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Purpose: To compare the structure and antioxidant activity of arabinoxylan (AX) extracted from wheat bran of different varieties by different methods. Methods: AX was extracted from wheat bran from the cultivars ‘Bainong 207’, ‘Baihan 207’, ‘Guanmai 1’, ‘Huayu 198’ and ‘Huayu 166’ by alkali extraction, ultrasonic-assisted xylanase extraction or ultrasonic-assisted cellulase extraction, and its chemical composition, relative molecular mass, molecular structure, thermal stability and antioxidant activity were determined. Results: Among the three extraction methods, alkali extraction gave higher levels of AX yield and total sugar content, while enzymatic extraction retained polyphenols to a greater extent, which may contribute to the better antioxidant capacity of the AX-rich extract, but reduced the relative molecular mass of AX to a certain extent. The monosaccharide composition of enzymatically extracted AX was significantly different from that of alkali extracted AX, and the glycosidic linkage types in enzymatically extracted AX were more complex. Compared with ultrasonic-assisted cellulase extraction, higher AX yield and total sugar content were obtained using ultrasound-assisted xylanase, while the polyphenol content of AX obtained by ultrasound-assisted cellulase extraction was higher, and monosaccharide composition and glycosidic linkage types were also different between AXs extracted by the two enzymatic methods. In addition, the relative molecular mass, the monosaccharide composition, and the types and proportions of glycosidic linkage of AX extracted from wheat bran of different varieties were different. Conclusion: The structure and activity of AX extracted from wheat bran by alkali extraction, ultrasonic-assisted xylanase extraction and ultrasonic-assisted cellulase extraction were obviously different. Compared with alkali extraction, AX obtained by enzymatic extraction had lower yield and molecular mass, but higher polyphenol content and better antioxidant performance. Compared with ultrasound-assisted cellulase extraction, AX obtained by ultrasound-assisted xylanase extraction had higher yield and total sugar content, but lower polyphenol content. The structure of wheat bran AX varied with different extraction methods and varieties.

In this study, a high molecular weight arabinoxylan (AX, Mw: 694 kDa) from wheat bran was alkaline extracted and covalently linked with Catechin (CA) by free radical catalytic reaction. Comparing to AX, arabinoxylan-catechin (AX-CA) conjugates demonstrated an extra UV–vis absorption peak at 274 nm, a new FT-IR absorption band at 1516 cm−1 and new proton signals at 6.5–7.5 ppm, which all confirmed the covalently linked structure. Grafting CA onto AX not only decreased the molecular weight, thermal stability and apparent viscosity of AX, but also enhanced its inhibition effects on starch digestibility in vitro. The in vitro fermentation test with pig feces showed that the degradation & utilization rate of AX, the total short-chain fatty acid (SCFA) and acetic acid levels produced all were significantly delayed after grafting. This study provided a novel approach to synthesize AX-CA conjugates that could be a novel dietary fiber of enhanced functional/bioactive properties using in the fields of functional foods and medicine. [ABSTRACT FROM AUTHOR]

Corn bran hemicellulose was extracted from de-oiled and de-starched corn bran using 0.3 M alkali at 120 °C. Following neutralization, ethanol (75%) precipitation, dialysis, protein digestion, re-precipitation in ethanol, and freeze-drying, purified corn fiber gum (PCFG) was obtained in overall yield of 45.96%. PCFG gave a single peak by high performance size exclusion chromatograph, and had average molecular weight of 296 kDa. Monosaccharide composition, methylation, and GC–MS analysis indicated that PCFG was comprised of three monosaccharides, arabinose (ara f), xylose (xyl p) and galactose (gal p) with the following linkage: t-ara f , 17.09%; 1,3-ara f , 12.43%; t-xyl p , 16.13%; 1,4-xyl p , 11.57%; 1,3,4-xyl p , 26.02%; 1,2,3,4-xyl p , 10.46%; t-gal p , 6.37%. Partial acid hydrolysis suggested that arabinofuranose sugar residues were substituted onto a 1,4-linked xylan backbone. Extensive 1D and 2D NMR spectroscopy was used to identify and confirm the following linkages: t-xyl p , 1,2,3,4-β-D-xyl p, t-α-L-ara f , 1,2-α-L-ara f and 1,4-β-D-xyl p. Several other linkage fragments were also deduced: t-ara f →2-ara f →2- O -(1,3,4-xyl), t-ara f →2-ara f →3- O -(1,2,4-xyl), t-ara f →2-ara f →3-ara f, and t-gal→2-ara. Image 1 • Purified corn fibre gum (PCFG) was extracted from corn bran. • Major monosaccharides in PCFG were arabinose, xylose, and galactose. • Glyosidic linkages in PCFG were identified by NMR and methylation analysis. • Monosaccharide sequence was determined by partial hydrolysis and NMR. [ABSTRACT FROM AUTHOR]

Hemicellulose fraction from dried distillers grains with solubles (DDGS) was isolated and its molecular structural and conformational properties were elucidated by using partial acid hydrolysis, methylation analysis and NMR spectroscopy. Using 0.3 M sodium hydroxide (120 °C), a purified water soluble hemicellulose molecules (HFG) was isolated from de-oiled and de-starched DDGS. The yield of HFG was up to 27% (w/w). Results from monosaccharide composition, methylation analysis indicated that HFG comprised three types of sugar residues: arabinose based sugar residues including t-Ara f (28.6 mol%) and 1,3-Ara f (4.9 mol%); xylose based sugar residues including t-Xyl p (14.1 mol%), 1,4-Xyl p (18.6 mol%), 1,3, 4-Xyl p (20.8 mol%), and 1,2,3,4-Xyl p (6.8 mol%); and galactose based sugar residue including t-Gal p (6.1 mol%). Partial acid hydrolysis combined with high performance size exclusion chromatography (HPSEC) indicated that protein (4.69%) was covalently linked with carbohydrate portion in HFG, which can be potentially used as food emulsifiers. Although HFG had a high substitution degree (75%), it was a more rigid molecule compare to gum arabic, indicating a shorter branching chain of HFG. 1D and 2D NMR spectroscopy confirmed the presence of t-xyl p , 2,3,4-β-D-xyl p, t-α-L-ara f , 3-α-L-ara f and 4-β-D-xyl p and several linkage fragments were deduced: t-ara f →2-ara f →2- O -(1,2,3,4-xyl), t-ara f →2-ara f →3- O -(1,2,3,4-xyl), t-ara f →2-ara f →3-ara f and t-gal→2-ara. The information gained from this study could help us to better understand the properties of hemicellulose and its performance in applications. [ABSTRACT FROM AUTHOR]

In this study, arabinoxylan (AX) isolated from wheat bran was used to prepare AX-fortified bread and biscuits, and the effects of the amount and method of AX addition on the nutritional properties of baked products were investigated through simulated digestibility and colonic simulated fermentability analysis in vitro. The purified AX demonstrated a high total sugar content (92.75%), high molecular weight (Mw) (669.8 kDa), low polymer dispersity index (PDI) and low arabinose to xylose (A/X) ratio (1.21). In vitro digestibility test indicated that AX addition could dose-dependently inhibit the starch digestibility in both bread and biscuits. Most importantly, it could also dose-dependently transfer more starch and protein into the colon through the gastrointestinal tract, leading to the changes in total amount and chemical composition of food residues. Results from the in vitro fermentability test showed that alterations in the composition of food residue affected its fermentability: a high relative ratio of carbohydrate to protein could enhance its prebiotic effect. This study provides valuable insights into the role of dietary fibres in baked foods, aiming to achieve precise nutrition for high-fibre food products. [Display omitted] • Arabinoxylan (AX) added to baked food dose dependently inhibited the rate of starch hydrolysis. • The starch digestibility in bread/biscuits prepared by mixing AX with flour is lower. • AX-fortified breads/biscuits translocate more starch and protein into the colon, affecting its fermentability. • A high relative ratio of carbohydrate to protein in colon could enhance its prebiotic effect. [ABSTRACT FROM AUTHOR]

This study explored the effects of wheat bran arabinoxylan (AX) of various molecular structures on the functional and in vitro digestibility of wheat starch. AX was separated with sequential ethanol precipitation into different fractions (L-Fra and H-Fra), followed by acidic treatment at varied time to convert L-Fra into different subfractions (H-Sub, M-Sub and L-Sub), and the structural features of AX and its subsequent fractions were compared. The Mw and branching degree of the fractions were decreased in the order of H-Fra (545 kDa, 1.15), L-Fra (86 kDa, 0.35), H-Sub (38 kDa, 0.16), M-Sub (21 kDa, 0.10) and L-Sub (7 kDa, 0.08). The functional properties, such as pasting properties, rheological properties, thermal properties, and their effect on the in vitro digestibility of wheat starch-AX combinations, were closely related to the molecular structures of AX. AX with higher Mw, higher branching degree and phenolic content could better inhibit the starch gelatinization and retrogradation, thus reducing the apparent viscosity and gelling properties of wheat starch. The possible mechanisms can be illustrated as 1) AX could compete for water with starch to inhibit granule expansion; 2) AX could not only adsorb on the surface of starch granules through hydrogen bonds but also entangle with the leached amylose and wrap on the surface of granules; 3) AX contained phenols, leading them to inhibit granule expansion through non-covalent interactions with starch molecules. Overall, this study provides a theoretical basis to improve the quality of wheat starch foods and extend the shelf life of wheat foods. [Display omitted] • Arabinoxylan (AX) fractions with various structural features were obtained. • The molecular weight (Mw), degree of branching (DOB) and phenols of AX were explored. • AX with higher Mw, higher DOB and phenols could better inhibit starch gelatinization. • AX with higher Mw, higher DOB and phenols could better inhibit starch retrogradation. • All AX with various structures could inhibit the in vitro digestibility of starch. [ABSTRACT FROM AUTHOR]

Ferulic acid (FA) of various ratios was successfully tagged onto arabinoxylan (AX) molecule by N,N′-carbonyldiimidazole (CDI) radical grafting reaction. The structural characterization of conjugates was conducted using methylation analysis, UV–vis, FT-IR and 1H NMR spectroscopy. The linkage patterns of AX before and after conjugation were similar. However, tagging FA onto AX significantly decreased the water solubility & Mw, whereas the apparent viscosity & antioxidant activity of AX were significantly enhanced. All these changes were positively correlated with the degree of attached FA. This study showed that trace amounts of phenolic compounds play a critical role in affecting the functional and bioactive properties of non-starch polysaccharides, which pave the way to develop novel dietary fibres with targeted functional and/or physiological properties. [Display omitted] • AX-FA conjugates of various FA ratios were prepared by CDI radical reaction. • The water solubility and Mw of conjugates were decreased. • The viscoelasticity and antioxidant activities of AX were improved by grafting reaction. [ABSTRACT FROM AUTHOR]

• Arabinoxylan was fluorescently labeled by DMSO/DBTD and reductive amination methods. • The solubility of conjugates was decreased with increasing degree of substitution. • The conjugates had a higher Mw and similar monosaccharide composition compared to AX. • The chain conformation of conjugates became more compact after labeling. Three fluorescent-labeling methods, including DMSO/DBTD, reductive amination and fluoresceinamine (FA), were applied to label arabinoxylan (AX). The conjugates were named AF, ATF and ACF, respectively. Compared to AX, the water solubility of AF significantly decreased while that of ATF significantly increased (p < 0.05); both showed decreased solubility with increasing degree of substitution (DS). However, AX was not successfully labeled by the FA method due to poor solubility. The structural and conformational properties of the AF and ATF conjugates under different DS were compared. Results showed that fluorochrome (FITC) was successfully grafted onto AX molecule by using the DMSO/DBTD and reductive amination methods. A slight increased Mw was noticed for both AF and ATF. AF existed in a more compact conformation, while the chain conformation of ATF was more elongated at a lower DS (1.15 %) and more compact at a higher DS (1.34 %). [ABSTRACT FROM AUTHOR]

Ultrasonication, xylanase and trifluoroacetic acid (TFA) treatments were applied to modify wheat bran arabinoxylan (AX) molecules. Molecular weight (Mw) distribution analysis, methylation analysis, rheological analysis and starch in vitro digestibility test were followed to compare the structural and functional properties of AX under different treatments. Different degradation methods decreased the Mw of AX in distinct manners, resulting in fractions with different structural features. Ultrasound treatment decreased the Mw of AX (640 kDa) to medium size range (640–100 kDa) with a slightly decreased degree of branching (DOB). Xylanase and TFA treatments could generate fragments with relative lower Mw (<100 kDa) compared to ultrasound treatment. However, sugar residues of AX from xylanase treatment showed a much higher DOB (47.89) and better solubility than those from TFA treatment. AX of larger Mw fractions showed higher apparent viscosity under the shear rate (50.3/s) close to the value induced by gastrointestinal peristaltic. In vitro digestion experiments of AX-starch mixture and AX fortified bread both showed that the higher Mw of the AX demonstrated a better inhibitory effect against starch digestibility, leading to a higher percentage of resistant starch. According to differential scanning calorimetry (DSC) analysis, AX could inhibit the retrogradation of wheat starch during bread storage, which provides complementary information for the above-mentioned conclusions. Image 1 • Three arabinoxylan fractions with different molecular weight were obtained. • The structural and functional features of different fractions were investigated. • All fractions showed inhibition on in vitro digestibility of starch and bread. • All fractions could inhibited the retrogradation of bread during storage. [ABSTRACT FROM AUTHOR]