Effects of UV/H2O2 Degradation on the Physicochemical and Antibacterial Properties of Fucoidan.

The applications of fucoidan in the food industry were limited due to its high molecular weight and low solubility. Moderate degradation was required to depolymerize fucoidan. A few studies have reported that fucoidan has potential antibacterial activity, but its antibacterial mechanism needs further investigation. In this study, the degraded fucoidans were obtained after ultraviolet/hydrogen peroxide treatment (UV/H2O2) at different times. Their physicochemical properties and antibacterial activities against Staphylococcus aureus and Escherichia coli were investigated. The results showed that the average molecular weights of degraded fucoidans were significantly decreased (up to 22.04 times). They were mainly composed of fucose, galactose, and some glucuronic acid. Fucoidan degraded for 90 min (DFuc-90) showed the strongest antibacterial activities against Staphylococcus aureus and Escherichia coli, with inhibition zones of 27.70 + 0.84 mm and 9.25 + 0.61 mm, respectively. The minimum inhibitory concentrations (MIC) were 8 mg/mL and 4 mg/mL, respectively. DFuc-90 could inhibit the bacteria by damaging the cell wall, accumulating intracellular reactive oxygen species, reducing adenosine triphosphate synthesis, and inhibiting bacterial metabolic activity. Therefore, UV/H2O2 treatment could effectively degrade fucoidan and enhance its antibacterial activity.

Degradation Mechanisms of Six Typical Glucosidic Bonds of Disaccharides Induced by Free Radicals.

Increasing hydrogen peroxide (H2O2)-based systems have been developed to degrade various polysaccharides due to the presence of highly reactive free radicals, but published degradation mechanisms are still limited. Therefore, this study aimed to clarify the degradation mechanism of six typical glucosidic bonds from different disaccharides in an ultraviolet (UV)/H2O2 system. The results showed that the H2O2 concentration, disaccharide concentration, and radiation intensity were important factors affecting pseudo-first-order kinetic constants. Hydroxyl radical, superoxide radical, and UV alone contributed 58.37, 18.52, and 19.17% to degradation, respectively. The apparent degradation rates ranked in the order of cellobiose ≈ lactose > trehalose ≈ isomaltose > turanose > sucrose ≈ maltose. The reaction pathways were then deduced after identifying their degradation products. According to quantum chemical calculations, the cleavage of α-glycosidic bonds was more kinetically unfavorable than that of ß-glycosidic bonds. Additionally, the order of apparent degradation rates depended on the energy barriers for the formation of disaccharide-based alkoxyl radicals. Moreover, energy barriers for homolytic scissions of glucosidic C1-O or C7-O sites of these alkoxyl radicals ranked in the sequence: α-(1 → 2) ≈ α-(1 → 3) < α-(1 → 4) < ß-(1 → 4) < α-(1 → 6) < α-(1 → 1) glucosidic bonds. This study helps to explain the mechanisms of carbohydrate degradation by free radicals.

Insights into the mechanisms underlying the degradation of xylooligosaccharides in UV/H2O2 system.

UV/H2O2 process is increasingly used to degrade carbohydrates, though the underlying mechanisms remain unclear. This study aimed to fill this knowledge gap, focusing on mechanisms and energy consumption involved in hydroxyl radical (•OH)-mediated degradation of xylooligosaccharides (XOSs) in UV/H2O2 system. Results showed that UV photolysis of H2O2 generated large amounts of •OH radicals, and degradation kinetics of XOSs fitted with a pseudo-first-order model. Xylobiose (X2) and xylotriose (X3), main oligomers in XOSs, were attacked easier by •OH radicals. Their hydroxyl groups were largely converted to carbonyl groups and then carboxy groups. The cleavage rate of glucosidic bonds was slightly higher than that of pyranose ring, and exo-site glucosidic bonds were more easily cleaved than endo-site bonds. The terminal hydroxyl groups of xylitol were more efficiently oxidized than other hydroxyl groups of it, causing an initial accumulation of xylose. Oxidation products from xylitol and xylose included ketoses, aldoses, hydroxy acids and aldonic acids, indicating the complexity of •OH radical-induced XOSs degradation. Quantum chemistry calculations revealed 18 energetically viable reaction mechanisms, with the conversion of hydroxy-alkoxyl radicals to hydroxy acids being the most energetically favorable (energy barriers <0.90 kcal/mol). This study will provide more understanding of •OH radicals-mediated degradation of carbohydrates.

Degradation kinetic models and mechanism of isomaltooligosaccharides by hydroxyl radicals in UV/H2O2 system.

Kinetic models and mechanism of isomaltooligosaccharides (IMOs) by hydroxyl (OH) radicals-driven degradation in ultraviolet/hydrogen peroxide system were investigated. Electron paramagnetic resonance spectra indicated that UV radiation played an important role in the steady generation of OH radicals. The OH radicals could effectively decrease the molecular weight of IMOs and significantly oxidize hydroxy group into carbonyl and carboxy groups. Main components of IMOs were separated and identified by HPAEC-PAD and UHPLC-MS/MS methods. Degradation behaviors of IMOs were well fitted to pseudo first-order kinetics. The hydrogen abstraction by OH radicals from different CH sites at pyranose ring began a cascade reaction leading to cleavage of α-glycosidic linkage or CC bonds with formation of stable uronic/aldonic acids. Degradation rate was closely influenced by the degree of polymerization (DP) of IMOs, the initial concentrations of IMOs and H2O2. The results would pave the way for free radicals-driven degradation of polysaccharides.

Polysaccharides from Sargassum fusiforme after UV/H2O2 degradation effectively ameliorate dextran sulfate sodium-induced colitis.

In this study, degraded polysaccharides from Sargassum fusiforme (PSF-T2) were prepared by UV/H2O2 treatment for 2 h, and its effects on ameliorating dextran sulfate sodium-induced colitis were evaluated using a mouse model. Results showed that PSF-T2 relieved colitis symptoms, characterized by increasing the colon length and body weight, decreasing disease activity index and relieving colon damage. In addition, PSF-T2 decreased the secretion and expression of IL-1ß, IL-6 and TNF-α, and increased the expression of MUC-2, ZO-1 and occludin. Besides, PSF-T2 promoted the production of short-chain fatty acids and modulated gut microbiota composition (increasing the abundance of Lactobacillaceae, Lachnospiraceae, Oscillospiraceae and Desulfovibrionaceae, and decreasing Bacteroidaceae and Erysipelotrichaceae). These results suggested that polysaccharides from Sargassum fusiforme after UV/H2O2 degradation could ameliorate colitis by decreasing inflammation, protecting the intestinal barrier and modulating gut microbiota. It can provide a theoretical basis for the preparation of bioactive polysaccharides by free radical degradation.

Calcium-binding casein phosphopeptides-loaded chitosan oligosaccharides core-shell microparticles for controlled calcium delivery: Fabrication, characterization, and in vivo release studies.

Core-shell microparticles based on food-grade biopolymers are of particular interest for biological components delivery owing to their unique controlled release property. Here, we introduce a method to fabricate calcium-binding casein phosphopeptides (CPP)-loaded core-shell microparticles for oral calcium delivery, based on ionic gelation interactions between chitosan oligosaccharides (COS) and tripolyphosphate (TPP). The fabrication method, textural properties, calcium binding capacity, pH-dependent stability, thermal properties, intermolecular forces, morphology characterizations, the controlled calcium release and calcium absorption properties in vitro and vivo of core-shell microparticles were studied. The results showed that COS was successfully crosslinked through TPP while CPP-Ca was incorporated in it, and microparticles showed appropriate textural properties, calcium-loaded capacity, and thermal properties. Morphology observations showed the core structures were successfully coated with outer-layer COS shell. Additionally, the calcium release and absorption studies in vitro and in vivo exhibited CPP-Ca-loaded microparticles could achieve controlled calcium release and sustained calcium uptake. Therefore, the fabricated CPP-Ca-loaded core-shell microparticles could function as promising calcium supplements for enhancing calcium bioavailability.

Duck Egg White-Derived Peptide VSEE (Val-Ser-Glu-Glu) Regulates Bone and Lipid Metabolisms by Wnt/ß-Catenin Signaling Pathway and Intestinal Microbiota.

SCOPE: Val-Ser-Glu-Glu (VSEE), identified from duck egg white peptides, has been proven to facilitate calcium absorption in a previous study. Since prevention of osteoporosis is important, it might act as a potential cofactor in osteoporosis prevention. Therefore, the aim of this study is to investigate the regulation of VSEE on osteoporosis and abnormal lipid metabolisms. METHODS AND RESULTS: MC3T3-E1 cell and ovariectomized (OVX) rat model are used to evaluate VSEE on regulation of bone and lipid metabolisms. Differentiation and matrix mineralization of preosteoblast are significantly increased by VSEE (p <0.05), which attributed to stimulating calcium influx, then to activating Wnt/ß-catenin signaling pathway and regulating runt-related transcription factor 2 and osteoprotegerin. VSEE can cross Caco-2/HT-29 co-cultured monolayer via paracellular pathway and peptide transporter 1 (PepT1), and can be detected in blood and maximum concentration is 122.84 ± 3.68 mg L-1 at 60 min. Additionally, VSEE reverses bone loss and regulate dyslipidemia through Wnt/ß-catenin signaling pathway in OVX rats. Firmicutes phylum, Veillonellaceae, Prevotellaceae and six genera in VSEE group are significantly different compared with the Model group (p < 0.05). CONCLUSION: VSEE promotes bone growth and inhibit abnormal lipid metabolism in an OVX model through the regulation of intestinal microbiota compositions and Wnt/ß-catenin signal pathway.

A Comprehensive Review of Corn Protein-derived Bioactive Peptides: Production, Characterization, Bioactivities, and Transport Pathways.

Bioactive peptides are specific peptide fragments that positively exert various functional and biological activities and ultimately influence health. Corn protein are potential precursor proteins for bioactive peptides. This review encompasses the studies reported to date on the production, isolation, purification, and characterization technologies of bioactive corn peptides (CPs), with particular attention being devoted to these peptides' different health effects, including antioxidant, antihypertensive, hepatoprotective, alcohol-metabolism-facilitating, anti-inflammatory, anticancer, antimicrobial, and dipeptidyl peptidase IV (DPP-IV) inhibitory activities. The review also describes studies examining the potential mechanisms believed to be involved in these bioactivities, and the possible absorption and transport pathways of CPs are summarized.