Catabolism of Dictyophora indusiata Polysaccharide and Its Impacts on Gut Microbial Composition during In Vitro Digestion and Microbial Fermentation.

Dictyophora indusiata is one of the most famous edible mushrooms in China. D. indusiata polysaccharide (DP) has attracted increasing attention because of its multiple beneficial effects. In this study, the in vitro simulated digestion and microbial fermentation were designed to reveal the potential catabolic property of DP and its impacts on the modulation of gut microbial composition. The results showed that the reducing sugar content, total polysaccharides content, molecular weight, and rheological property of DP were not significantly altered under in vitro simulated digestive conditions. However, the molecular weight, apparent viscosity, and total polysaccharides content of indigestible DP (DPI) significantly decreased during in vitro fecal fermentation, and the reducing sugar content and the release of free monosaccharides notably increased, suggesting that DP could be degraded and used by gut microbiota. Additionally, the relative abundances of several beneficial bacteria, such as Bacteroides, Catenibacterium, Parabacteroides, and Megamonas, increased significantly, indicating that DP can regulate the composition and abundance of gut microbiota. Moreover, DP could also promote the production of SCFAs, thus changing the acid-base environment of the large intestine. The results of this study are beneficial for deeply clarifying the catabolic behavior of DP in the gastrointestinal tract, which can provide a theoretical basis for developing microbiota-directed products based on DP.

Influence of ultrasound assisted metal-free Fenton reaction on the structural characteristic and immunostimulatory activity of a ß-D-glucan isolated from Dictyophora indusiata.

The present study aimed to evaluate the influence of ultrasound assisted H2O2/ascorbic acid reaction on the structural characteristic and immunostimulatory activity of a ß-D-glucan isolated from D. indusiata, so as to reveal its potential structure-immunostimulatory activity relationship. A purified ß-D-glucan, named as DP, was quickly isolated from D. indusiata, and further identified as a 1,3-ß-D-glucan with 1,6-ß-D-Glcp as branched chains, which exhibited a rigid rod chain conformation in 0.9 % (w/v) of NaCl solution. Furthermore, results showed that the primary structure of DP was overall stable after the degradation by ultrasound assisted H2O2/ascorbic acid reaction. However, the molar mass and chain conformation of DP obviously changed. In addition, DP and its degraded products exerted remarkable immunostimulatory activity in vitro and in vivo, which could activate the nuclear factor-κB (NF-κB) signaling pathway through toll-like receptor 4 (TLR4). Indeed, the immunostimulatory activity of DP was closely-correlated to its molar mass and chain conformation. An appropriate degradation of molar mass could promote its immunostimulatory activity. While the transformation of chain conformation from rigid rod to random coil could cause the significant decrease of its immunostimulatory activity. These findings are beneficial to better understanding the structure-immunostimulatory activity relationship of ß-D-glucans from edible mushrooms.

Physicochemical and Biological Properties of Polysaccharides from Dictyophora indusiata Prepared by Different Extraction Techniques.

In this study, different extraction techniques, including traditional hot water extraction (HWE), microwave-assisted extraction (MAE), pressurized assisted extraction (PAE), and ultrasonic-assisted extraction (UAE), were used to extract Dictyophora indusiata polysaccharides (DFPs), and their physicochemical and biological properties were compared. Results revealed that extraction yields of D. indusiata polysaccharides prepared by different extraction techniques ranged from 5.62% to 6.48%. D. indusiata polysaccharides prepared by different extraction techniques possessed similar chemical compositions and monosaccharide compositions, while exhibited different molecular weights (Mw), apparent viscosities, and molar ratios of constituent monosaccharides. In particularly, D. indusiata polysaccharides prepared by HWE (DFP-H) had the highest Mw and apparent viscosity among all DFPs, while D. indusiata polysaccharides extracted by UAE (DFP-U) possessed the lowest Mw and apparent viscosity. In addition, the in vitro antioxidant effects of D. indusiata polysaccharides prepared by PAE (DFP-P) and DFP-U were significantly higher than that of others. Indeed, both DFP-P and DFP-H exhibited much higher in vitro binding properties, including fat, cholesterol, and bile acid binding properties, and lipase inhibitory effects than that of D. indusiata polysaccharides prepared by MAE (DFP-M) and DFP-U. These findings suggest that the PAE technique has good potential for the preparation of D. indusiata polysaccharides with desirable bioactivities for the application in the functional food industry.

The Chemical, Structural, and Biological Properties of Crude Polysaccharides from Sweet Tea (Lithocarpus litseifolius (Hance) Chun) Based on Different Extraction Technologies.

Eight extraction technologies were used to extract sweet tea (Lithocarpus litseifolius (Hance) Chun) crude polysaccharides (STPs), and their chemical, structural, and biological properties were studied and compared. Results revealed that the compositions, structures, and biological properties of STPs varied dependent on different extraction technologies. Protein-bound polysaccharides and some hemicellulose could be extracted from sweet tea with diluted alkali solution. STPs extracted by deep-eutectic solvents and diluted alkali solution exhibited the most favorable biological properties. Moreover, according to the heat map, total phenolic content was most strongly correlated with biological properties, indicating that the presence of phenolic compounds in STPs might be the main contributor to their biological properties. To the best of our knowledge, this study reports the chemical, structural, and biological properties of STPs, and the results contribute to understanding the relationship between the chemical composition and biological properties of STPs.

Structural Characteristics of Crude Polysaccharides from 12 Selected Chinese Teas, and Their Antioxidant and Anti-Diabetic Activities.

Twelve representative edible Chinese teas (Camellia sinensis L.) from six categories (dark tea, black tea, oolong tea, white tea, yellow tea, and green tea) were selected in this study. Tea polysaccharides (TPs) were extracted with hot water, and their structural properties and biological activities, mainly antioxidant and anti-diabetic activities, were systematically evaluated. Results revealed that the extraction yields of TPs ranged from 1.81% to 6.38%, and Pu-erh tea polysaccharides had the highest extraction yield (6.38 ± 0.28%). The chemical compositions, molecular weight, and compositional monosaccharides of TPs varied among the six categories of tea. It appeared that all TPs were protein-bound acid heteropolysaccharides, and all TPs exhibited obvious antioxidant and anti-diabetic (e.g., α-glucosidase inhibitory and antiglycation) activities. Particularly, Pu-erh tea polysaccharides also contained the highest total phenolic and protein contents, and also exhibited the best antioxidant and anti-diabetic activities. Moreover, for the structural-function relationship, the heat map analysis found that total phenolic and protein contents in TPs were positively correlated with their antioxidant and anti-diabetic activities, indicating that the presence of phenolic compounds and proteins in the TPs might be the main contributors to their bioactivities. The conclusion from this study can help understand the structural-function relationship of crude tea polysaccharides.

van der Waals epitaxial two-dimensional CdSxSe(1-x) semiconductor alloys with tunable-composition and application to flexible optoelectronics.

Despite the substantial progress in the development of two-dimensional (2D) materials from conventional layered crystals, it still remains particularly challenging to produce high-quality 2D non-layered semiconductor alloys which may bring in some unique properties and new functions. In this work, the synthesis of well-oriented 2D non-layered CdSxSe(1-x) semiconductor alloy flakes with tunable compositions and optical properties is established. Structural analysis reveals that the 2D non-layered alloys follow an incommensurate van der Waals epitaxial growth pattern. Photoluminescence measurements show that the 2D alloys have composition-dependent direct bandgaps with the emission peak varying from 1.8 eV to 2.3 eV, coinciding well with the density functional theory calculations. Furthermore, photodetectors based on the CdSxSe(1-x) flakes exhibit a high photoresponsivity of 703 A W-1 with an external quantum efficiency of 1.94 × 103 and a response time of 39 ms. Flexible devices fabricated on a thin mica substrate display good mechanical stability upon repeated bending. This work suggests a facile and general method to produce high-quality 2D non-layered semiconductor alloys for next-generation optoelectronic devices.