Effects of carboxymethylation, hydroxypropylation and dual‐enzyme hydrolysis combination with heating on in vitro hypoglycaemic properties of coconut cake dietary fibres

Effect of structural characteristics on the physicochemical properties and functional activities of dietary fiber: A review of structure-activity relationship

Dietary fibers come from a wide range of sources and have a variety of preparation methods (including extraction and modification). The different structural characteristics of dietary fibers caused by source, extraction and modification methods directly affect their physicochemical properties and functional activities. The relationship between structure and physicochemical properties and functional activities is an indispensable basic theory for realizing the directional transformation of dietary fibers' structure and accurately regulating their specific properties and activities. In this paper, since a brief overview about the structural characteristics of dietary fiber, the effect of structural characteristics on a variety of physicochemical properties (hydration, electrical, thermal, rheological, emulsifying property, and oil holding capacity, cation exchange capacity) and functional activities (hypoglycemic, hypolipidemic, antioxidant, prebiotic and harmful substances-adsorption activity) of dietary fiber explored by researchers in last five years are emphatically reviewed. Moreover, the future perspectives of structure-activity relationship are discussed. This review aims to provide theoretical foundation for the targeted regulation of properties and activities of dietary fiber, so as to improve the quality of their applied products and physiological efficiency, and then to realize high value utilization of dietary fiber resources.

Structural changes and molecular mechanism study on the inhibitory activity of epigallocatechin against α-glucosidase and α-amylase

In this study, the inhibition and mechanism of epigallocatechin (EGC) on two key glycoside hydrolases (α-glucosidase, α-amylase) were explored from the molecular structure level. The chemical structure of EGC was characterized by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and proton nuclear magnetic resonance spectroscopy. EGC's inhibition on these enzymes was colorimetrically determined. The effects of EGC on the chemical structure and spatial configuration of the enzymes were explored via FTIR spectroscopy, fluorescence spectroscopy, and molecular docking techniques. The results showed that EGC exhibited the inhibition of α-glucosidase and α-amylase in a non-competitive manner, showing a continuous upward trend as EGC's concentration increased. There was a fluorescence quenching effect of EGC on α-glucosidase and α-amylase. Molecular docking confirmed that EGC can bind to amino acid residues in the enzyme through intermolecular hydrogen bonds and hydrophobic interactions, resulting in the changed chemical structure and spatial conformation of the enzymes. This decreased enzyme activity. This result suggested that EGC has the potential to inhibit two key glycoside hydrolases, and it would be beneficial to incorporate EGC into functional foods for diabetics.

Effect of Particle Size on Physicochemical Properties and in vitro Hypoglycemic Ability of Insoluble Dietary Fiber From Corn Bran

This study was designed for determining the effect of particle size on the functional properties of corn bran insoluble dietary fiber (IDF). Results showed that some physicochemical properties were improved with the decrease in particle size. The structure of the IDF was observed by the scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The surface was found wrinkled and sparse, the particle size was smaller, the crystallinity of IDF had increased slightly, and more -OH and C-O groups were exposed. Moreover, the corn bran IDF with a smaller particle size had a better hypoglycemic effect in vitro, and the inhibitory activity of α-glucosidase and α-amylase were also increased significantly with the decrease in particle size (p < 0.05). When the IDF was 300 mesh, the inhibitory rate of α-glucosidase was 61.34 ± 1.12%, and the inhibitory rate of α-amylase was 17.58 ± 0.33%. It had increased by 25.54 and 106.83%, respectively compared to the control treatment (CK) group. In addition, correlation analysis found that the particle size was highly negatively correlated with some functional properties of IDF (p < 0.05), and the content of cellulose was positively correlated with the functional properties of IDF except WHC (p < 0.05). To sum up, reducing particle size was suitable for the development of high value-added IDF products. This study also revealed the potential value of corn bran IDF and provided a new idea for the diversified application of IDF.

The influences of acetylation, hydroxypropylation, enzymatic hydrolysis and crosslinking on improved adsorption capacities and in vitro hypoglycemic properties of millet bran dietary fibre

The effects of acetylation, hydroxypropylation, cellulase hydrolysis and crosslinking on adsorption capacities and in vitro hypoglycemic activities of millet bran dietary fibre (MBDF) were studied. The results demonstrated that both acetylation and hydroxypropylation improved water swelling ability of MBDF, and adsorption capacities of cholesterol, cholate and copper ion on MBDF. Acetylation and hydroxypropylation also enhanced α-glucosidase and α-amylase inhibition activities, glucose-binding ability and glucose diffusion retardation index (GDRI) of MBDF. Acetylated MBDF showed the highest cholate (77.31 mg/g) and cholesterol (13.97 mg/g) adsorption capacities. The crosslinking improved adsorption of cholate, cholesterol, copper ion (25.64 mg/g) and nitrite ion (181.59 μg/g) on MBDF; but reduced α-amylase inhibition activity (p < 0.05). Moreover, cellulase hydrolyzed MBDF exhibited the highest GDRI (39.60%) and α-amylase inhibition activity (34.53%), but the lowest oil and cholate adsorption capacities. The results suggest that the modified MBDFs can be used as an ingredient of hypoglycemic foods.

Effect of four modification methods on adsorption capacities and in vitro hypoglycemic properties of millet bran dietary fibre

To improve the adsorption capacities and hypoglycemic properties of millet bran dietary fibre (MBDF), four methods including acrylate-grafting, carboxymethylation, heat assisted with cellulase hydrolysis, and enzymatic hydrolysis combined with acrylate-grafting were used. The results demonstrated that all carboxymethylation, acrylate-grafting, and enzymatic hydrolysis combined with acrylate-grafting improved soluble dietary fibre content, water swelling ability and α-amylase-inhibition activity of MBDF. They also increased oil, cholesterol, sodium cholate, copper ion and nitrite ion adsorption capacities of MBDF. But carboxymethylation, acrylate-grafting and enzymatic hydrolysis combined with acrylate-grafting decreased polyphenol content, glucose-binding ability and glucose dialysis retardation index of MBDF (p < 0.05). The heat assisted with cellulase hydrolysis increased soluble dietary fibre content, polyphenol content, sodium cholate-adsorption capacity, and hypoglycemic properties of MBDF including glucose-binding ability, glucose dialysis retardation index and α-amylase-inhibition activity; but reduced adsorption capacity of MBDF on cholesterol and copper ion (p < 0.05). Changes in structure of MBDF caused by these modification methods were proved by the results of scanning electron microscopy and Fourier-transformed infrared spectroscopy analysis. These results highlight potential applications of these modified MBDFs as ingredients of hypolipidemic and hypoglycemic foods, or scavenger of nitrite and copper ion.