Interaction between four galactans with different structural characteristics and gut microbiota.

Human gut microbiota played a key role in maintaining and regulating host health. Gut microbiota composition could be altered by daily diet and related nutrients. Diet polysaccharide, an important dietary nutrient, was one kind of biological macromolecules linked by the glycosidic bonds. Galactans were widely used in foods due to their gelling, thickening and stabilizing properties. Recently, effects of different galactans on gut microbiota have attracted much attention. This review described the structural characteristics of 4 kinds of galactans, including porphyran, agarose, carrageenan, and arabinogalactan, along with the effects of different galactans on gut microbiota and production of short-chain fatty acids. The ability of gut microbiota to utilize galactans with different structural characteristics and related degradation mechanism were also summarized. All these four galactans could be used by gut Bacteroides. Besides, the porphyran could be utilized by Lactobacillus and Bifidobacterium, while the arabinogalactan could be utilized by Lactobacillus, Bifidobacterium and Roseburia. Four galactans with significant difference in molecular weight/degree of polymerization, glycosidic linkage, esterification, branching and monosaccharide composition required gut microbes which could utilize them have corresponding genes encoding the corresponding enzymes for decomposition. This review could help to understand the relationship between galactans with different structural characteristics and gut microbiota, and provide information for potential use of galactans as functional foods.

Isolation, Physicochemical Properties, and Structural Characteristics of Arabinoxylan from Hull-Less Barley.

Arabinoxylan (HBAX-60) was fractioned from alkaline-extracted arabinoxylan (HBAX) in the whole grain of hull-less barley (Hordeum vulgare L. var. nudum Hook. f. Poaceae) by 60% ethanol precipitation, which was studied for physicochemical properties and structure elucidation. Highly purified HBAX-60 mainly composed of arabinose (40.7%) and xylose (59.3%) was created. The methylation and NMR analysis of HBAX-60 indicated that a low-branched ß-(1→4)-linked xylan backbone possessed un-substituted (1,4-linked ß-Xylp, 36.2%), mono-substituted (ß-1,3,4-linked Xylp, 5.9%), and di-substituted (1,2,3,4-linked ß-Xylp, 12.1%) xylose units as the main chains, though other residues (α-Araf-(1→, ß-Xylp-(1→, α-Araf-(1→3)-α-Araf-(1→ or ß-Xylp-(1→3)-α-Araf-(1→) were also determined. Additionally, HBAX-60 exhibited random coil conformation in a 0.1 M NaNO3 solution. This work provides the properties and structural basis of the hull-less barley-derived arabinoxylan, which facilitates further research for exploring the structure-function relationship and application of arabinoxylan from hull-less barley.

Structural characteristics and biological activities of polysaccharides from barley: a review.

Barley (Hordeum vulgare L.) is rich in starch and non-starch polysaccharides (NSPs), especially ß-glucan and arabinoxylan. Genotypes and isolation methods may affect their structural characteristics, properties and biological activities. The structure-activity relationships of NSPs in barley have not been paid much attention. This review summarizes the extraction methods, structural characteristics and physicochemical properties of barley polysaccharides. Moreover, the roles of barley ß-glucan and arabinoxylan in the immune system, glucose metabolism, regulation of lipid metabolism and absorption of mineral elements are summarized. This review may help in the development of functional products in barley.

A review of NMR analysis in polysaccharide structure and conformation: Progress, challenge and perspective.

Nuclear magnetic resonance (NMR) has been widely used as an analytical chemistry technique to investigate the molecular structure and conformation of polysaccharides. Combined with 1D spectra, chemical shifts and coupling constants in both homo- and heteronuclear 2D NMR spectra are able to infer the linkage and sequence of sugar residues. Besides, NMR has also been applied in conformation, quantitative analysis, cell wall in situ, degradation, polysaccharide mixture interaction analysis, as well as carbohydrates impurities profiling. This review summarizes the principle and development of NMR in polysaccharides analysis, and provides NMR spectra data collections of some common polysaccharides. It will help to promote the application of NMR in complex polysaccharides of biochemical interest, and provide valuable information on commercial polysaccharide products.

Protective effects of ß-glucan isolated from highland barley on ethanol-induced gastric damage in rats and its benefits to mice gut conditions.

Gastrointestinal tract disease is a global health problem which affects a major part of the world population. In this study, the gastroprotective effects of ß-glucan isolated from highland barley on ethanol-induced gastric damage in rats and its benefits to mice gut health were investigated. Biochemical and pathological analysis methods were adopted to evaluating the gastrointestinal tract protective of ß-glucan isolated from highland barley. In the ulceration model, it was found that ß-glucan treatment could mitigate the gastric lesions and gastric mucosal damage caused by ethanol, decrease the gastric ulcer index. Furthermore, ß-glucan treatment alleviated the gastric oxidative stress injury in vehicle rats through increasing the activity of superoxide dismutase and catalase, decreasing the level of malondialdehyde. In addition, ß-glucan treatment also could decrease the level of interleukin-6 and tumor necrosis factor alpha and increased level of prostaglandin E2, nitric oxide. In the mouse gut health promoting model, ß-glucan treatment increased the colon length, faces water contents and the concentration of total short-chain fatty acids (SCFAs) both in mice colon and cecum. Taken together, these results may indicate that ß-glucan isolated from highland barley exert protective effects on the gastrointestinal tract of laboratory rodents.