatic pathway. Finally, a critical analysis is proposed to identify areas of improvement, aiming to further refine this environmentally friendly approach for conjugating PSs and PCs and its scalability for industrial applications.

Preparation and structural characterization of chitosan‑sodium alginate nanocapsules and their effects on the stability and antioxidant activity of blueberry anthocyanins

This study prepared a nanocapsule (NPs) from chitosan (CS) and sodium alginate (ALG) and used them to enhance the stability of blueberry anthocyanins (BA) The optimal NPs was obtained at pH value of 3.25, BA concentration of 0.5 mg/mL and mixing ratio of CS to ALG of 1:1 (W/W). Further, the formation of composite NPs was confirmed by a series of characterization methods. The CS-BA-ALG NPs appeared spherical, smooth, and evenly distributed when observed under an optical microscope and transmission Electron Microscope. The X-ray Diffractometer and Fourier Transform Infrared spectroscopy data proved that electrostatic interaction and hydrogen bonding are dominant forces to form NPs. Thermogravimetric analysis and differential scanning calorimetry results demonstrated that the CS-BA-ALG NPs system significantly improved the thermal stability of anthocyanins. In addition, it was also proved that CS-BA-ALG NPs showed high antioxidant capacity and protection capacity.

Preparation, structural characterization, and functional properties of wheat gluten amyloid fibrils-chitosan double network hydrogel as delivery carriers for ferulic acid

It has been demonstrated that ferulic acid (FA) can be effectively encapsulated using wheat gluten amyloid fibrils (AF) and chitosan (CS) in a double network hydrogel (DN) form, with cross-linking mediated by Genipin (GP). Within this system, the DN comprising gluten AF-FA and CS-FA exhibited optimal loading metrics at a formulation designated as DN8, achieving a load efficiency of 88.5 % and a load capacity of 0.78 %. Analysis through fluorescence quenching confirmed that DN8 harbored the highest quantity of FA. Fourier-transform infrared spectroscopy (FTIR) further verified a significant increase in β-sheet content post-hydrogel formation, enhancing the binding capacity for FA. Rheological assessments indicated a transition from solution to gel, delineating the phase state of the DN. Comprehensive in vitro digestion studies revealed that DN8 provided superior sustained release properties, exhibited the highest total antioxidant capacity, and displayed potent inhibitory activities against angiotensin I converting enzyme (ACE) and acetylcholinesterase (Ach-E). Additionally, the DN significantly bolstered the stability of FA against photothermal degradation. Collectively, these findings lay foundational insights for the advancement of the wheat gluten AF-based delivery system for bioactive compounds and provided a theoretical basis for the development of functional foods.

Ferulic acid-g-tamarind gum/guar gum based in situ gel-forming powders as wound dressings

The current research endeavour aimed to synthesize ferulic acid grafted tamarind gum/guar gum (FA-g-TG/GG) based powders as wound dressings, which could form in situ gels upon contact with wound exudates. In this context, variable amounts of FA were initially grafted with TG via the Steglich esterification reaction protocol and the resulting conjugates were subsequently amalgamated with GG and lyophilized to produce dry powders (F-1 - -F-3) with average particle size within 5.10-5.54 μm and average angle of repose ∼30°. These powders were structurally characterized with 1H NMR, FTIR, DSC, TGA, XRD and SEM analyses. Pristine TG, FA-g-TG and FA-g-TG/GG powders (F-2) revealed their distinct morphological structures and variable negative zeta potential values (-11.06 mV-25.50 mV). Among various formulation (F-1-F-3), F-2 demonstrated an acceptable powder-to-gel conversion time (within 20 min), suitable water vapour transmission rates (WVTR, 2564.94 ± 32.47 g/m2/day) and excellent water retention abilities and swelling profiles (4559.00 ± 41.57 %) in wound fluid. The powders were cytocompatible and conferred antioxidant activities. The powders also displayed fibroblast cell proliferation, migration and adhesion properties, implying their wound-healing potentials. Thus, the developed in situ gel-forming powders could be employed as promising dressings for wound management.

Bioactive Hydrogel Formulation Based on Ferulic Acid-Grafted Nano-Chitosan and Bacterial Nanocellulose Enriched with Selenium Nanoparticles from Kombucha Fermentation

Selenium nanoparticles (SeNPs) have specific properties that result from their biosynthesis particularities. Chitosan can prevent pathogenic biofilm development. A wide palette of bacterial nanocellulose (BNC) biological and physical-chemical properties are known. The aim of this study was to develop a hydrogel formulation (SeBNCSFa) based on ferulic acid-grafted chitosan and bacterial nanocellulose (BNC) enriched with SeNPs from Kombucha fermentation (SeNPsK), which could be used as an adjuvant for oral implant integration and other applications. The grafted chitosan and SeBNCSFa were characterized by biochemical and physical-chemical methods. The cell viability and proliferation of HGF-1 gingival fibroblasts were investigated, as well as their in vitro antioxidant activity. The inflammatory response was determined by enzyme-linked immunosorbent assay (ELISA) of the proinflammatory mediators (IL-6, TNF-α, and IL-1β) in cell culture medium. Likewise, the amount of nitric oxide released was measured by the Griess reaction. The antimicrobial activity was also investigated. The grafting degree with ferulic acid was approximately 1.780 ± 0.07% of the total chitosan monomeric units, assuming single-site grafting per monomer. Fourier-transform infrared spectroscopy evidenced a convolution of BNC and grafted chitosan spectra, and X-ray diffraction analysis highlighted an amorphous rearrangement of the diffraction patterns, suggesting multiple interactions. The hydrogel showed a high degree of cytocompatibility, and enhanced antioxidant, anti-inflammatory, and antimicrobial potentials.

Effect of tea polyphenols on chitosan packaging for food preservation: Physicochemical properties, bioactivity, and nutrition

Chitosan packaging has been widely studied for food preservation, the application of which is expanded by the incorporation of tea polyphenols. This paper reviews the influence of tea polyphenols incorporation on chitosan-based packaging from the perspectives of physicochemical properties, bioactivity used for food preservation, and nutritional value. The physicochemical properties included optical properties, mechanical properties, water solubility, moisture content, and water vapor barrier property, concluding that the addition of tea polyphenols improved the opacity, water solubility, and water vapor barrier property of chitosan packaging, and the mechanical properties and water content were decreased. The bioactivity used for food preservation, that is antioxidant and antimicrobial properties, is enhanced by tea polyphenols, improving the preservation of food like meat, fruits, and vegetables. In the future, efforts will be needed to improve the mechanical properties of composite film and adjust the formula of tea polyphenols/chitosan composite film to apply to different foods. Besides, the identification and development of high nutritional value tea polyphenol/chitosan composite film is a valuable but challenging task. This review is expected to scientifically guide the application of tea polyphenols in chitosan packaging.

Phenolic acid-chitosan derivatives: An effective strategy to cope with food preservation problems

Chitosan, a cost-effective and eco-friendly natural polymeric material, possesses excellent film-forming properties. However, it has low solubility and biological activity, which hinders its widespread applications. To overcome these limitations, researchers have developed phenolic acid-chitosan derivatives that greatly enhance the mechanical, antibacterial and antioxidant properties of chitosan, expanding its potential application, particularly in food preservation. This review aims to provide an in-depth understanding of the structure and biological activity of chitosan and phenolic acid, as well as various synthetic techniques employed in their modification. Phenolic acid-chitosan derivatives exhibit improved physicochemical properties, such as enhanced water solubility, thermal stability, rheological properties, and crystallinity, through grafting techniques. Moreover, these derivatives demonstrate significantly enhanced antibacterial and antioxidant activities. Through graft modification, phenolic acid-chitosan derivatives offer promising applications in food preservation for diverse food products, including fruits, vegetables, meat, and aquatic products. Their ability to improve the preservation and quality of these food items makes them an appealing option for the food industry. This review intends to provide a deeper understanding of phenolic acid-chitosan derivatives by delving into their synthetic technology, characterization, and application in the realm of food preservation.

Arabic gum grafted with phenolic acid as a novel functional stabilizer for improving the oxidation stability of oil-in-water emulsion

Three kinds of phenolic acids: ferulic acid (FA), caffeic acid (CA), and gallic acid (GA) with different chemical structures were individually grafted onto Arabic gum (AG) via a laccase mediated method, and their roles in stabilizing o/w emulsions were evaluated. The total phenolic content in modified AG increased from 2.7 ± 0.2 to 18.7 ± 0.2, 19.8 ± 0.6, 22.4 ± 0.8 mg/g after 4 h of laccase catalysis, respectively. FTIR spectra of modified AGs exhibited additional phenolic characteristics, revealing the successful grafting of phenolic acids to AG structure. Compared with natural AG, modified AGs showed remarkably enhanced thermal stability, as well as antioxidant capacity in an order of gallic acid > caffeic acid > ferulic acid. The incorporation of phenolic acids into AG dramatically improved its emulsification performance. Herein, gallic acid-modified AG evinced up to 17.6 % and 12.6 % increments in emulsifying activity and emulsion stability relative to natural AG, respectively. Moreover, the oxidative stability of AG emulsions was pronouncedly meliorated by the introduced phenolic acids, especially gallic acid, as manifested by the suppressed production of primary and secondary oxidation products.

Unraveling the bioactive interplay: seaweed polysaccharide, polyphenol and their gut modulation effect

Seaweed is rich in many unique bioactive compounds such as polyphenols and sulfated polysaccharides that are not found in terrestrial plant. The discovery of numerous biological activities from seaweed has made seaweed an attractive functional food source with the potential to be exploited for human health benefits. During food processing and digestion, cell wall polysaccharide and polyphenols commonly interact, and this may influence the nutritional properties of food. Interactions between cell wall polysaccharide and polyphenols in plant-based system has been extensively studied. However, similar interactions in seaweed have received little attention despite the vast disparity between the structural and chemical composition of plant and seaweed cell wall. This poses a challenge in extracting seaweed bioactive compounds with intact biological properties. This review aims to summarize the cell wall polysaccharide and polyphenols present in brown, red and green seaweed, and current knowledge on their potential interactions. Moreover, this review gives an overview of the gut modulation effect of seaweed polysaccharide and polyphenol.

Antibacterial and antioxidant properties of phenolic acid grafted chitosan and its application in food preservation: A review

Chitosan is a bio-renewable natural polymeric material. The antibacterial and antioxidant activity of chitosan can be enhanced by grafting with phenolic acids to further expand its application in food. Therefore, this paper focuses on reviewing the structure, antimicrobial and antioxidant activities and their mechanisms with phenolic acid-g-CS, evaluating its cytotoxicity, and describing its application in various food preservation. In general, different reaction mechanisms of phenolic acid-g-CS synthesis lead to different product structures. Compared to chitosan, phenolic acid-g-chitosan exhibited enhanced antibacterial and antioxidant activities. The toxicity assessment showed that phenolic acid-g-CS is not cytotoxic. Moreover, phenolic acid-g-CS has been applied to a variety of food products such as fruits, vegetables and meat with good results. Overall, this review provides a certain reference for subsequent researchers to design phenolic acid-g-CS more rationally and for the subsequent development of phenolic acid-g-CS in food preservation.

Ultrasonication significantly enhances grafting efficiency of chitosan-ferulic acid conjugate and improves its film properties under Fenton system

Ultrasonication (US)-assisted Fenton-system (US-Fenton) with different US time was developed for synthesizing chitosan (CS)-ferulic acid (FA) conjugates. The optimal US-Fenton for a suitable time was selected for preparing a film with CS-FA conjugate and its structural, functional, rheological, and physical properties were also investigated. Compared with Fenton-system, US-Fenton enhanced the grafting ratio of the conjugates, which increased firstly and then decreased as US time. The conjugate obtained by US-Fenton for 1 min (FUS1) possessed the highest grafting ratio (121.28 mg FA/g) and its grafting time was also shortened from 12 h to 1 min contrasted with Fenton grafted method. Structural characterization results showed that FA was conjugated on CS via ester and amide bonds with decreased crystallinity. Scanning electron microscopy and molecular weight analysis indicated that the degradation degree of CS-FA conjugates increased with US time. The DPPH and ABTS radical-scavenging activities of FUS1 were the closest to ascorbic acid, and it also showed the best antibacterial effect among the test conjugates. Accordingly, FUS1 was selected to obtain the film for contrasting with CS film. FUS1 film solution exhibited a decreased viscosity. In comparison to CS film, UV transmittance of FUS1 film approached zero, and its moisture, oxygen, and carbon dioxide permeabilities significantly decreased (P < 0.05). Moreover, its water solubility and tensile strength increased by 58.09% and 25.72% than those of CS film, respectively. Therefore, US-Fenton for 1 min could be a promising method for efficiently preparing active food package materials and FUS1 film possessed broad application prospects.

Preparation and Characterization of Phenolic Acid-Chitosan Derivatives as an Edible Coating for Enhanced Preservation of Saimaiti Apricots

In this study, caffeic acid (CA) and chlorogenic acid (CGA) were incorporated onto chitosan (CS) using free radical grafting initiated by a hydrogen peroxide/ascorbic acid (H₂O₂/Vc) redox system. The structural properties of the CA (CA-g-CS) and CGA (CGA-g-CS) derivatives were characterized by UV-Vis absorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and thermal stability analysis. Then, the antioxidant and antibacterial properties were evaluated, and the effect of CGA-g-CS on the postharvest quality of Saimaiti apricot was studied. It proved that phenolic acids were successfully grafted onto the CS. The grafting ratios of CA-g-CS and CGA-g-CS were 126.21 mg CAE/g and 148.94 mg CGAE/g. The antioxidation and antibacterial activities of CGA-g-CS were better than those of CA-g-CS. The MICs of CGA-g-CS against E. coli, S. aureus, and B. subtilis were 2, 1, and 2 mg/mL. The inhibitory zones of 20 mg/mL CGA-g-CS against the three bacteria were 19.16 ± 0.35, 16.33 ± 0.91, and 16.24 ± 0.05 mm. The inhibitory effects of 0.5% CGA-g-CS on the firmness, weight loss, SSC, TA, relative conductivity, and respiration rate of the apricot were superior. Our results suggest that CGA-g-CS can be potentially used as an edible coating material to preserve apricots.

Development of a Multi-Enzymatic Approach for the Modification of Biopolymers with Ferulic Acid

A series of polymers, including chitosan (CS), carboxymethylcellulose (CMC) and a chitosan-gelatin (CS-GEL) hybrid polymer, were functionalized with ferulic acid (FA) derived from the enzymatic treatment of arabinoxylan through the synergistic action of two enzymes, namely, xylanase and feruloyl esterase. Subsequently, the ferulic acid served as the substrate for laccase from Agaricus bisporus (AbL) in order to enzymatically functionalize the above-mentioned polymers. The successful grafting of the oxidized ferulic acid products onto the different polymers was confirmed through ultraviolet-visible (UV-Vis) spectroscopy, attenuated total reflectance (ATR) spectroscopy, scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) spectroscopy. Additionally, an enhancement of the antioxidant properties of the functionalized polymers was observed according to the DDPH and ABTS protocols. Finally, the modified polymers exhibited strong antimicrobial activity against bacterial populations of Escherichia coli BL21DE3 strain, suggesting their potential application in pharmaceutical, cosmeceutical and food industries.

Laccase-mediated synthesis of bioactive natural products and their analogues

Laccases are a class of multicopper oxidases that catalyse the one-electron oxidation of four equivalents of a reducing substrate, with the concomitant four-electron reduction of dioxygen to water. Typically, they catalyse many anabolic reactions, in which mostly phenolic metabolites were subjected to oxidative coupling. Alternatively, laccases catalyse the degradation or modification of biopolymers like lignin in catabolic processes. In recent years, laccases have proved valuable and green biocatalysts for synthesising compounds with therapeutic value, including antitumor, antibiotic, antimicrobial, and antioxidant agents. Further up to date applications include oxidative depolymerisation of lignin to gain new biomaterials and bioremediation processes of industrial waste. This review summarizes selected examples from the last decade's literature about the laccase-mediated synthesis of biologically active natural products and their analogues; these will include lignans and neolignans, dimeric stilbenoids, biflavonoids, biaryls and other compounds of potential interest for the pharmaceutical industry. In addition, a short section about applications of laccases in natural polymer modification has been included.

Laccase-mediated functionalization of natamycin by gallic acids for the therapeutic effect on Aspergillus fumigatus keratitis

To improve the therapeutic effect of natamycin on fungal keratitis (FK), the grafted derivatives of natamycin and gallic acid were obtained, and the effects of the grafted derivatives on Aspergillus fumigatus (A. fumigatus) keratitis were investigated. The structure of natamycin grafted with gallic acid was identified by FT-IR and UV-Vis, and the successful synthesis of Gallic-Natamycin (GA-NAT) was proved. CCK-8 and the Draize eye test showed that GA-NAT had less cytotoxicity. Then, through in vitro antibacterial experiments such as minimum inhibitory concentration (MIC), adhesion, biofilm formation, and calcium fluorescence staining and in vivo experiments such as clinical score and plate counting, the results showed that GA-NAT had similar antifungal activity to natamycin, but had a better therapeutic effect than natamycin. Myeloperoxidase assay and immunofluorescence staining also showed that GA-NAT significantly inhibited neutrophil recruitment and activity. Moreover, It was further found that GA-NAT could inhibit the mRNA and protein expressions of LOX-1, TNF-α, and IL-1β. These results indicated that GA-NAT inhibited the fungal growth, reduced the neutrophil infiltration into cornea, and down-regulated the expression of inflammatory factors in lesions, which provides a new choice for FK treatment.

Polyphenol-Polysaccharide Complex: Preparation, Characterization and Potential Utilization in Food and Health

Polysaccharides and polyphenols coexist in many plant-based food products. Polyphenol-polysaccharide interactions may affect the physicochemical, functional, and physiological properties, such as digestibility, bioavailability, and stability, of plant-based foods. In this review, the interactions (physically or covalently linked) between the selected polysaccharides and polyphenols are summarized. The preparation and structural characterization of the polyphenol-polysaccharide conjugates, their structural-interaction relationships, and the effects of the interactions on functional and physiological properties of the polyphenol and polysaccharide molecules are reviewed. Moreover, potential applications of polyphenol-polysaccharide conjugates are discussed. This review aids in a comprehensive understanding of the synthetic strategy, beneficial bioactivity, and potential application of polyphenol-polysaccharide complexes. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Preparation, characterization and biological activity of proanthocyanidin-chitosan nanoparticles

In this study, proanthocyanidin-loaded chitosan nanoparticles (PC-CS-NPs) were produced using ionotropic gelation and characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and dynamic light scattering (DLS). The synthesized nanoparticles were smaller than 300 nm and had a spherical shape, smooth topography and homogenous morphology as observed through scanning electron microscopy (SEM). In vitro release study showed that proanthocyanidins (PC) had a sustainable release from PC-CS-NPs in different buffer media. PC-CS-NPs had higher or comparable potency in scavenging DPPH and ABTS free radicals as compared to native drugs. Furthermore, PC-CS-NPs also inhibited the growth of four bacteria species, whose degree of inhibition depended on the bacterial strain. The results of SEM confirmed the changes in the microstructure of bacteria. Our findings support the use of chitosan nanoparticles to encapsulate PC and improve its bioactivity in food products.

Characterization of Epigallocatechin-Gallate-Grafted Chitosan Nanoparticles and Evaluation of Their Antibacterial and Antioxidant Potential

Nanoparticles based on chitosan modified with epigallocatechin gallate (EGCG) were synthetized by nanoprecipitation (EGCG-g-chitosan-P). Chitosan was modified by free-radical-induced grafting, which was verified by Fourier transform infrared (FTIR). Furthermore, the morphology, particle size, polydispersity index, and zeta potential of the nanoparticles were investigated. The grafting degree of EGCG, reactive oxygen species (ROS) production, antibacterial and antioxidant activities of EGCG-g-chitosan-P were evaluated and compared with those of pure EGCG and chitosan nanoparticles (Chitosan-P). FTIR results confirmed the modification of the chitosan with EGCG. The EGCG-g-chitosan-P showed spherical shapes and smoother surfaces than those of Chitosan-P. EGCG content of the grafted chitosan nanoparticles was 330 μg/g. Minimal inhibitory concentration (MIC) of EGCG-g-chitosan-P (15.6 μg/mL) was lower than Chitosan-P (31.2 μg/mL) and EGCG (500 μg/mL) against Pseudomonas fluorescens (p < 0.05). Additionally, EGCG-g-chitosan-P and Chitosan-P presented higher Staphylococcus aureus growth inhibition (100%) than EGCG at the lowest concentration tested. The nanoparticles produced an increase of ROS (p < 0.05) in both bacterial species assayed. Furthermore, EGCG-g-chitosan-P exhibited higher antioxidant activity than that of Chitosan-P (p < 0.05) in 2,2'-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and ferric-reducing antioxidant power assays. Based on the above results, EGCG-g-chitosan-P shows the potential for food packaging and biomedical applications.

Catechin-grafted arabinoxylan conjugate: Preparation, structural characterization and property investigation

In this study, a high molecular weight arabinoxylan (AX, Mw: 694 kDa) from wheat bran was alkaline extracted and covalently linked with Catechin (CA) by free radical catalytic reaction. Comparing to AX, arabinoxylan-catechin (AX-CA) conjugates demonstrated an extra UV-vis absorption peak at 274 nm, a new FT-IR absorption band at 1516 cm^-1 and new proton signals at 6.5-7.5 ppm, which all confirmed the covalently linked structure. Grafting CA onto AX not only decreased the molecular weight, thermal stability and apparent viscosity of AX, but also enhanced its inhibition effects on starch digestibility in vitro. The in vitro fermentation test with pig feces showed that the degradation & utilization rate of AX, the total short-chain fatty acid (SCFA) and acetic acid levels produced all were significantly delayed after grafting. This study provided a novel approach to synthesize AX-CA conjugates that could be a novel dietary fiber of enhanced functional/bioactive properties using in the fields of functional foods and medicine.

Advances in laccase-triggered anabolism for biotechnology applications

This is the first comprehensive overview of laccase-triggered anabolism from fundamental theory to biotechnology applications. Laccase is a typical biological oxidordeuctase that induces the one-electronic transfer of diverse substrates for engendering four phenoxy radicals with concomitant reduction of O₂ into 2H₂O. In vivo, laccase can participate in anabolic processes to create multifarious functional biopolymers such as fungal pigments, plant lignins, and insect cuticles, using mono/polyphenols and their derivatives as enzymatic substrates, and is thus conducive to biological tissue morphogenesis and global carbon storage. Exhilaratingly, fungal laccase has high redox potential (E° = 500-800 mV) and thermodynamic efficiency, making it a remarkable candidate for utilization as a versatile catalyst in the green and circular economy. This review elaborates the anabolic mechanisms of laccase in initiating the polymerization of natural phenolic compounds and their derivatives in vivo via radical-based self/cross-coupling. Information is also presented on laccase immobilization engineering that expands the practical application ranges of laccase in biotechnology by improving the enzymatic catalytic activity, stability, and reuse rate. Particularly, advances in biotechnology applications in vitro through fungal laccase-triggered macromolecular biosynthesis may provide a key research direction beneficial to the rational design of green chemistry.

Discovery of two novel laccase-like multicopper oxidases from Pleurotus citrinopileatus and their application in phenolic oligomer synthesis

BACKGROUND

Laccases and laccase-like multicopper oxidases (LMCOs) oxidize a vast array of phenolic compounds and amines, releasing water as a byproduct. Their low substrate specificity is responsible for their tremendous biotechnological interest, since they have been used for numerous applications. However, the laccases characterized so far correspond to only a small fraction of the laccase genes identified in fungal genomes. Therefore, the knowledge regarding the biochemistry and physiological role of minor laccase-like isoforms is still limited.

RESULTS

In the present work, we describe the isolation, purification and characterization of two novel LMCOs, PcLac1 and PcLac2, from Pleurotus citrinopileatus. Both LMCOs were purified with ion-exchange chromatographic methods. PcLac2 was found to oxidize a broader substrate range than PcLac1, but both LMCOs showed similar formal potentials, lower than those reported previously for laccases from white-rot fungi. Proteomic analysis of both proteins revealed their similarity with other well-characterized laccases from Pleurotus strains. Both LMCOs were applied to the oxidation of ferulic and sinapic acid, yielding oligomers with possible antioxidant activity.

CONCLUSIONS

Overall, the findings of the present work can offer new insights regarding the biochemistry and variability of low-redox potential laccases of fungal origin. Low-redox potential biocatalysts could offer higher substrate selectivity than their high-redox counterparts, and thus, they could be of applied value in the field of biocatalysis.

Sustainable-green synthesis of silver nanoparticles using safflower (Carthamus tinctorius L.) waste extract and its antibacterial activity

Silver nanoparticles have high potential for application in food industry, as they have the ability to inhibit a wide range of bacteria of pathogenic and spoilage origin. They can be obtained from different methods classified in physical and chemical and which are aggressive with the environment since they produce toxic waste. Nowadays, environmentally friendly methods such as green synthesis can be used, through the use of agri-food waste. The use of these wastes is a more sustainable method, because it reduces the environmental pollution, at the same time that silver nanoparticles are obtained. The aim of the present study is the green synthesis of silver nanoparticles using safflower (Carthamus tinctorius L.) aqueous extract from waste and its antibacterial activity on Staphylococcus aureus (Gram positive) and Pseudomonas fluorescens (Gram negative). The analyses by TEM showed that the as-synthesized silver nanoparticles were uniform and spherical particles with an average diameter of 8.67 ± 4.7 nm and confirmed by SEM. The electron diffraction and TEM analyses showed the characteristic crystallinity of silver nanoparticles. FTIR spectroscopy confirmed that various functional groups were responsible for reducing and stabilizing during the biosynthesis process. Nanoparticles inhibited the growth of both types of bacteria from the lowest concentration evaluated (0.9 μg/mL). We conclude that silver nanoparticles synthesized in the present study have potential application as antibacterial agents in food and medicine industry.

In silico, in vitro, and in vivo investigation of antioxidant potential and toxicity of ethyl ferulate

By submitting this manuscript, each author certifies that they have made a direct and substantial contribution to the work reported in the manuscript. In this manuscript the conception, design, investigation, acquisition of data and analysis, interpretation of data and writing of the article were conducted by author Camila Bomfim de Sá under the guidance of professors Margareth de Fátima Formiga Melo Diniz, Hilzeth de Luna Freire Pessôa and Caliandra Maria Bezerra Luna Lima, who also approved the final version of the manuscript. Professor Damião Pergentino de Sousa and his student Mayara Castro de Morais performed the production, synthesis and chemical characterization of ethyl ferulate (EF). Professor Abrahão Alves de Oliveira Filho assessed the in silico tests. PhD student Andressa Brito Lira participated in the critical review of the text for important intellectual content and assisted in the in vitro antioxidant activity and cytotoxicity tests. Kardilandia Mendes de Oliveira participated in acute oral toxicity tests evaluating the biochemical parameters. Students, Tafaela Dias and Cinthia Rodrigues Melo also assisted in the acute oral toxicity testing and preparing of slides for histopathological analysis. Pathologist Alexandre Rolim da Paz analyzed the histopathology results. EF, a phenolic compound of the large class of phenylpropanoids, is derived from ferulic acid and is produced both naturally and synthetically. Its principal pharmacological activities are: anti-inflammatory and antioxidant activity. This study aimed to investigate the in silico, in vitro and in vivo toxicity and antioxidant activity of EF. The in silico prediction showed more than 20 biological activities as well as good absorption at the biological membranes and no theoretical toxicity. However, EF presented high environmental toxicity. EF presented low hemolytic potential and exerted protective activity for the erythrocyte membrane for only blood type O. EF presented antioxidant activity against H₂O₂ at all concentrations and all blood types, but no effect against phenylhydrazine, being unable to prevent its oxidative effects. In the acute nonclinical toxicological trial, the treated animals presented behavioral changes (e.g., sedation). Feed intake was higher for the 2000 mg/kg group, but with no significant difference in weight change. The biochemical parameters presented no differences between treated and control animals, and the organs remained intact with no change. Thus, EF presents a low toxic profile and this study provides important information about the toxicity of this compound, suggesting future safe use.

Conjugation of ferulic acid onto pectin affected the physicochemical, functional and antioxidant properties

BACKGROUND

Pectin, as a functional ingredient, is best known as a gelling and thickening agent, stabilizer, and fat substitute in processed foods. The synthesis of pectin graft copolymers is considered one of the most fascinating ways to improve its physicochemical and functional properties. In this study, therefore, water-soluble pectin or ultrasound-treated pectins (UP30 and UP60) grafted with ferulic acid (FA) conjugates, pectin-g-FA, UP30-g-FA and UP60-g-FA, were synthesized via a free radical-mediated grafting procedure, and their physicochemical, structural, and functional characteristics were investigated. Moreover, 2,2-diphenyl-1-picryl-hydrazyl (DPPH)-radical scavenging activity, Trolox equivalent antioxidant capacity (TEAC) assay and ferric-reducing ability of plasma (FRAP) assay were used to evaluate their antioxidant activities in vitro.

RESULTS

Results showed that FA was covalently grafted onto pectin or ultrasound-treated pectins, and the grafting ratios of pectin-g-FA, UP30-g-FA and UP60-g-FA were 65.43 ± 1.30, 82.55 ± 1.71 and 75.82 ± 0.89 mg FA/g, respectively. Although the molecular weights, apparent viscosities, and thermal stabilities of the three FA-grafted pectin conjugates decreased and their surface morphologies were different from those of native pectin and ultrasound-treated pectins, they possessed prominent DPPH-radical scavenging ability [half maximal inhibitory concentration (IC₅₀ ) of 0.32 to 0.89 mg mL^-1 ) and antioxidant capacity (TEAC of 100.02 to 153.42 μmol Trolox/g sample; FRAP: 166.41 to 270.27 μmol FeSO₄ /g sample). Their antioxidant potentials were positively correlated with the grafting ratio.

CONCLUSION

This study provided a promising strategy for the functionalization of pectin, and the prepared FA-grafted pectin conjugates could be explored as functional ingredients that showed potential for applications in food and agriculture systems. © 2020 Society of Chemical Industry.

Role of Antioxidant Molecules and Polymers in Prevention of Bacterial Growth and Biofilm Formation

Background:

Antioxidants are multifaceted molecules playing a crucial role in several cellular functions. There is by now a well-established knowledge about their involvement in numerous processes associated with aging, including vascular damage, neurodegenerative diseases and cancer. An emerging area of application has been lately identified for these compounds in relation to the recent findings indicating their ability to affect biofilm formation by some microbial pathogens, including Staphylococcus aureus, Streptococcus mutans, and Pseudomonas aeruginosa.

Methods:

A structured search of bibliographic databases for peer-reviewed research literature was performed using a focused review question. The quality of retrieved papers was appraised using standard tools.

Results:

One hundred sixty-five papers extracted from pubmed database and published in the last fifteen years were included in this review focused on the assessment of the antimicrobial and antibiofilm activity of antioxidant compounds, including vitamins, flavonoids, non-flavonoid polyphenols, and antioxidant polymers. Mechanisms of action of some important antioxidant compounds, especially for vitamin C and phenolic acids, were identified.

Conclusion:

The findings of this review confirm the potential benefits of the use of natural antioxidants as antimicrobial/antibiofilm compounds. Generally, gram-positive bacteria were found to be more sensitive to antioxidants than gram-negatives. Antioxidant polymeric systems have also been developed mainly derived from functionalization of polysaccharides with antioxidant molecules. The application of such systems in clinics may permit to overcome some issues related to the systemic delivery of antioxidants, such as poor absorption, loss of bioactivity, and limited half-life. However, investigations focused on the study of antibiofilm activity of antioxidant polymers are still very limited in number and therefore they are strongly encouraged in order to lay the foundations for application of antioxidant polymers in treatment of biofilm-based infections.

Synthesis and characterization of L-tyrosine-conjugated quaternary ammonium salt chitosan and their cytocompatibility as a potential tissue engineering scaffold

A novel amino acid-modified biomacromolecule was designed and synthesized as the quaternary ammonium salt chitosan grafted-tyrosine (CA-g-Tyr) suitable for biomedical applications. L-tyrosine was grafted onto the quaternary ammonium salt chitosan (CA) by N-(3-dimethylaminopropy)-N-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The chemical structure of CA-g-Tyr was confirmed by Fourier transform infrared (FTIR) spectroscopy and ¹³C-NMR. The change in the crystalline structure after the graft was characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The surface wettability and moisturizing performance of the CA-g-Tyr were also characterized. The CA-g-Tyr film possessed good hydrophilicity, and the mechanical tensile experiments showed that the introduction of tyrosine gave CA mechanical properties more suitable for blood vessel. Cell experiments showed that the endothelial cells can adhere and proliferate better on the surface of a CA-g-Tyr film than CA. The results confirm the favorable properties and biocompatibility of CA-g-Tyr with potential applications as scaffolds for tissue engineering.

Preparation of Gallic Acid-Grafted Chitosan Using Recombinant Bacterial Laccase and Its Application in Chilled Meat Preservation

To improve the antibacterial and antioxidant properties of chitosan (CS), CS grafted with gallic acid (GA) using recombinant bacterial laccase from Bacillus vallismortis fmb-103 (fmb-rL103) as a catalyst. The structures of grafted chitosans were identified using Fourier transform infrared spectroscopy (FT-IR) and UV visible spectrum (UV–Vis spectroscopy). After gallic acid grafting, the antibacterial properties of chitosans against Pseudomonas, Acinetobacter, Brochothrix thermosphacta, Escherichia coli, Staphylococcus aureus, Salmonella, and Listeria monocytogenes were significantly improved. Meanwhile, 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging results showed that the antioxidant properties of grafted CS increased as well. The preservative effects of the grafted chitosan on chilled meat were then investigated. For this purpose, the quality indexes of the chilled meat during the storage were monitored, including total bacterial count, total basic volatile nitrogen (TVB-N) content, pH value, color and thiobarbituric acid reactive substances (TBARS) and so on. The results showed that coating with the grafted chitosan retarded the growth of spoilage bacteria, and decreased TVB-N and TBARS values of meat. The shelf life of chilled meat coated by CS grafted with GA (GA-g-CS) also extended from 6 days to 18 days at 4°C. These results provided a theoretical basis for the future application of the GA-g-CS in the preservation of chilled meat.

Highlights:(1)

The temperature and pH-stable bacterial laccase was used to synthesize gallic acid grafted chitosan.

(2)

Antioxidant and antibacterial properties of chitosan were improved through grafting gallic acid.

(3)

Storage properties of chilled meat were improved by coating with gallic acid grafted chitosan.

Synthesis of chitin-glucan-aldehyde-quercetin conjugate and evaluation of anticancer and antioxidant activities

In the present study, we have synthesized chitin-glucan-aldehyde-quercetin (chi-glu-ald-que) conjugate via condensation reaction. Synthesis of chitin-glucan-aldehyde (chi-glu-ald) complex was facilitated by the oxidation of chitin-glucan (chi-glu) complex. Formation of conjugate was confirmed by Proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier-transform infrared spectroscopy (FT-IR). Morphological studies showed that after grafting of quercetin, several changes on surface were depicted and a more crystalline nature was observed. The chi-glu-ald-que conjugate displayed strong antioxidant activity. It showed 69% of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical, DPPH* scavenging activity at 1 mg/mL and 72% of 2, 2-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation, ABTS*⁺ scavenging activity at 1 mg/mL concentration, which are much higher than that of chi-glu complex. The anticancer activity of chi-glu-ald-que conjugate was performed in Macrophage cancer cell lines (J774) and biocompatibility was performed in Peripheral blood mononuclear cells (PBMCs). The chi-glu-ald-que conjugate showed excellent cytotoxicity against J774 cell lines but no cytotoxicity towards PBMCs.

Preparation of ferulic acid-grafted chitosan using recombinant bacterial laccase and its application in mango preservation

To improve the antioxidant and antibacterial properties of chitosan, recombinant bacterial laccase from Bacillus vallismortis fmb-103 (fmb-rL103) was used to catalyze ferulic acid grafting. The grafted chitosan was characterized using UV-vis and FT-IR techniques. DPPH free radical scavenging results indicated that the antioxidant properties of the grafted chitosan (FA-g-CS) were significantly improved. Meanwhile, the antibacterial properties against E. coli, S. aureus, B. subtilis, and M. guilliermondii were also improved. Furthermore, FA-g-CS was applied to mango preservation as a coating, which improved the sensory qualities of mango Mangifera indica L. The disease incidence of mangoes coated with FA-grafted medium and high molecular weight chitosan were 0 and 5%, respectively. The respiratory peak was delayed more than 4 days, and the titratable acidity and ascorbic acid concentration were all enhanced. POD and CAT activities in FA-g-CS coated mangoes were higher than those coated with chitosan samples with a lower H2O2 concentration.

Laccase-mediated functionalization of chitosan with 4-hexyloxyphenol enhances antioxidant and hydrophobic properties of copolymer

An effective method to functionalize chitosan with 4-hexyloxyphenol (HP) under homogeneous reaction conditions was developed using laccase as the catalyst. The resulting copolymer was characterized for chemical structure, grafted-HP content, surface morphology, thermal stability, antioxidant capacity, hydrophobic properties and tensile strength. Solid-state ¹³C NMR spectrum confirmed the incorporation of HP onto chitosan. X-ray diffraction (XRD) showed a decrease in the degree of crystallinity for laccase/HP treated chitosan compared to pure chitosan. The grafted-HP content in laccase/HP-treated chitosan first increased and then declined with increase of the initial HP/chitosan ratio. A heterogeneous surface with spherical particles on the laccase/HP treated chitosan was observed by environmental scanning electron microscopy (ESEM) and scanning probe microscopy (SPM). The laccase/HP treatment of chitosan improved the thermal stability of copolymer. More significantly, the HP functionalized chitosan showed greatly improved ABTS⁺ and DPPH radicals scavenging capacity, compared with pure chitosan. The hydrophobicity property of the HP functionalized chitosan also significantly increased although its tensile strength decreased. This new type of composite with double functionalities (i.e., antioxidant and hydrophobic) could potentially be used as food packaging materials or coating agents.

Laccase catalysis for the synthesis of bioactive compounds

The demand for compounds of therapeutic value is increasing mainly because of new applications of bioactive compounds in medicine, pharmaceutical, agricultural, and food industries. This has necessitated the search for cost-effective methods for producing bioactive compounds and therefore the intensification of the search for enzymatic approaches in organic synthesis. Laccase is one of the enzymes that have shown encouraging potential as biocatalysts in the synthesis of bioactive compounds. Laccases are multicopper oxidases with a diverse range of catalytic activities revolving around synthesis and degradative reactions. They have attracted much attention as potential industrial catalysts in organic synthesis mainly because they are essentially green catalysts with a diverse substrate range. Their reaction only requires molecular oxygen and releases water as the only by-product. Laccase catalysis involves the abstraction of a single electron from their substrates to produce reactive radicals. The free radicals subsequently undergo homo- and hetero-coupling to form dimeric, oligomeric, polymeric, or cross-coupling products which have practical implications in organic synthesis. Consequently, there is a growing body of research focused on the synthetic applications of laccases such as organic synthesis, hair and textile dyeing, polymer synthesis, and grafting processes. This paper reviews the major advances in laccase-mediated synthesis of bioactive compounds, the mechanisms of enzymatic coupling, structure-activity relationships of synthesized compounds, and the challenges that might guide future research directions.