Preparation of curcumin-loaded pectin-nisin copolymer emulsion and evaluation of its stability.

In the paper, Nisin was grafted onto native pectin by the 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC·HCl) method. Structure characterisation showed that the carboxyl group of pectin interacted with the amino group of Nisin and formed an amide bond. The highest grafting ratio of the modified pectin was up to 24.89 %. The emulsifying property of modified pectin, significantly improved, and emulsification performance improved with increasing grafting ratio. Emulsifying activity, emulsion stability, Zeta potential, and droplet morphology data demonstrate a notable enhancement in pectin's emulsifying properties due to Nisin's introduction, with the degree of grafting showing a direct correlation with the improvement observed. Pectin-based emulsion is utilized to load curcumin, enhancing its stability and bioavailability. Research findings highlight that the incorporation of Nisin-modified pectin significantly elevates curcumin encapsulation efficiency, while decelerating its release rate. Moreover, the stability of curcumin loaded in the modified pectin under light exposure, alkaline conditions, and long-term storage is also significantly improved. Ultimately, the bioavailability of curcumin escalates from 0.368 to 0.785.

Preparation of amphoteric double network hydrogels based on low methoxy pectin: Adsorption kinetics and removal of anionic and cationic dyes.

The objective of this research was to devise a functional hydrogel was synthesized using pectin (PE), acrylic acid (AA), dimethyldiallyl ammonium chloride (DC), and polyvinyl alcohol (PVA), designed to adsorb both cationic and anionic dyes concurrently. The low methoxy pectin formed double network hydrogel through chemical and physical crosslinking with AA and PVA respectively. DC is combined into the hydrogel system through copolymerization reaction. Analysis of hydrogel's physicochemical properties was conducted using techniques such as infrared spectroscopy, texture analysis, thermogravimetry, and scanning electron microscopy. Dyes adsorption studies showed that the LP/AA/DC/PVA-2 hydrogel, prepared at the molar ratio of AA to DC of 1:2, exhibited higher adsorption efficiency for methylene blue (MB) and Congo red (CR). Kinetics and isotherms studies indicated that the adsorption behavior conformed to the pseudo-second-order kinetic model and Langmuir isotherm model. By the Langmuir isotherm fitting, the maximum adsorption capacities of MB and CR by LP/AA/DC/PVA-2 were recorded to be 222.65 mg/g and 316.46 mg/g, respectively. The adsorption mechanism is dominated by the hydrogen bonding and electrostatic interactions. Further, the adsorption and desorption experiments demonstrated that LP/AA/DC/PVA-2 hydrogel have excellent reusability.

Pectin grafted with resorcinol and 4-hexylresorcinol: Preparation, characterization and application in meat preservation.

To augment the functional attributes of pectin and expand its prospective utilization in food preservation, this research explored the enzymatic grafting of resorcinol and 4-hexylresorcinol onto pectin. Structural analysis verified the successful grafting of both resorcinol and 4-hexylresorcinol to pectin via esterification, with the 1-OH of resorcinol and 4-hexylresorcinol and the carboxyl group of pectin functioning as grafting sites. The grafting ratios of resorcinol-modified pectin (Re-Pe) and 4-hexylresorcinol-modified pectin (He-Pe) were 17.84 % and 10.98 %, respectively. This grafting modification notably enhanced the antioxidative and antibacterial properties of pectin. Specifically, DPPH clearance and the inhibition ratio in the ß-carotene bleaching assay increased from 11.38 % and 20.13 % (native pectin, Na-Pe) to 41.15 % and 36.67 % (Re-Pe), and 74.72 % and 53.40 % (He-Pe). Moreover, the inhibition zone diameter against Escherichia coli and Staphylococcus aureus rose from 10.12 and 10.08 mm (Na-Pe) to 12.36 and 11.52 mm (Re-Pe), and 16.78 and 14.87 mm (He-Pe). Additionally, the application of native and modified pectin coatings effectively impeded pork spoilage, with the modified pectins demonstrating a more potent effect. Among the two modified pectins, He-Pe exhibited the most significant enhancement in pork shelf life.

Preparation of hydrogels based on pectin with different esterification degrees and evaluation of their structure and adsorption properties.

In this study, pectin (Pe) with different esterification degrees was used as raw materials to prepared hydrogel adsorbents via free radical polymerization. The effect of Pe esterification degree on hydrogel structure and adsorption performance was studied by FTIR, SEM and XPS characterization and copper ion adsorption experiment. The results demonstrated that the carboxyl group in the hydrogels was bonded to Cu2+ through electrostatic force and coordination, which was an important factor in its adsorption capacity. The hydrogels prepared from Pe with low esterification degree had finer pores and higher carboxyl content, so the adsorption capacity on both water and Cu2+ was stronger. The preparation of hydrogels from low-ester Pe was more conducive to the adsorption of copper ions. Besides, the adsorption behavior of the hydrogels on Cu2+ was investigated through the adsorption thermodynamics and kinetics. The results indicated that the adsorption kinetics of the hydrogels was in accordance with the quasi-second-order model. The adsorption of Cu2+ by hydrogels was the result of physical and chemical adsorption, which was endothermic under natural condition, and a higher temperature will result in more favorable spontaneous adsorption.

Preparation of functionalized pectin through acylation with alkyl gallates: Experiments coupled with density functional theory.

The covalent grafting of alkyl gallates onto pectin using a lipase-catalyzed reaction in a tetrahydrofuran/aqueous medium process acylated pectin molecules with excellent antioxidant and antibacterial properties. The alkyl gallates including methyl, ethyl, and propyl gallates were enzymatically grafted onto pectin molecule, in order to study the effect of alkyl gallates on the functional modification of pectin. The grafting mechanism was analyzed by ultraviolet-visible spectrum (UV-Vis), Fourier transform infrared spectrum (FTIR), proton nuclear magnetic resonance (1HNMR), and density functional theory (DFT). Results suggested that lipase grafted 4-OH of alkyl gallate onto pectin by catalyzing esterification in organic/aqueous solution, and the grafting rate was affected by the length of alkyl chain of the gallates molecule. In vitro experiments, the acylated pectins exhibited stronger antioxidant activity in the DPPH test and ß-carotene bleaching test and were found to have obvious antimicrobial performance against Escherichia coli and Staphylococcus aureus.

Investigation of the pectin grafting with gallic acid and propyl gallate and their antioxidant activities, antibacterial activities and fresh keeping performance.

In this paper, a method for the enzymatic modification of pectin, in which gallic acid (GA) and propyl gallate (PG) were grafted onto pectin molecules in an aqueous/organic two-phase system catalyzed by lipase, was proposed. The potential reaction mechanism was explored through UV-Vis, FTIR and 1H NMR spectroscopic methods and density functional theory. Results suggested that the lipase played a dual role during the modification by catalyzing the hydrolysis of methyl ester bonds of pectin in the aqueous phase and the esterification between the 4-OH of GA and PG and the -COOH of pectin in the organic phase. Moreover, the effects of GA and PG on the antioxidant and the antibacterial activities of pectin were evaluated, and results showed that the antioxidant and the antibacterial activities of modified pectin were better than those of native pectin. The effect of modified pectin on the quality of fresh bass (Lateolabrax maculatus) was further studied. Results suggested that, compared to control group, the total viable count, histamine level, malondialdehyde content and acid value of bass fillets treated with modified pectin were significantly reduced, whereas the sensory score was significantly increased.

Investigation of a Lipase-Catalyzed Reaction between Pectin and Salicylic Acid and Its Isomers and Evaluation of the Emulsifying Properties, Antioxidant Activities, and Antibacterial Activities of the Corresponding Products.

This study presents a method for modifying pectin with phenolic acids catalyzed by lipase in a two-phase system of water/tetrahydrofuran. Salicylic acid (SA) and its isomers, including m-hydroxybenzoic acid (MHBA) and p-hydroxybenzoic acid (PHBA), were grafted onto pectin, and the products were characterized via UV-vis, Fourier transform infrared spectroscopy (FTIR), and 1H NMR analyses to explore the reaction process and mechanism between pectin and the three phenolic acids. Results indicated that lipase played a dual role in the reaction, namely, catalyzing the hydrolysis of the methyl group in the aqueous phase and esterifying the carboxyl group of pectin with the phenolic hydroxyl group of the phenolic acids in tetrahydrofuran. The grafting ratio of SA-modified pectin, MHBA-modified pectin, and PHBA-modified pectin was 1.89, 10.58, and 20.32%, respectively, and it was affected by the position of phenolic hydroxyl. Moreover, the effects of phenolic acids on the emulsifying properties, antioxidant activities, and antibacterial activities of the native and modified pectins were evaluated. In several aspects, the emulsifying properties of the modified pectins were better than those of native pectin. Moreover, the grafting of phenolic acids only slightly affected the 1,1-diphenyl-2-picryl hydrazine (DPPH) clearance of the modified pectins but substantially improved their inhibition ratio in a ß-carotene bleaching assay. Furthermore, the modified pectins exhibited better bacteriostatic activity against both Escherichia coli and Staphylococcus aureus than native pectin.

Preparation of acylated pectin with gallic acid through enzymatic method and their emulsifying properties, antioxidation activities and antibacterial activities.

In this study, native pectin (Na-Pe) was acylated with gallic acid through enzymatic method. UV-Vis, Fourier transform infrared spectroscopy and proton NMR analyses demonstrated that the phenolic hydroxyl group on gallic acid attacked the carbomethoxy of Na-Pe and replaced the methoxy group to form a new ester group under catalysis. The galloyl content of acylated pectin prepared via 24-h reaction (Ac1-Pe) was 16.8%, while that prepared via 48-h reaction (Ac2-Pe) reached 20.7%. The emulsifying properties, antioxidation activities and antibacterial activities of acylated pectin was significantly improved compared with those of Na-Pe. The emulsion activity and emulsion stability of the pectin emulsion improved from 1.08% and 56.13% (Na-Pe) to 1.57% and 88.27% (Ac1-Pe) and 1.71% and 93.3% (Ac2-Pe), respectively. The DPPH clearance of the pectin improved from 2.68% (Na-Pe) to 68.92% (Ac1-Pe) and 76.98% (Ac2-Pe) and the inhibition ratio in the ß-carotene bleaching assay of the pectin increased from 3.15% (Na-Pe) to 73.02% (Ac1-Pe) and 78.96% (Ac2-Pe). The inhibition rate of the pectin against Escherichia coli and Staphylococcus aureus also improved from 2.93% and 8.92% (Na-Pe) to 26.95% and 42.18% (Ac1-Pe) and 31.56% and 47.87% (Ac2-Pe), respectively.

Resveratrol attenuates excessive ethanol exposure induced insulin resistance in rats via improving NAD+ /NADH ratio.

SCOPE: Resveratrol has been shown to improve insulin resistance via activating the NAD+ -dependent deacetylase SIRT1, but the effects of resveratrol on ethanol-induced insulin resistance remain unclear. This study was designed to explore the potential mechanism by which resveratrol ameliorated ethanol-induced insulin resistance, focusing on its regulations on the ratio of NAD+ /NADH and SIRT1 expression. METHODS AND RESULTS: Male Sprague-Dawley rats were fed either control or ethanol liquid diets containing 0.8, 1.6 and 2.4 g/kg·bw ethanol with or without 100 mg/kg·bw resveratrol for 22 weeks. Resveratrol improved ethanol (2.4 g/kg·bw) induced reductions in insulin sensitivity, SIRT1 expression (51%, P < 0.05), NAD+ /NADH ratio (196%, P < 0.01) as well as the expression and activity of ALDH2 while decreased the augmentations in the expression and activity of ADH and CYP2E1. In primary rat hepatocytes, ethanol exposure (25 mmol/L, 24 h) similarly decreased SIRT1 expression and NAD+ /NADH ratio (33%, P < 0.05; 32%, P < 0.01), and 0.1 µmol/L resveratrol treatment reversed these decreases and inhibited the expressions of ADH and CYP2E1. CONCLUSION: Resveratrol exhibits benefits against ethanol-induced insulin resistance via improving the ratio of NAD+ /NADH to regulate SIRT1, which is associated with the modulation of ethanol metabolism enzymes.

Thermosensitive injectable hydrogel enhances the antitumor effect of embelin in mouse hepatocellular carcinoma.

Embelin, an active ingredient of traditional herbal medicine, is used to treat many diseases such as cancer. However, embelin is hydrophobic and insoluble in water, which makes it unsuitable for in vivo applications. In this study, we constructed an embelin-loaded thermosensitive injectable hydrogel system that we named Embelin/PECT(gel) based on the amphiphilic triblock copolymer of poly (ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone)-poly (ethylene glycol)-poly (ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone) (PECT). The cytotoxicity and the antitumor effects of Embelin/PECT(gel) on mouse hepatic cancers were investigated in vitro and in vivo. Results indicated that embelin was formulated in PECT hydrogel and could be continuously released from Embelin/PECT(gel) , showing a higher cytotoxicity for H22 cells in vitro compared with free embelin. The aqueous solution of Embelin/PECT(gel) transformed into gel at the injection site within seconds, which later eroded and degraded over time in vivo. A single local peritumoral injection of Embelin/PECT(gel) in liver at a low dosage of 0.5 mg per mouse exhibited a significant antitumor effect, which was comparable to the antitumor effect of the embelin solution treatment at a total dose of 6 mg per mouse in mouse hepatic cancer. Embelin/PECT(gel) , as a drug delivery system in liver, represents a novel therapeutic drug candidate for the clinical treatment of advanced hepatocellular carcinoma.