A Comparative Analysis Concerning The Structure And Bile Acids Binding Properties Of Soluble(1â†'3)(1â†'4)-β-D-Glucan From Three Different Cereal

Hull-less barley, one of the cereals rich in β-glucan, facilitated permanent human occupation of the Tibetan Plateau and become the main staple food crop in Tibetan Plateau today. Particularity growth environment and low production per unit area had obscured vision of researchers. But in recent years, growing attention has been paid to hull-less barley due to its specific attributes, such as high β-glucan content, which can reduce the incidence of hypercholesteremia and other metabolic disorders. With the discovery of the interaction between β-glucan and bile acids, the structural comparative analyses between hull-less barley β-glucan and others cereals β-glucan is conducive to improve the understanding of cereal β-glucan. Meanwhile, thoroughly understanding of the complexity of β-glucan structure boost the study of regularity and characteristics from the interaction between β-glucan and bile acids, which may explain the physiological activity of soluble dietary fiber in cereals.Hull-less barley β-glucan(Mn 46.16 × 104 g/mol), purified to 94.67% purity, was used in comparative analysis on structure against barley β-glucan(95.15% purity, Mn 20.19 × 104 g/mol) and oat β-glucan(95.34% purity, Mn 3.05 × 104 g/mol), and the results of primary structure proved that the oligosaccharide species of distribution were the same. The differences in the proportions of tri- and tetrasaccharides observed among different β-glucans from various sources are also reflected in the molar ratio of cellotriose to cellotetraose units(DP3:DP4), following the order of barley(2.97), hull-less barley(2.54), and oat(2.31). The results of particle size and zeta potential indicated that the β-glucan were aggregating when it was dissolved but the β-glucan was dispersed and stable again when pH decreased. Comparison of SEM and AFM images demonstrated three different cereal β-glucan share a very similar microstructure. Triple helix structure verification by Congo red showed negative results. The results of IR and NMR spectroscopy are as follows: β-glucan from three different cereals are linear homopolysaccharides of D-glucopyranosyl residues(Glcp) linked via a mixture of β-(1â†'3) and β-(1â†'4) linkages, with blocks of consecutive(1â†'4)-linked residues(i.e. oligomeric cellulose segments) separated by single(1â†'3)-linkages. In comparison with rye and wheat β-glucan, cereal β-glucan exhibited considerable diversity in their structures, including the ratio of tri- to tetramers, the amount of longer cellulosic oligomers and the molecular weight.To reduce the interference of traditional in vitro bile acids binding assays, a model for the determination of the bile acids binding capacity of soluble β-glucan was developed. In comparison with the effect of β-glucan concentrations and sources, the results inferred that the bile acids binding capacity of β-glucan was related to β-glucan gel properties. Additionally, the effect of changeable pH, different bile acid species, and different composition of bile acids on the interaction between β-glucan and bile acids follows a regular pattern, respectively. Based on the new discoveries and previous research, a new hypothesis about the mechanism of bile acids binding way of β-glucan is proposed.