The effect of in vitro digestion on the interaction between polysaccharides derived from Pleurotus eryngii and intestinal mucus.

Pleurotus eryngii polysaccharides (PEPs) have been proven to display multiple activities through digestive system action, from which the digestion products should first interact with intestinal mucus (MUC), followed by the function of intestinal cells. Hence, possible interacting characterizations between MUC and in vitro simulated digestion products of P. eryngii polysaccharides (DPEPs) and PEP were carried out in the present study. Results showed that both PEP and DPEP could significantly interact with MUC. Moreover, digestion can modify the interaction between polysaccharides and MUC; the degree of interaction also changes with time incrementing. Viscosity could be decreased after digesting. According to the zeta potential and stability analysis result, the digestive behavior could be regular and stable between polysaccharides and MUC interactions. Following fluorescence and infrared spectra, the structure of polysaccharides and mucin might be changed by digestion between polysaccharides and MUC. The study indicates that the interaction formed between DPEP and MUC might indirectly impact the exercise and immune activities of polysaccharides and influence the transportation of other nutrients. Overall, our results, the absorption and transport pathways of PEP, can be initially revealed and may provide a novel research viewpoint on the active mechanism of PEP in the intestinal tract.

The structure-activity mechanism of the changes in the physicochemical properties of Flammulina velutipes polysaccharides during ultrasonic extraction.

BACKGROUND: The high yield of ultrasonic extraction has been widely studied. However, the effects of ultrasound on the properties of products has generally been ignored. In this study, the structural characteristics, rheological properties, and thermal stability of Flammulina velutipes polysaccharides (FVPs) under different ultrasonic power (200, 600, 1000 W) and time (10, 20, 30 min) were investigated to explore the effects of ultrasonic extraction on FVPs and the structure-physicochemical properties relationship. The ultrasonic intensity at the corresponding rated power was also measured. RESULTS: The results showed that the molecular weight, particle size, and zeta potential of FVPs decreased as the ultrasonic intensity or time increased. The galactose, mannose, and fucose contents were increased, but the glucose content was decreased by ultrasonic extraction. Viscosity and weak gel strength were positively correlated with molecular weight. Thermal degradation enthalpy was positively correlated with the galactose and fucose contents. CONCLUSIONS: Ultrasound reduced the viscosity and gel strength of FVPs by breaking the polysaccharide chain and improving the galactose and fucose contents, which improved the thermal stability of FVPs. This work provides a theoretical basis for the development of FVP foods with a clear structure-function relationship, which makes it possible to directionally produce FVPs by adjusting ultrasonic parameters during extraction. © 2021 Society of Chemical Industry.

Storage Quality Variation of Mushrooms (Flammulina velutipes) after Cold Plasma Treatment.

Flammulina velutipes is susceptible to mechanical damage, water loss, microbial growth, and other factors that lead to postharvest deterioration, thereby shortening the storage period. The purpose of this study was to analyze the effects of cold plasma treatment on the physicochemical properties and antioxidant capacity of F. velutipes during storage at 4 °C for 21 days. Compared to the control group, cold plasma cold sterilization (CPCS) treatment (150 Hz, 95 kV for 150 s) effectively inhibited the growth and multiplication of microorganisms on the surface of F. velutipes, with no significant effect on the fresh weight change and the superoxide anion generation rate, but with a higher postharvest 1,1-dephenyl-2-picrylhydrzyl (DPPH) clearance rate. Moreover, CPCS increased antioxidant enzyme activities, delayed both malondialdehyde (MDA) accumulation and vitamin C loss, inhibited the browning reaction and polyphenol oxidases (PPO) activity and protected F. velutipes cell membrane from disruption. In general, CPCS not only achieved bacteriostatic effects on F. velutipes during storage, but also reduced cell damage from free radical oxidation, resulting in better postharvest quality and longer shelf life.

Preparation of newly identified polysaccharide from Pleurotus eryngii and its anti-inflammation activities potential.

The anti-inflammatory effects of two newly identified Pleurotus eryngii polysaccharides (WPEP, NPEP) were determined in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in this study. Characterization analysis revealed that molecular weights of WPEP and NPEP were 167 and 274 kDa, and were mainly composed of glucose with ß-type glycosidic linkages. WPEP and NPEP could significantly inhibit LPS-induced inflammatory responses by regulating the production of NO, Protaglandin E2 (PGE2 ), Interleukin-1ß (IL-1ß), Tumor necrosis factor-α (TNF-α), and Interleukin-6 (IL-6). This was through the blocking of the activation of Mitogen-activated protein kinase (MAPK) pathway by inhibiting phosphorylation of p38, extracellular regulation of protein kinases 1/2, and stress-activated protein kinase/jun aminoterminal kinase. Moreover, WPEP and NPEP inhibited NF-κB signaling by reducing nuclear translocation and phosphorylation of p65. Overall, our results, for the first time identified two P. eryngii polysaccharides and demonstrated the related anti-inflammatory effects, which indicated the favorable potential of P. eryngii polysaccharide as specific functional foods. PRACTICAL APPLICATION: This study prepared and characterized newly identified Pleurotus eryngii water-soluble polysaccharide fractions and elucidated the nutritional benefits, mainly the immune response related to anti-inflammatory activities by utilizing lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Collectively, results of this study suggested that the P. eryngii polysaccharide fractions could be considered as potential candidates for exploration in the development of new immunomodulatory agent or functional supplementary foods.

Effects of ultrasound-assisted extraction on antioxidant activity and bidirectional immunomodulatory activity of Flammulina velutipes polysaccharide.

In order to investigate the impacts of ultrasound-assisted extraction (UAE) on Flammulina velutipes polysaccharides (FVPs), the differences between FVPs extracted by ultrasound-assisted extraction (FVPU) and FVPs extracted by hot water extraction (FVPH) were compared in terms of yield, primary compositions, surface microstructure, helix-coil transition structure, molecular weight distribution, antioxidant activity, and bidirectional immunomodulatory activity. Results indicated that UAE changed the above properties of FVPs. Compared with FVPH, higher yield, protein content, and uronic acid content but lower polysaccharide and polyphenol contents were observed in FVPU. UAE changed the surface microstructure, destroyed the triple helix structure, and increased the proportion of low molecular weight polysaccharide components of FVPU. Compared with FVPH, FVPU showed a stronger reducing power and scavenging activities on DPPH radical, hydroxyl radical, and superoxide anion radical. FVPU was a better inhibitor of inflammation compared with FVPH. However, FVPH had a better immunity enhancing effect compared with FVPU. These results were attributed to the cavitation effect of ultrasonic waves on the structure of polysaccharides during the extraction process of UAE. These findings suggested that UAE was an efficient and environmentally friendly method to produce new polysaccharides from F. velutipes for the development of functional foods or nutraceuticals.

Impacts of Dietary Pleurotus eryngii Polysaccharide on Nutrient Digestion, Metabolism, and Immune Response of the Small Intestine and Colon-An iTRAQ-Based Proteomic Analysis.

Pleurotus eryngii polysaccharides have been shown to exert significant biological activities to the host. However, few studies have been conducted on its effects on gastrointestinal tract (GIT) health alteration. In the present study, small intestinal and colonic proteome alterations generated by dietary supplementation with a novel homogeneous P. eryngii polysaccharide (PEP) in C57BL/6 mice, based on the isobaric tag for relative and absolute quantification (iTRAQ) proteomics, are investigated. Compared to the control group, PEP supplementation result in a total of 113 and 194 significant differential proteins (DPs) in the small intestine and colon, respectively. Interestingly, DPs in small intestine are mainly related to the transport and biosynthetic process, along with the digestion and absorption pathway of nutrients, whereas the colonic DPs are significantly found participating in numerous metabolic processes. Moreover, the alterations of some DPs in small intestine and colon are speculated to correlate with the colonic microbiota structure and are involved in the regulation of host immune response. Subsequently, some critical DPs of small intestine and colon are selected and validated by Western blotting. The current research facilitated the generation of potential insights into the health benefit activities and functional mechanisms of polysaccharides from P. eryngii.

In vivo fermentation of a Pleurotus eryngii polysaccharide and its effects on fecal microbiota composition and immune response.

A novel, homogeneous Pleurotus eryngii polysaccharide (PEP) (molecular weight 426 kDa, purity 91.25 ± 3.14%) which mainly consisted of glucose with ß-type glycosidic linkages was used to investigate in vivo fermentation behavior and effects on immune response in mice. Different doses (0.2, 0.4, 0.8 g per kg body weight) were orally administered to the mice for a period of six weeks. The results showed that the SCFA concentration, pH value, and moisture contents of cecum and colon contents were significantly altered with high-dose PEP treatment compared to the control group (P < 0.05). Moreover, the fecal microbiota in the PEP treated group was found to be structurally different compared to the control group; especially, the Porphyromonadaceae, Rikenellaceae, Bacteroidaceae and Lactobacillaceae abundances were all increased at the family level. In addition, the exerted immune response was significantly altered after the high-dose PEP oral administration. This exploratory study indicated that intake of PEP could have a positive role in gastrointestinal tract health.

Comparison of flavour qualities of mushrooms (Flammulina velutipes) packed with different packaging materials.

To clarify the dynamic changes of flavour components in mushrooms packed with different packaging materials during storage, comprehensive flavour characterization, non-volatile and volatile compounds of Flammulina velutipes were evaluated using electronic nose (E-nose), electronic tongue (E-tongue) technology and headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. Results showed that volatile compounds of fresh F. velutipes mainly consisted of ketones and alcohols, with 3-octanone being the predominant compound. After storage, volatile components significantly changed in mushrooms packed with normal packaging material (Normal-PM) according to the GC-MS analysis and radar fingerprint chart of electronic nose. The ethanol accumulation was inhibited by nanocomposite packaging materials (Nano-PM). Besides, both radar graph and PCA of E-tongue signals could differentiate the samples from different packaging and storage time. In general, these results may provide a profile of flavour substances and explain mechanism of flavour changes in F. velutipes over storage period.

Antioxidant potential of edible mushroom (Agaricus bisporus) protein hydrolysates and their ultrafiltration fractions.

Mushroom protein isolate (MPI) from Agaricus bisporus was hydrolyzed using Alcalase, Pancreatin, Flavourzyme, Alcalase-Pancreatin and Alcalase-Flavourzyme. The obtained hydrolysates (MPHs) were ultrafiltered to generate peptide fractions (UFs) of molecular sizes (<1, 1-3, 3-5 and 5-10kDa). The electrophoretic profile results indicated that the enzymatic systems were efficient in hydrolyzing the MPI into low molecular weight peptides. Hydrolysate yields of >57% and protein recoveries of >43% were obtained. Effective concentration that scavenged 50% (EC50) of DPPH radicals was similar for the MPHs while inhibition against linoleic acid oxidation was strongest (66.49%) for Alcalase-Flavourzyme hydrolysate on day 5 of incubation. UFs exhibited a concentration-dependent FRAP, with the highest activity for fractions from Alcalase and Pancreatin recorded in 1-3kDa. The antioxidant activities of MPHs and their UFs suggested that they could be potential bioactive ingredients for use in the formulation of functional foods as well as natural antioxidants in lipid food systems.

The Correlation Between In Vitro Antioxidant Activity and Immunomodulatory Activity of Enzymatic Hydrolysates from Selenium-Enriched Rice Protein.

The antioxidant and immunomodulatory activities of selenium-enriched rice protein hydrolysates (Se-PH) were evaluated by a cellular antioxidant activity test and macrophage proliferation and phagocytosis assays, respectively. The results showed that trypsin hydrolysate provided the highest proliferation rate of 60.91% at a concentration of 100 µg/mL. Moreover, a remarkable rise in the phagocytosis rates for trypsin hydrolysate (64.1%) and pepsin-trypsin hydrolysate (54.5%) was observed when the sample concentrations were increased to 50 µg/mL. A positive correlation was found between the phagocytic ability of macrophages and both the selenium concentration and the degree of hydrolysis of Se-PH, and the correlation coefficients R obtained were 0.792 and 0.930 (P < 0.05), respectively. The capacity of Se-PH to inhibit the oxidation of dichlorodihydrofluorescein had a significant negative correlation with the phagocytic ability of macrophages (R = -0.840, P < 0.05). In conclusion, a positive correlation was found between the antioxidant activity and the immunomodulatory activity of Se-PH, which could be used as potential functional food additives for improving human health.

Protection mechanism of Se-containing protein hydrolysates from Se-enriched rice on Pb2+-induced apoptosis in PC12 and RAW264.7 cells.

This study aimed to investigate the protection mechanism of Se-containing protein hydrolysates (SPH) from Se-enriched rice on Pb2+-induced apoptosis in PC12 and RAW264.7 cells. Results showed that SPHs could alleviate Pb2+-induced morphological changes of apoptosis and the loss of mitochondrial transmembrane potential in both cell types. Besides this, SPHs could significantly reduce the activation of caspase-3, -8, -9 induced by Pb2+, reverse the Pb2+-induced upregulation of Bax and release of cytochrome C, and downregulate Bcl-2 in cells. HPLC-ICP-MS and SEC-HPLC assays showed that SPHs were low molecular weight peptides (229.4-534.9Da), and the major Se species found in SPHs was SeMet. Taken together, these findings suggested that SPHs could possibly protect the cells against Pb2+-induced apoptosis via a caspase-dependent mitochondrial pathway, and the primary effective constituents in SPHs were SeMet and Se-containing peptides, suggesting that SPHs might be a novel potential candidate to improve the health of people with Se deficiency or in Pb-contaminated areas.

Development, physiochemical characterization and forming mechanism of Flammulina velutipes polysaccharide-based edible films.

Edible films of Flammulina velutipes polysaccharide were prepared and characterized in terms of rheological, optical, morphologic, mechanical and barrier properties to evaluate their potential application in food packaging. Results suggested that FVP film prepared by the solution of 1:150 (w/v) had the optimal mechanical property, smooth and uniform surface, and good barrier property to water (37.92±2.00gmm/m(2)hkPa) and oxygen (37.92±2.01meq/kg). The capacity of film-formation might be related to inter-molecular and intra-molecular hydrogen bonds of FVP and formation of ß-glycosidic bonds during the process of film-formation. These findings will contribute to a theoretical basis for the development of FVP film in food packaging.

Identification of flavonoids from Flammulina velutipes and its neuroprotective effect on pheochromocytoma-12 cells.

The flavonoids from Flammulina velutipes (FVF) were isolated and the chemical composition of FVF was identified by high-performance liquid chromatography/mass spectrometry (HPLC/MS). The antioxidant activity and the neuroprotective effect against H2O2-induced pheochromocytoma-12 cells (PC12) cytotoxicity of FVF was investigated. Six flavonoids from FVF were identified as arbutin, epicatechin, phillyrin, apigenin, kaempferol and formononetin. Obtained results suggested that FVF possesses strong antioxidant properties in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities as well as reducing power. Pretreatment of PC12 cells with FVF significantly increased the survival rate of cells, glutathione level and superoxide dismutase activity. Conversely, the pretreatment reduced the release of lactate dehydrogenase and the accumulation of both intracellular reactive oxygen species and malondialdehyde. These findings collectively suggested that the protective effects of FVF against H2O2-induced neurotoxicity in PC12 cells as well as the potential for neuroprotection of FVF could be due to its antioxidant action.

Protective effects of Se-containing protein hydrolysates from Se-enriched rice against Pb(2+)-induced cytotoxicity in PC12 and RAW264.7 cells.

The protective capacity of Se-containing protein hydrolysates with molecular weight below 1kDa (SPHs-3), against Pb(2+)-induced damage in PC12 and RAW264.7 cells, was investigated in this study. The cell viability, levels of reactive oxygen species (ROS), lactate dehydrogenase (LDH), superoxide dismutase (SOD), nitric oxide (NO), malondialdehyde (MDA) and glutathione (GSH) in cell were analyzed. Results showed that 100µg/ml of SPHs-3 pretreatment could significantly increase cell viability by 24.9% and 23.0% in Pb(2+)-treated PC12 and RAW264.7 cells, respectively (P<0.01). The levels of ROS, NO, LDH and MDA were reduced by 32.2%, 68.2%, 79.7% and 73.7% in 100µg/ml SPHs-3 pretreated PC12 cells, respectively (P<0.01). SPHs-3 pretreatment was also associated with increases of SOD activity and GSH content in cells. In conclusion, SPHs-3 could protect cells against Pb(2+)-induced cytotoxicity, suggesting that Se-enriched rice may be a feasible candidate to improve health standard of the Pb(2+)-pollution population.