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Abstract Although ultraviolet (UV)/H2O2 treatment could effectively improve the bioactivities of polysaccharides, the relationship between free radical‐induced structural changes and the bioactivities of products remains unknown. Therefore, this work investigated the changes in the chemical characteristics and chain conformations of degraded dextrans by the UV/H2O2 system as well as their antioxidant and anti‐inflammatory activities. The apparent degradation efficiencies of dextrans under different UV/H2O2 parameters were first investigated. UV/H2O2 treatment effectively destroyed the pyranose rings and glycosidic bonds of dextrans and significantly improved their uronic acid and carboxy contents. Furthermore, conformational studies revealed that besides the rapid decrease in the molecular weight, the compact spherical conformation of dextrans was gradually depolymerized into the flexible random coil conformation. Moreover, the significant antioxidant and anti‐inflammatory activities of the degraded dextrans were mainly attributed to their more extended random coil chains, increased quantity of reducing groups, and lower molecular sizes. This study contributes to investigating the structure–activity relationship of polysaccharides prepared by free radicals‐mediated degradation.

Abstract The intestinal barrier is critical in maintaining gut homeostasis and host health. The intestinal barrier dysfunction contributes to intestinal and systemic diseases like inflammatory bowel disease, colorectal cancer, and metabolic syndromes. This review summarizes the physicochemical properties of three main kinds of brown seaweed polysaccharides (BSP), laminarin, fucoidan, and alginate, along with their absorption and metabolism in the intestine and their effects on the intestinal barrier. The physicochemical properties of BSP were closely related to their beneficial effects on intestinal health. BSP were not digested directly in the upper gastrointestinal tract but could be utilized through fermentation by the gut microbiota. BSP kept the integrity of intestinal epithelium by ameliorating intestinal oxidative stress through the nuclear factor erythroid 2‐related factor 2 signaling pathway. They also reduced tight junction dysfunction and intestinal permeability and increased the expression of mucins. Moreover, BSP regulated the composition and abundance of gut microbiota and promoted the production of beneficial metabolites such as short‐chain fatty acids. This review will help to understand the gut health‐promoting functions of the natural compounds derived from brown seaweed and offer a new perspective on intestinal disease prevention and therapy with high effectiveness and safety.

Viral diseases of potatoes are among the main problems causing deterioration in the quality of tubers and loss of yield. The growth and development of potato plants largely depend on soil moisture. Prevention strategies require comprehensive protection against pathogens and abiotic stresses, including modeling the beneficial microbiome of agroecosystems combining microorganisms and immunostimulants. Chitosan and its derivatives have great potential for use in agricultural engineering due to their ability to induce plant immune responses. The effect of chitosan conjugate with caffeic acid (ChCA) in combination with Bacillus subtilis 47 on the transcriptional activity of PR protein genes and changes in the proteome of potato plants during potato virus Y (PVY) infection and drought was studied. The mechanisms of increasing the resistance of potato plants to PVY and lack of moisture are associated with the activation of transcription of genes encoding PR proteins: the main protective protein (PR-1), chitinase (PR-3), thaumatin-like protein (PR-5), protease inhibitor (PR-6), peroxidase (PR-9), and ribonuclease (PR-10), as well as qualitative and quantitative changes in the plant proteome. The revealed activation of the expression of marker genes of systemic acquired resistance and induced systemic resistance under the influence of combined treatment with B. subtilis and chitosan conjugate indicate that, in potato plants, the formation of resistance to viral infection in drought conditions proceeds synergistically. By two-dimensional electrophoresis of S. tuberosum leaf proteins followed by MALDI-TOF analysis, 10 proteins were identified, the content and composition of which differed depending on the experiment variant. In infected plants treated with ChCA, the synthesis of proteinaceous RNase P 1 and oxygen-evolving enhancer protein 2 was enhanced in conditions of normal humidity, and 20 kDa chaperonin and TMV resistance protein N-like was enhanced in conditions of lack of moisture. The virus coat proteins were detected, which intensively accumulated in the leaves of plants infected with potato Y-virus. ChCA treatment reduced the content of these proteins in the leaves, and in plants treated with ChCA in combination with Bacillus subtilis, viral proteins were not detected at all, both in conditions of normal humidity and lack of moisture, which suggests the promising use of chitosan derivatives in combination with B. subtilis bacteria in the regulation of plant resistance.

Abstract An alginate (named P1) prepared from Sargassum fusiforme has been proven to have significant anti‐photoaging activity in our previous study. In this study, alginate lyase was used to obtain P1 hydrolysates with different molecular weights, and their structural characteristics and anti‐photoaging activity were compared. Results showed that alginate lyases could rapidly degrade the molecular weight of P1 and slightly changed its chemical composition. Fourier transform infrared spectra indicated that alginate lyase treatment did not change the main functional groups of P1. Moreover, the inhibitory effects of P1 on MMPs (MMP‐1, MMP‐3 and MMP‐9) and reactive oxygen species were also improved after hydrolyzed with alginate lyase, especially sample A‐30 (hydrolysis for 30 min). Methylation and nuclear magnetic resonance results indicated that the main chain of A‐30 was →4)‐β‐ManA‐(1→4)‐α‐GulA‐(1→4)‐β‐ManA‐(1→4)‐β‐ManA‐(1→4)‐α‐GulA‐(1→4)‐β‐ManA‐(1→3, 4)‐β‐ManA‐(1→, with the end group of α‐Fucp‐(1→ attached to the O‐3 position of →3, 4)‐β‐ManA‐(1→ on the side chain. It indicated that alginate lyase did not change the backbone of P1 but decreased the molecular or degree of polymerization at 30 min of hydrolysis. This is the first report on the anti‐photoaging activity of alginate hydrolysates. The results will provide effective theoretical support for improving the utilization and promoting the application of S. fusiforme.

The main purpose of this study was to analyze the structural properties and anti-inflammatory activity of the purified fractions derived from UV/H2O2-degraded polysaccharides from Sargassum fusiforme. Results indicated that twofractions with different monosaccharide compositions and morphological characteristics, PT-0.25 (yield 39.5%) and PT-0.5 (yield 23.9%), were obtained. The average molecular weights of PT-0.25 and PT-0.5 were 14.52 kDa and 22.89 kDa, respectively. In addition, PT-0.5 exhibited better anti-inflammatory activity with a clear dose dependence. The mechanism was associated with the inhibition of LPS-activated Toll-like receptor 4-mediated inflammatory pathways in RAW264.7 cells. The results showed that PT-0.5 was a complex polysaccharide mainly composed of 4-Fucp, t-Manp, 6-Galp, t-Fucp, and 3,4-GlcAp. These results would provide theoretical support for studying the structural properties and biological activities of UV/H2O2-degraded polysaccharides.

Abstract The search for novel efficient antibacterial agents is attracting a great attention due to the unregulated use of common antibiotics and development of multidrug‐resistant bacteria strains. This paper proposes an eco‐friendly approach to obtain stable chitosan‐capped silver nanoparticles with controlled physicochemical and biological properties using reducing and stabilizing capacity of chitosan. The study of the influence of chitosan characteristics on the kinetic of Ag+ reduction showed that an increase in polysaccharide molecular weight led to a decrease in their reducing ability. The synthesized silver nanoparticles were characterized by UV and FTIR spectroscopy, TEM, XRD, DLS. The relationships between physicochemical characteristics of the formed silver nanoparticles and the type of used chitosan, as well as synthesis temperature, were determined. It has been demonstrated that spherically‐shaped (13–27 nm) and positively‐charged (zeta‐potential 26.1–29.5 mV) silver nanoparticles with a single symmetric SPR band at 408–418 nm are stable during 6 months in a colloidal form, and can be produced with the assistance of low‐molecular weight chitosan (20–30 kDa) at 95°C. The synthesized silver nanoparticles enhanced the antibacterial activity of kanamycin and ampicillin against both gram‐negative and gram‐positive bacteria. These results revealed the prospects for the application of chitosan‐capped silver nanoparticles to create new effective antibacterial systems (gels, films, etc).

In this work, new chitosan derivatives (CS1-CS6) were obtained by short-term hydrothermal treatment. The formation of chitosan derivatives occurred through two simultaneous processes: hydrolysis and Maillard self-reaction. The synthesized chitosan-based Maillard self-reaction products were characterized by physical measurements and spectroscopic methods (viscometry, UV–Vis, FTIR, 1H NMR, TGA and XRD). The results showed that hydrothermal treatment of chitosan solutions leads to a significant decrease (from ∼ 66500 up to ∼ 20150 Da) in the viscosity-average molecular weight of polymer. It has been shown that the antiradical activity of CS1-CS6 was 2-5 times higher in comparison with the activity of unmodified chitosan (1.42 µg ascorbic acid equivalents/mg). The enhanced (R value ≥ 4-5) antimicrobial activity of CS1-CS5 derivatives against gram-negative and gram-positive bacteria including thermophilic highly heat-resistant Geobacillus stearothermophilus has been demonstrated.

In the present study, we report the development of poly (vinyl alcohol) (PVA) and chitosan oligosaccharide (COS)-based novel blend films. The concentration of COS was varied between 2.5–10.0 wt% within the films. The inclusion of COS added a brown hue to the films. FTIR spectroscopy revealed that the extent of intermolecular hydrogen bonding was most prominent in the film that contained 5.0 wt% of COS. The diffractograms showed that COS altered the degree of crystallinity of the films in a composition-dependent manner. As evident from the thermal analysis, COS content profoundly impacted the evaporation of water molecules from the composite films. Stress relaxation studies demonstrated that the blend films exhibited more mechanical stability as compared to the control film. The impedance profiles indicated the capacitive-dominant behavior of the prepared films. Ciprofloxacin HCl-loaded films showed excellent antimicrobial activity against Escherichia coli and Bacillus cereus. The prepared films were observed to be biocompatible. Hence, the prepared PVA/COS-based blend films may be explored for drug delivery applications.