Enzymatic cross-linking of carboxymethylpullulan grafted with ferulic acid

Study of the acetylation-induced changes in the physicochemical and functional characteristics of insoluble dietary fiber from wheat bran

BACKGROUND

Wheat bran is rich in dietary fiber (DF), particularly insoluble dietary fiber (IDF). Although the benefits for human health following the consumption of these DFs have been documented, the lower water retention capacity (WRC) and other properties still limit the applications of DF. Therefore, the current research investigated the impact of acetylation on the changes in the corresponding physicochemical and functional properties of DF.

RESULTS

The current results indicated the acetylated group restricted the alignment of the molecular chains, which led to an increased amorphous phase in the fiber structure, followed by an enhanced thermal sensitivity and a reduced crystallinity as evidenced by X-ray diffraction (XRD). Moreover, the acetylation of the IDFs enhanced the cholesterol absorption capacity, but the corresponding antioxidant capacity and cation exchange capacity were reduced, which might be due to the partial loss of the phenolic compounds onto the polysaccharides during the modification. Interestingly, a lower degree of substitution (DS) of the IDF achieved from water-acetic anhydride modification led to a higher WRC and water swelling capacity (WSC). In contrast, a higher DS from acetic anhydride modification demonstrated a greatly improved in vitro hypoglycemic performance of the IDF, including α-amylase inhibitory activity and glucose dialysis retardation index (GDRI), compared to the other samples.

CONCLUSION

This study highlights a new approach to modify the functionality of IDFs via acetylation and the design of a novel IDF with hypoglycemic activity. © 2023 Society of Chemical Industry.

Free Radical-Mediated Grafting of Natural Polysaccharides Such as Chitosan, Starch, Inulin, and Pectin with Some Polyphenols: Synthesis, Structural Characterization, Bioactivities, and Applications-A Review

Polyphenols and polysaccharides are very important natural products with special physicochemical properties and extensive biological activities. Recently, polyphenol-polysaccharide conjugates have been synthesized to overcome the limitations of polysaccharides and broaden their application range. Grafted copolymers are produced through chemical coupling, enzyme-mediated, and free radical-mediated methods, among which the free radical-induced grafting reaction is the most cost-effective, ecofriendly, safe, and plausible approach. Here, we review the grafting reactions of polysaccharides mediated by free radicals with various bioactive polyphenols, such as gallic acid (GA), ferulic acid (FA), and catechins. A detailed introduction of the methods and their mechanisms for free radical-mediated grafting is given. Structural characterization methods of the graft products, including thin-layer chromatography (TLC), ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) analysis, and X-ray diffraction (XRD) are introduced. Furthermore, the biological properties of polyphenol-polysaccharide conjugates are also presented, including antioxidant, antibacterial, antidiabetic, and neuroprotection activities, etc. Moreover, the potential applications of polyphenol-polysaccharide conjugates are described. Finally, the challenges and research prospects of graft products are summarized.

Host-guest stoichiometry affects the physicochemical properties of beta-cyclodextrin/ferulic acid inclusion complexes and films

An inclusion system of embedding ferulic acid into β-cyclodextrin (FACD) with different host-guest stoichiometries was prepared by a co-precipitation method. Then, the physicochemical properties and release kinetics of the FACD were evaluated. The results of thermal analysis, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR) proved the successful embedding of FA into the β-cyclodextrin matrix. Four mathematical models were applied to adjust the ferulic acid release profile and identify preferential kinetics. The results of physicochemical properties confirmed the successful formation of the complexes. The loading capacity (LC) and encapsulation efficiency (EE) of the inclusion complex (1 : 0.5) were 41.0 ± 3.28 mg g^-1 and 52.1 ± 2.31%, respectively, which were significantly higher than other molar ratios. The release behaviour revealed that loaded FA molecules under various host-guest stoichiometries obey different release models. While lower host-guest stoichiometry (1 : 0.5) provided desirable EE, the moderate host-guest stoichiometry (1 : 1) exhibited faster release behaviour. The FACD inclusion complex could be a promising bioactive material for food preservation.

Fabrication and biomedical applications of Arabinoxylan, Pectin, Chitosan, Soy protein, and Silk fibroin hydrogels via laccase - ferulic acid redox chemistry

The unique physiochemical properties and the porous network architecture of hydrogel seek the attention to be explored in broad range of fields. In the last decade, numerous studies on the development of enzymatically cross-linked hydrogels have been elucidated. Implementing enzyme based cross-linking for fabrication of biomaterials over other crosslinking methods harbor various advantages, especially hydrogels designed using laccase exhibits mild reaction environment, high cross-linking efficiency and less toxicity. To our knowledge this is the first report reviewing the formulation of laccase mediated cross-linking for hydrogel preparation. Here, laccase catalyzed synthesis of hydrogel using polysaccharide viz. arabinoxylan, sugar beet pectin, galactomannan, chitosan etc. and proteins namely soy protein, gelatin, silk fibroin were discussed on highlighting their mechanical properties and its possible field of application. We have summarized the role of phenolic acids in laccase mediated crosslinking particularly ferulic acid which is a component of lignocellulose, serving cell rigidity via crosslinkage. The review also discusses on various biomedical applications such as controlled protein release, tissue engineering, and wound healing. It is anticipated that this review will give a detailed information on different laccase mediated reaction strategies that can be applied for the synthesis of various new biomaterials with tailor made properties.

Microgels Based on Carboxymethylpullulan Grafted with Ferulic Acid Obtained by Enzymatic Crosslinking in Emulsion for Drug Delivery Systems

Carboxymethylpullulan (CMP) grafted with ferulic acid (FA) is crosslinked with laccase by the reverse water-in-oil emulsion technique (with sunflower oil) to obtain microgels with size from 40 to 200 µm. It is demonstrated that laccase activity and dispersion time have an impact on microgels' size. Fluorescence spectroscopy of different probes (e.g., pyrene, Nile red, and curcumin) shows the nonpolar characteristics of hydrophobic microdomains formed by the FA moieties and its dimers forming the crosslinking nodes. Encapsulation and release of curcumin or lidocaine used as drug models are studied in different buffers. Curcumin is well encapsulated but retained in microgels, while lidocaine is released at 65-70% in 2 h and 30 min in buffer simulating the gastrointestinal tract and at 75-85% in 1 h in acetate buffer pH 5.6 or phosphate-buffered saline (PBS) pH 6.9.

Construction and characterization of antioxidative ferulic acid-grafted carboxylic curdlan conjugates and their contributions on β-carotene storage stability

Grafting copolymerization of phenolic acids onto polysaccharides is an important strategy to improve their biological activities. In this study, ferulic acid (FA)-grafted carboxylic curdlan conjugates, namely, Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA, were synthesized by free radical-induced grafting. Results showed that FA was covalently grafted onto carboxylic curdlans via ester bonds. The grafting ratios of Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA were 223.03 ± 12.63, 115.63 ± 5.96, and 152.30 ± 4.57 mg FA/g, respectively, which were related with the carboxylate contents, molecular weights, and chain conformations of carboxylic curdlans. Compared with carboxylic curdlans, the FA-grafted carboxylic curdlan conjugates had lower thermal stability, molecular weight, and rheological property and looser surface morphology but had more prominent antioxidant benefits in vitro, which were proportional to their grafting ratios. Moreover, good storage stability against chemical degradation was exhibited by the β-carotene in Pickering emulsions stabilized by Cur-8-g-FA with a high grafting ratio and molecular weight.

Conjugation reaction with ferulic acid boosts the antioxidant property of arabinogalactan-protein and enhances its ability to form complex with β-lactoglobulin

Ferulic acid was chemically grafted onto the arabinogalactan protein of Aegle marmelos fruit gum using 1,1'-carbonyldiimidazole as coupling reagent. Thus, grafted polysaccharides with different degrees of substitution were prepared and then characterized by gas chromatography/mass spectrometry, size exclusion chromatography, and ultraviolet-visible, infra-red, and nuclear magnetic resonance spectroscopic investigations. Fluorescence spectroscopic investigation showed hydrophobic microdomain formation in grafted polymers. The antioxidant activities of the derivatives, as determined by the 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl radical assay, were strong and increases with increasing the degree of feruloylation. Compared to parental arabinogalactan protein (K = 2.38 × 10⁶ M^-1), these grafted polymers bind more strongly with β-lactoglobulin (K = 11.4 × 10⁶ M^-1 and 8.19 × 10⁶ M^-1). Given that gum polysaccharides are valuable component in functional foods, synthesis of antioxidative graft polymer possessing good compatibility with β-lactoglobulin may have important implication.

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.

Effects of carboxymethylation, hydroxypropylation and dual enzyme hydrolysis combination with heating on physicochemical and functional properties and antioxidant activity of coconut cake dietary fibre

The effects of carboxymethylation, hydroxypropylation and dual enzyme hydrolysis combined with heating on some physicochemical and functional properties, and antioxidant activity of coconut cake dietary fibre (CCDF) were studied. Results showed that both the hydroxypropylation and carboxymethylation could effectively improve (p < 0.05) the water retention capacity (WRC), oil retention capacity (ORC), viscosity, α-amylase inhibition activity (α-AAIR), glucose dialysis retardation index (GDRI), cation-exchange capacity, emulsifying capacity index (ECI) and bile adsorption capacity (BAC) of CCDF. Moreover, the cellulase and hemicellulase hydrolysis combination with heating significantly enhanced (p < 0.05) the soluble dietary fibre content, WRC, emulsion stability, GDRI, α-AAIR and BAC of CCDF; but caused decrease in ORC and browning of color. In addition, improvement of total phenol content, Fe²⁺ chelating ability, ABTS⁺· and O₂^-· scavenging activity were obtained in carboxymethylaticted CCDF. These effects were mainly attributed to the composition and structural modifications as evident from SEM, FT-IR and XRD analysis.

Enzymatic crosslinking to fabricate antioxidant peptide-based supramolecular hydrogel for improving cutaneous wound healing

Peptide-based supramolecular hydrogels are promising scaffold materials and have been utilized in many fields. The mechanical properties of peptide hydrogels are usually enhanced by synthetic or natural polymers to expand their application scope. In this study, antioxidant supramolecular hydrogels based on feruloyl-modified peptide and glycol chitosan were fabricated via a mild laccase-mediated crosslinking reaction. A natural polysaccharide derivative, feruloyl glycol chitosan (GC-Fer), was used to enhance the mechanical properties of peptide hydrogels. Feruloyl groups were introduced into the gel matrix via covalent bonds, which endowed the hydrogels with inherent antioxidant properties. This was beneficial for their in vivo application via scavenging harmful free radicals existing in a cutaneous wound. Further in vivo experiments demonstrated that the feruloyl-containing antioxidant hydrogel can improve the cutaneous wound healing process. The regeneration process of mature epithelium and connective tissues was accelerated in a full-thickness skin defect model.

Structural and rheological properties of pectic polysaccharide extracted from Ulmus davidiana esterified by succinic acid

The present study was carried out to investigate the physicochemical and structural properties of pectic polysaccharide extracted from Ulmus davidiana (UDP) and to determine the physicochemical, structural, and rheological properties of esterified UDP with succinic acid (ES-UDP). The results indicated that UDP had high amounts of galacturonic acids and various neutral sugars, such as galactose, rhamnose, and glucose. UDP was identified as a low methoxyl pectin, consisting of 1,4-linked α-d-GalpA (the main backbone chain), supported by the results of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, and 1D Nuclear magnetic resonance (NMR) spectroscopy. In the FT-IR and XRD, no difference was detected between UPD and ES-UDPs. However, ¹H and ¹³C NMR spectra revealed that the new ester bonds were formed between a hydroxyl group of UDP and a carboxyl group of succinic acid during esterification. In the steady shear rheological analysis, the consistency index (K) of ES-UDP was significantly higher than that of UDP and increased significantly with increasing concentration of succinic acid. In the dynamic rheological analysis, the tan δ values of all ES-UDP solutions were significantly lower than those of the UDP solution.