Isolation, structure characterization and in vitro immune-enhancing activity of a glucan from the peels of stem lettuce (Lactuca sativa).

BACKGROUND: Stem lettuce is a medicinal and edible plant. The peels, accounting for 300-400 g kg-1 raw stem lettuce and containing polysaccharides 200 g kg-1 , are discarded as industrial waste, causing environment pollution and resource waste. RESULTS: A polysaccharide named PPSL10-2 was obtained from the peels of stem lettuce after hot water extraction, and gradation with cascade ultrafiltration and purification using DEAE-Sepharose cellulose. The purity and molecular weight of PPSL10-2 is 96.10% and 2.2 × 104 Da respectively, as detected by high-performance gel permeation chromatography. PPSL10-2 was found to be an α-(1→4)-d-glucan that branched at O-6 with a terminal 1-linked α-d-Glcp as side chain, and devoid of helix conformation, which was characterized by monosaccharide composition analysis, Fourier-transform infrared spectroscopy, Congo red test, scanning electron microscopy, methylation analysis and NMR spectroscopy. Furthermore, PPSL10-2 exhibited potent immune-enhancing effect by improving proliferation and phagocytosis, promoting the secretion of nitric oxide and cytokines, as well as the expression of related genes in RAW264.7 macrophages. CONCLUSION: The findings of the present study suggest that peels as an agricultural by-product of stem lettuce are good sources of polysaccharides, which could be developed as immunopotentiator for improving human health. © 2023 Society of Chemical Industry.

Soy protein nanoparticles prepared by enzymatic cross-linking with enhanced emulsion stability.

Particle-stabilized emulsions have shown increasing potential application in food emulsion systems. Here, soy protein, an abundant and inexpensive plant-based protein, was used to develop nanoparticles for emulsion stabilizer applications. An enzymatic cross-linking method based on microbial transglutaminase (mTG) was developed for the fabrication of soy protein nanoparticles (SPNPs). The emulsion stability was compared between soy protein isolate (SPI) and three different nanoparticles. The size of SPNPs ranged from 10 nm to 40 nm, depending on the production conditions. The emulsions stabilized by SPNPs were stable for at least 20 days at room temperature, whereas the emulsion that was stabilized by SPI showed a significant creaming and phase separation phenomenon. The SPNPs also showed a higher antioxidant and reducing effect compared to SPI. The use of mTG induced cross-linking resulted in the formation of covalent bonding between protein molecules, and led to the formation of nanoparticles with higher stability. The approaches support the utilization of inexpensive and abundant plant-based resources as emulsion stabilizers in food applications.

Extraction and identification of steroidal saponins from Polygonatum cyrtonema Hua using natural deep eutectic solvent-synergistic quartz sand-assisted extraction method.

In this study, quartz sand with particularly sharp nanoscale edges acted like a nanoscale knife physically cut cells of Polygonatum cyrtonema Hua into nanosized particles and was synergized with natural deep eutectic solvent to extract steroidal saponins of Polygonatum cyrtonema Hua. The natural deep eutectic solvent (choline chloride-lactic acid)-synergistic quartz sand-assisted extraction was optimized using response surface methodology. The steroidal saponins purified with AB-8 macroporous resin were identified using ultra-high-performance liquid chromatography-triple time of flight mass spectrometry. The results showed that the experimental total saponins content value (36.97 ± 0.12 mg dioscin equivalent/g dry weight) at optimal extraction conditions with a temperature of 68°C, a rotational speed of 20 400 rpm, shear time of 4.3 min, the liquid-solid ratio of 38 ml/g, was close to the maximum possible theoretical value (36.64 mg dioscin equivalent/g dry weight). A total of 20 steroidal saponins were identified, among which the content of (25R)-Kingianoside E was the highest (102.66 ± 3.47 mg/g). Furthermore, a new steroid saponin (3ß,25S)-26-(ß-D-glucopyranosyloxy)-22-hydroxyfurost-5-en-3-yl 4-O-ß-D-glucopyranosyl-ß-D-galactopyranoside+Glc was found for the first time. These results revealed that natural deep eutectic solvent-synergistic quartz sand-assisted extraction was an efficient and green method to extract a variety of steroidal saponins.

Synergistic Antitumor Effect of Grifola frondose Polysaccharide-Protein Complex in Combination with Cyclophosphamide in H22 Tumor-Bearing Mice.

Hepatocellular carcinoma (HCC) is the most common type of liver malignancy and remains a global health threat. The objective of the current study was to determine whether the combination of a cold-water extracted polysaccharide-protein complex from Grifolia frondosa (GFG) and cyclophosphamide (CTX) could inhibit tumor growth by suppressing the expression of angiogenesis-related proteins in H22 tumor-bearing mice. The results showed that the inhibition rate of GFG combined with CTX on H22 tumors was 65.29%, which was significantly higher than that of GFG treatment alone (24.82%). GFG combined with CTX significantly increased the expression levels of vascular endothelial growth factor, basic fibroblast growth factor, matrix metalloproteinase 2, and matrix metalloproteinase 9. Additionally, thymus index, spleen index, natural killer (NK) cell activity, interferon-γ (IFN-γ), interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) and interleukin-2 (IL-2) levels increased significantly after GFG treatment, especially after high-doses of GFG combined with CTX treatment (p < 0.05). The thymus index, spleen index, NK cell activity, IFN-γ, IL-1ß, TNF-α, and IL-2 levels were 1.90, 1.46, 1.30, 2.13, 1.64, 2.03, and 1.24 times of those treated with CTX alone. Thus, we proposed that GFG can alleviate the side effects of CTX by relieving the immunosuppressive effect, liver/renal injury, and oxidative stress. In conclusion, the combination of GFG and CTX for cancer treatment may be a promising strategy, and GFG is expected to be a potential adjuvant alternative for the treatment of HCC.

A review on chemical and physical modifications of phytosterols and their influence on bioavailability and safety.

Phytosterols have been shown to lower cholesterol levels and to have antioxidant, anti-inflammatory and other biological activities. However, the high melting point and poor solubility limit their bioavailability and practical application. It is advantageous to modify phytosterols chemically and physically. This article reviews and discusses the chemical and physical modifications of phytosterols, as well as their effects on the bioavailability and possible toxicity in vivo. The current research on chemical modifications is mainly focused on esterification to increase the oil solubility and water solubility. For physical modifications (mainly microencapsulation), there are biopolymer-based, surfactant-based and lipid-based nanocarriers. Both chemical and physical modifications of phytosterols can effectively increase the absorption and bioavailability. The safety of modified phytosterols is also an important issue. Phytosterol esters are generally considered to be safe. However, phytosterol oxides, which may be produced during the synthesis of phytosterol esters, have shown toxicity in animal models. The toxicity of nanocarriers also needs further studies.

Endoscopic retrograde appendicitis therapy versus laparoscopic appendectomy versus open appendectomy for acute appendicitis: a pilot study.

BACKGROUND: An increasing number of studies have shown the merits of endoscopic retrograde appendicitis therapy (ERAT) in diagnosing and treating acute uncomplicated appendicitis. However, no related prospective controlled studies have been reported yet. Our aim is to assess the feasibility and safety of ERAT in the treatment of acute uncomplicated appendicitis. METHODS: In this open-label, randomized trial, participants were randomly allocated to the ERAT group, laparoscopic appendectomy (LA) group and open appendectomy (OA) group. The primary outcome was the clinical success rate of the treatment. Intention-to-treat analysis was used in the study. RESULTS: The study comprised of 99 patients, with 33 participants in each group. The clinical success rate was 87.88% (29/33), 96.97% (32/33) and 100% (33/33) in the ERAT, LA and OA group, respectively. In the ERAT group, 4 patients failed ERAT due to difficult cannulation. In LA group, 1 patient failed because of abdominal adhesion. There were no significant differences among the three treatment groups regarding the clinical success rate (P = 0.123). The median duration of follow-up was 22 months. There were no significant differences (P = 0.693) among the three groups in terms of adverse events and the final crossover rate of ERAT to surgery was 21.21% (7/33). CONCLUSION: ERAT can serve as an alternative and efficient method to treat acute uncomplicated appendicitis. Trial registration The study is registered with the WHO Primary Registry-Chinese Clinical Trial Registry (ChiCTR1900025812).

Ferulic acid improves intestinal barrier function through altering gut microbiota composition in high-fat diet-induced mice.

PURPOSE: A high-fat diet (HFD) induces gut microbiota (GM) disorders, leading to intestinal barrier dysfunction and inflammation. Ferulic acid (FA) has shown anti-obesity effects, e.g., reducing body weight and food intake. However, the mechanism linking the anti-obesity effects of FA and GM modulation remains obscure. The present study aimed to clarify the mechanism underlying the anti-obesity effects of FA and modulation of the GM. METHODS: C57BL/6 J mice were fed by a low-fat diet (LFD) and HFD with or without FA at a dose of 100 mg/kg of body weight by oral gavage for 12 weeks. Using high-throughput sequencing, gas chromatography, real-time fluorescence quantitative PCR and immunohistochemical staining, the attenuation of obesity by FA were assessed via intestinal barrier integrity, inflammation, and the GM. RESULTS: FA reduced weight gain, improved HFD-induced GM imbalance, significantly enhanced intestinal short-chain fatty acid (SCFA)-producing bacteria (e.g., Olsenella, Eisenbergiella, Dubosiella, Clostridiales_unclassified, and Faecalibaculum) along with SCFA accumulation and its receptors' expression, decreased endotoxin-producing bacteria or obesity-related bacterial genera, and serum endotoxin (lipopolysaccharides), and inhibited the colonic TLR4/NF-κB pathway. Thus, FA can mitigate colonic barrier dysfunction and intestinal inflammation, induce the production of SCFAs and inhibit endotoxins by modulating the GM. CONCLUSION: These results indicate that enhancement of intestinal barrier by altering the GM may be an anti-obesity target of FA and that FA can be used as a functional compound with great developmental values.

Enhanced Antibacterial Activity of Hen Egg-White Lysozyme against Staphylococcus aureus and Escherichia coli due to Protein Fibrillation.

Antibacterial agents with broad-spectrum antibacterial properties have always been in large demand. Lysozyme, a common and inexpensive protein, is widely used in food safety and biomedical applications for antibacterial purposes. However, many pathogens are lysozyme-resistant or insensitive. In this research, we investigated the antibacterial activities and mechanism of oligomers and amyloid fibrils formed from hen egg-white lysozyme (HEWL) against Staphylococcus aureus and Escherichia coli. The HEWL fibrils showed significantly enhanced antibacterial activity against both lysozyme-resistant S. aureus and lysozyme-insensitive E. coli. The HEWL oligomers, on the other hand, did not show an obvious improvement in antibacterial activity compared to native HEWL. Our results indicated that the fibrillation of HEWL can significantly enhance antibacterial activity against both S. aureus and E. coli. The natural and inexpensive HEWL amyloid fibrils can be potentially applied to antimicrobial food packaging, animal feed, antibiotic replacement, etc.

Genome-wide identification and expression analysis of detoxification efflux carriers (DTX) genes family under abiotic stresses in flax.

The detoxification efflux carriers (DTX)/multidrug and toxic compound extrusion (MATE) transporters encompass an ancient gene family of secondary transporters involved in the process of plant detoxification. A genome-wide analysis of these transporters was carried out in order to better understand the transport of secondary metabolites in flaxseed genome (Linum usitassimum). A total of 73 genes coding for DTX/MATE transporters were identified. Gene structure, protein domain and motif organization were found to be notably conserved over the distinct phylogenetic groups, showing the evolutionary significant role of each class. Gene ontology (GO) annotation revealed a link to transporter activities, response to stimulus and localizations. The presence of various hormone and stress-responsive cis-regulatory elements in promoter regions could be directly correlated with the alteration of their transcripts. Tertiary structure showed conservation for pore size and constrains in the pore, which indicate their involvement in the exclusion of toxic substances from the cell. MicroRNA target analysis revealed that LuDTXs genes were targeted by different classes of miRNA families. Twelve LuDTX genes were chosen for further quantitative real-time polymerase chain reaction analysis in response to cold, salinity and cadmium stress at 0, 6, 12 and 24 hours after treatment. Altogether, the identified members of the DTX gene family, their expression profile, phylogenetic and miRNAs analysis might provide opportunities for future functional validation of this important gene family in flax.

Metabolic syndrome components and acute pancreatitis: a case-control study in China.

BACKGROUND: Acute pancreatitis (AP) is a common inflammatory disorder of the pancreas. Recent evidence has shown that metabolic syndrome is positively correlated with the severity of AP. However, only a few studies have revealed the relationship between metabolic syndrome and the occurrence of AP. We therefore elucidated the association between metabolic syndrome and the occurrence of AP. METHODS: A hospital-based case-control study was conducted. A total of 705 patients admitted to our hospital from January 2016 to December 2018 were included in the study. Subjects were divided into case and control groups according to their diagnosis: (1) According to the revised Atlanta classification from 2012, patients diagnosed with AP were enrolled in the case group. (2) Patients without a history of AP or any disease related to metabolic syndrome were allocated into the control group. Controls were matched to cases individually by sex and age (control/case ratio = 1). RESULTS: The incidence rate of metabolic syndrome in AP patients was 30.9%, which was more frequent than that in controls (13.2%) (OR 2.837; 95% CI 1.873-4.298, p < 0.001). In the multivariate regression analysis, a history of smoking or alcohol consumption and biliary stones were significantly associated with AP (OR 2.441; 95% CI 1.865-5.172, p < 0.001; OR 1.777; 95% CI 1.060-2.977, p = 0.029; OR 28.995; 95% CI 13.253-63.435, p < 0.001). In addition, the occurrence of AP was significantly associated with total cholesterol (TC) (OR 1.992; 95% CI 1.246-3.183, p = 0.004), triglyceride (TG) (OR 2.134; 95% CI 1.403-3.245, p < 0.001), hyperglycaemia (OR 2.261; 95% CI 1.367-3.742, p = 0.001), and apolipoprotein A (Apo A) (OR 0.270; 95% CI 0.163-0.447, p < 0.001). CONCLUSIONS: Metabolic syndrome and its components were associated with AP occurrence.

Anti-Inflammatory Effects of Mytilus coruscus Polysaccharide on RAW264.7 Cells and DSS-Induced Colitis in Mice.

Considerable literature has been published on polysaccharides, which play a critical role in regulating the pathogenesis of inflammation and immunity. In this essay, the anti-inflammatory effect of Mytilus coruscus polysaccharide (MP) on lipopolysaccharide-stimulated RAW264.7 cells and a dextran sulfate sodium (DSS)-induced ulcerative colitis model in mice was investigated. The results showed that MP effectively promoted the proliferation of RAW264.7 cells, ameliorated the excessive production of inflammatory cytokines (TNF-α, IL-6, and IL-10), and inhibited the activation of the NF-κB signaling pathway. For DSS-induced colitis in mice, MP can improve the clinical symptoms of colitis, inhibit the weight loss of mice, reduce the disease activity index, and have a positive effect on the shortening of the colon caused by DSS, meliorating intestinal barrier integrity and lowering inflammatory cytokines in serum. Moreover, MP makes a notable contribution to the richness and diversity of the intestinal microbial community, and also regulates the structural composition of the intestinal flora. Specifically, mice treated with MP showed a repaired Firmicutes/Bacteroidetes ratio and an increased abundance of some probiotics like Anaerotruncus, Lactobacillus, Desulfovibrio, Alistipe, Odoribacter, and Enterorhabdus in colon. These data suggest that the MP could be a promising dietary candidate for enhancing immunity and protecting against ulcerative colitis.

Anti-Inflammatory Properties In Vitro and Hypoglycaemic Effects of Phenolics from Cultivated Fruit Body of Phellinus baumii in Type 2 Diabetic Mice.

Dietary intervention in type 2 diabetes mellitus (T2DM) is a hotspot in international research because of potential threats to human health. Phellinus baumii, a wild fungus traditionally used as a food and medicine source, is now cultivated in certain East Asian countries, and is rich in polyphenols, which are effective anti-inflammatory ingredients useful in treatment of T2DM, with fewer side effects than drugs. To examine the hypoglycaemic effects of Phellinus baumii phenolics (PPE), the metabolite profiles of T2DM mice induced by streptozotocin after PPE intervention were systematically analyzed. Here, 10 normal mice were given normal saline as control group, and 50 model mice were randomly assigned to five groups and daily intragastric administrated with saline, metformin (100 mg/kg), and PPE (50, 100, 150 mg/kg of body weight), for 60 days. The pro-inflammatory factor contents of lipopolysaccharide stimulation of RAW 264.7 cells were decreased in a dose-dependent manner after PPE treatment, we propose that PPE could exert anti-inflammatory properties. PPE could also effectively reduce blood glucose levels, increased insulin sensitivity, and improved other glucolipid metabolism. Q-PCR results suggested that the hypoglycemic effects of PPE might be through activating IRS1/PI3K/AKT pathway in diabetic mice. These results suggest that PPE has strong potential as dietary components in the prevention or management of T2DM.

iTRAQ proteome analysis of the antifungal mechanism of citral on mycelial growth and OTA production in Aspergillus ochraceus.

BACKGROUND: Aspergillus ochraceus causes food spoilage and produces mycotoxin ochratoxin A (OTA) during storage of agricultural commodities. In this study, citral was used to inhibit A. ochraceus growth and OTA accumulation, proteomic analysis was employed to verify the mechanism of citral. RESULTS: Citral was found to significantly inhibit fungal growth and mycotoxin production in A. ochraceus. Specifically, 75, 125, 150 and 200 µL L-1 citral suppressed mycelial growth by 33%, 46%, 50% and 100%, respectively. Additionally, 75 µL L-1 citral inhibited OTA accumulation by 25%. Proteomic analysis was performed to elucidate the inhibitory mechanism of citral on mycelial growth and OTA production at subinhibitory concentrations (75 µL L-1 ). Proteomics analysis identified 2646 proteins in A. ochraceus fc-1, of which 218 were differentially expressed between control and 75 µL L-1 citral treatment samples. Differentially expressed proteins were identified by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of biological process, cellular component and molecular function terms. Potential factors affecting mycelial growth and OTA production were analysed, and OTA production was revealed to be a complex process involving many associated factors related to various processes including nutrient intake, sterol biosynthesis, ribosome biogenesis, energy metabolism, oxidative stress and amino acid metabolism. In addition, citral at 75 µL L-1 down-regulated OTA biosynthetic genes including pks and nrps, but slightly up-regulated the global regulatory factors veA, velB and laeA. CONCLUSION: The findings further demonstrate the potential of citral for the preservation of grains and other agricultural products, and provide new insight into its antifungal mechanisms at subinhibitory concentrations. © 2021 Society of Chemical Industry.

Orbitides isolated from flaxseed induce apoptosis against SGC-7901 adenocarcinoma cells.

Unique plant-derived cyclic peptides family exhibiting various key biological activities has great possibility for anticancer therapy. In this study, we investigated the effects of orbitides isolated from flax (Linum usitatissimum L.) on the growth of SGC-7901 cancer cells and the potential mechanism. Results showed that flaxseed orbitides killed off cancer cells by inducing apoptosis in a dose-dependent manner, which was confirmed by the appearance of nuclear shrinkage and DNA fragmentation, and the inhibitory effect was stronger than that of pure orbitide [1-9-NαC]-linusorb B2 or [1-9-NαC]-linusorb B3. Besides, the mitochondrial apoptosis pathway-related protein cytochrome C (Cyt C) was released from mitochondria to cytosol, associated with the activation of caspases 9 and 3, and the cleavage of PARP. Taken together, these results indicated that flaxseed orbitides induced apoptosis via the mitochondrial pathway, releasing Cyt C, increasing Bax/Bcl-2 ratio and elevating the expression of cleaved caspase 9 and 3 in SGC-7901 cells.

Physicochemical properties improvement and structural changes of bamboo shoots (Phyllostachys praecox f. Prevernalis) dietary fiber modified by subcritical water and high pressure homogenization: a comparative study.

In presented study, the effects of subcritical water (SW) and high pressure homogenization (HPH) treatments on the physicochemical and structural characteristics of dietary fibers (DFs) from bamboo shoots (Phyllostachys praecox f. Prevernalis) were investigated. The soluble dietary fiber (SDF) content was dramatically increased in SW and HPH treated DFs. Compared with HPH, SW modification enhanced higher physicochemical properties including water holding capacity (WHC), oil holding capacity (OHC) and swelling capacity (SC) of DFs. The abilities of DFs to absorb cholesterol and nitrite ions were both greatly increased after treatments. The results of Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD) showed that the structure of DFs were changed by SW and HPH. In conclusion, SW treatment showed better effects on improvement of physicochemical properties of bamboo shoot DFs than that of HPH, and the modified DFs could be a potential new functional foods or food additives.

Antibacterial Activity and Mechanisms of Essential Oil from Citrus medica L. var. sarcodactylis.

In this work, antibacterial activity of finger citron essential oil (FCEO, Citrus medica L. var. sarcodactylis) and its mechanism against food-borne bacteria were evaluated. A total of 28 components in the oil were identified by gas chromatography-mass spectrometry, in which limonene (45.36%), γ-terpinene (21.23%), and dodecanoic acid (7.52%) were three main components. For in vitro antibacterial tests, FCEO exhibited moderately antibacterial activity against common food-borne bacteria: Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus. It showed a better bactericidal effect on Gram-positive bacteria than Gram-negative. Mechanisms of the antibacterial action were investigated by observing changes of bacteria morphology according to scanning electron microscopy, time-kill analysis, and permeability of cell and membrane integrity. Morphology of tested bacteria was changed and damaged more seriously with increased concentration and exposure time of FCEO. FCEO showed a significant reduction effect on the growth rate of surviving bacteria and lead to lysis of the cell wall, intracellular ingredient leakage, and consequently, cell death.

Polymorphisms of IKZF3 Gene and Autoimmune Thyroid Diseases: Associated with Graves' Disease but Not with Hashimoto's Thyroiditis.

BACKGROUND/AIMS: The IKZF3 gene encodes a zinc-finger protein that plays an important role in the proliferation and differentiation of B lymphocytes. Autoimmune thyroid diseases (AITDs), mainly include Graves' disease (GD) and Hashimoto's thyroiditis (HT), are probably caused by the aberrant proliferation of B cells. The objective of this study was to explore the association between IKZF3 polymorphisms and AITDs. METHODS: We examined 915 AITD patients (604 GD and 311 HT) and 814 healthy controls. IKZF3 variants (rs2941522, rs907091, rs1453559, rs12150079 and rs2872507) were tested by PCR-ligase detection reaction. RESULTS: It was manifested that that the minor alleles of the five loci increased susceptibility to GD (p<0.05 for rs2941522, and p<0.01 for rs907091, rs1453559, rs12150079 and rs2872507) but in HT patients, these loci showed no significant difference compared with controls. Similarly, the genotype distributions of GD patients manifested obvious differences in all these loci compared with the control group, whereas no statistical differences were observed between HT patients and controls. Furthermore, bioinformatics tools were used to analyze rs1453559, rs12150079 and rs907091. These variants were believed to be the transcription regulator. CONCLUSION: It is the first time we reported the association between the IKZF3 polymorphisms and GD, indicating that IKZF3 gene tends to bean important risk factor for the development of GD.

Isolation and Purification of Two Isoflavones from Hericium erinaceum Mycelium by High-Speed Counter-Current Chromatography.

High-speed counter-current chromatography (HSCCC) was used to separate and purify two isoflavones for the first time from Hericium erinaceum (H. erinaceum) mycelium using a two-phase solvent system composed of chloroform-dichloromethane-methanol-water (4:2:3:2, v/v/v/v). These two isoflavones were identified as genistein (4',5,7-trihydroxyisoflavone, C15H10O5) and daidzein (4',7-dihydroxyisoflavone, C15H10O4), using infrared spectroscopy (IR), electro-spary ionisation mass (ESI-MS), ¹H-nuclear magnetic resonance (NMR) and 13C-NMR spectra. About 23 mg genistein with 95.7% purity and 18 mg daidzein with 97.3% purity were isolated from 150 mg ethanolic extract of H. erinaceum mycelium. The results demonstrated that HSCCC was a feasible method to separate and purify genistein and daidzein from H. erinaceum mycelium.

A Nanoporous Alumina Membrane Based Electrochemical Biosensor for Histamine Determination with Biofunctionalized Magnetic Nanoparticles Concentration and Signal Amplification.

Histamine is an indicator of food quality and indispensable in the efficient functioning of various physiological systems. Rapid and sensitive determination of histamine is urgently needed in food analysis and clinical diagnostics. Traditional histamine detection methods require qualified personnel, need complex operation processes, and are time-consuming. In this study, a biofunctionalized nanoporous alumina membrane based electrochemical biosensor with magnetic nanoparticles (MNPs) concentration and signal amplification was developed for histamine determination. Nanoporous alumina membranes were modified by anti-histamine antibody and integrated into polydimethylsiloxane (PDMS) chambers. The specific antibody modified MNPs were used to concentrate histamine from samples and transferred to the antibody modified nanoporous membrane. The MNPs conjugated to histamine were captured in the nanopores via specific reaction between histamine and anti-histamine antibody, resulting in a blocking effect that was amplified by MNPs in the nanopores. The blockage signals could be measured by electrochemical impedance spectroscopy across the nanoporous alumina membrane. The sensing platform had great sensitivity and the limit of detection (LOD) reached as low as 3 nM. This biosensor could be successfully applied for histamine determination in saury that was stored in frozen conditions for different hours, presenting a potentially novel, sensitive, and specific sensing system for food quality assessment and safety support.

Extraction, Structural Characterization, and Potential Antioxidant Activity of the Polysaccharides from Four Seaweeds.

Four seaweed polysaccharides were extracted from Sarcodia ceylonensis, Ulva lactuca L., Gracilaria lemaneiformis, and Durvillaea antarctica, respectively, by microwave-assisted extraction. The effect of three significant variables (extraction time, extraction temperature, and the ratio of water to raw material) on the process for extracting polysaccharides was investigated, along with the optimization of the extraction using the response surface method (RSM) with a Box-Behnken design. The polysaccharide structure, monosaccharide composition, degree of sulfation, and molecular weight (MW) distribution were analyzed by infrared (IR) spectrometry, gas chromatography (GC), and high-performance gel permeation chromatography (HPGPC). IR spectrometry showed that Sarcodia ceylonensis polysaccharide (SCP), Ulva lactuca L. polysaccharide (ULLP), and Durvillaea antarctica polysaccharide (DAP) were all sulfated polysaccharides and, except Gracilaria lemaneiformis polysaccharide (GLP), all belong to ß-pyranosidic polysaccharides. The average molecular weight (MW) of SCP, ULLP, GLP, and DAP was 466, 404, 591, and 482 kDa, respectively. The quantitative and comparative results with external standards indicated that the main monosaccharide in SCP and ULLP was mannose; and GLP and DAP were mainly composed of galactose and glucose, respectively. Then the in vitro antioxidant activity of all of the polysaccharides was evaluated using different assays-2,2-azino -bis (3-ethylbenzthiazoline-6- sulfonate) (ABTS), hydroxyl radical, nitrite scavenging capacity, and reducing power-and the relationship between their antioxidant activity and chemical characteristics were also examined. ULLP presented the highest ABTS radical scavenging activity; ULLP, SCP and DAP also showed a strong effect on the ABTS radical scavenging activity. SCP and ULLP exhibited excellent hydroxyl radical scavenging activities, about 83.33% ± 2.31% and 80.07% ± 2.17%, respectively, at 4 mg/mL. The reducing power of DAP was relatively more pronounced than that of the three other polysaccharides. However, the nitrite scavenging activities of the four seaweed polysaccharides were weaker than other antioxidant activity (ABTS), hydroxyl radical scavenging capacity, and reducing power. In addition, GLP exhibited lower activities than the other three samples in all of the tests for the antioxidant activity.