Starch Digestive Enzymes Research Articles

Structural changes of potato starch and activity inhibition of starch digestive enzymes by anthocyanin from lingonberry (Vaccinium uliginosum L.) retarded starch digestibility

The effects of anthocyanins on in vitro and in vivo digestibility of potato starch were evaluated in this study. Then the influence of anthocyanins on physicochemical property of potato starch and the activity of starch digestive enzymes (α-amylase and α-glucosidase) were also investigated to understand the mechanism of anthocyanins on starch digestibility. Results have shown that dietary anthocyanins could effectively inhibit the biological activities of α-amylase and α-glucosidase to delay the peak of postprandial blood glucose. Characterization of physicochemical properties of potato starch indicates a structural change due to the presence of anthocyanins, hindering its access to starch digestive enzymes. Among all anthocyanins, lingonberry anthocyanin significantly promoted the retrogradation of potato starch (7.153 % to 25.913 %) and exert promising inhibition on α-amylase and α-glucosidase. Lingonberry anthocyanins mainly interacted with potato starch through hydrogen bonds, which reduce the amount of amylose molecules leached from potato starch and loosen the three-dimensional (3D) network structure of starch gel. This study could provide theoretical evidence for utilization of anthocyanins in diabetic-management function food.

Effect of Genistein on Starch Digestion In Vitro and Its Mechanism of Action.

The digestive properties of starch are crucial in determining postprandial glycaemic excursions. Genistein, an active phytoestrogen, has the potential to influence starch digestion rates. We investigated the way genistein affected the digestive properties of starch in vitro. We performed enzyme kinetics, fluorescence spectroscopy, molecular docking, and molecular dynamics (MD) simulations for analysing the inhibitory properties of genistein on starch digestive enzymes as well as clarifying relevant mechanism of action. Our findings demonstrated that, following the addition of 10% genistein, the contents of slowly digestible and resistant starches increased by 30.34% and 7.18%, respectively. Genistein inhibited α-amylase and α-glucosidase, with half maximal inhibitory concentrations of 0.69 ± 0.06 and 0.11 ± 0.04 mg/mL, respectively. Genistein exhibits a reversible and non-competitive inhibiting effect on α-amylase, while its inhibition on α-glucosidase is a reversible mixed manner type. Fluorescence spectroscopy indicated that the presence of genistein caused declining fluorescence intensity of the two digestive enzymes. Molecular docking and MD simulations showed that genistein binds spontaneously to α-amylase via hydrogen bonds, hydrophobic interactions, and π-stacking, whereas it binds with α-glucosidase via hydrogen bonds and hydrophobic interactions. These findings suggest the potential for developing genistein as a pharmacologic agent for regulating glycaemic excursions.

Inhibition of human starch digesting enzymes and intestinal glucose transport by walnut polyphenols

One approach to controlling type 2 diabetes (T2D) is to lower postprandialglucose spikesby slowing down the digestion of carbohydrates and the absorption of glucose in the small intestine. The consumption of walnuts is associated with a reduced risk of chronic diseases such as T2D, suggested to be partly due to the high content of (poly)phenols. This study evaluated, for the first time, the inhibitory effect of a (poly)phenol-rich walnut extract on human carbohydrate digesting enzymes (salivary and pancreatic α-amylases, brush border sucrase-isomaltase) and on glucose transport across fully differentiated human intestinal Caco-2/TC7 monolayers. The walnut extract was rich in multiple (poly)phenols (70 % w/w) as analysed by Folin-Ciocalteau and by LCMS. It exhibited potent inhibition of both human salivary (IC50: 32.2 ± 2.5 µg walnut (poly)phenols (WP)/mL) and pancreatic (IC50: 56.7 ± 1.7 µg WP/mL) α-amylases, with weaker effects on human sucrase (IC50: 990 ± 20 µg WP/mL), maltase (IC50: 1300 ± 80 µg WP/mL), and isomaltase (IC25: 830 ± 60 µg WP/mL) activities. Selected individual walnut (poly)phenols inhibited human salivary α-amylase in the order: 1,3,4,6-tetragalloylglucose > ellagic acid pentoside > 1,2,6-tri-O-galloyl-β-D-glucopyranose, with no inhibition by ellagic acid, gallic acid and 4-O-methylgallic acid. The (poly)phenol-rich walnut extract also attenuated (up to 59 %) the transfer of 2-deoxy-D-glucose across differentiated Caco-2/TC7 cell monolayers. This is the first report on the effect of (poly)phenol-rich extracts from any commonly-consumed nut kernel on any human starch-digesting enzyme, and suggests a mechanism through which walnut consumption may lower postprandial glucose spikes and contribute to their proposed health benefits.

Effect of Zijuan tea (Camellia sinensis var. assamica cv. Zijuan) on starch digestion properties of bread and its mechanisms

SummaryThis study investigated the effect of water extract (ZTWE) and ethanol extract (ZTEE) from Zijuan tea on the in vitro starch digestibility of bread, as well as the underlying mechanisms. Results revealed that the ZTWE and ZTEE could reduce the starch digestibility of bread, especially ZTEE, which may be due to the higher polyphenols contains in ZTEE (TPC: 233.11 mg GAE/g) than ZTWE (TPC: 195.94 mg GAE/g). Furthermore, results of enzyme activity experiments and in silico analyses demonstrated that the main four polyphenols enriched in ZTWE and ZTEE could inhibit the activities of starch digestive enzymes. Additionally, scanning electron microscopy and in silico analyses showed that the predominant polyphenols in ZTWE and ZTEE could interact with the starch molecule to alter its structure, thereby reducing the starch digestibility. These findings may offer a theoretical foundation for the development of Zijuan tea‐based functional products aimed at diabetes management.

Host species of freshwater snails within the same freshwater ecosystem shapes the intestinal microbiome

BackgroundFreshwater snails are not only intermediate hosts for parasites but also an important part of the food chain as they convert plant biomass and humus into animal biomass. However, being widely distributed in freshwater environments, snails are highly affected by human activities, which makes their adaptation to altering environments challenging. The gut microbiome helps animals in their digestion, immune system, growth and adapting to changing environments. The effect of host species on intestinal microbial community has been poorly studied in snails.MethodsIn this study, single-molecule real-time sequencing technology (SMRT) was used to obtain full-length 16S rRNA genes to determine the intestinal microbiomes of three species of freshwater snails (SQ: Sinotaia quadrata, BU: Boreoelona ussuriensis, RP: Radix plicatula) with similar feeding habits in a same water environment.ResultsUnifrac PCoA (P<0.05), hierarchical cluster and Ternary analyses showed distinct and significant segregation of the intestinal microbiomes of the three hosts. The phyla Cyanobacteria, Proteobacteria, Firmicutes and Planctomycetota dominated snail guts, comprising 93.47%, 86.22%, and 94.34% of the total reads in SQ, BU and RP, respectively. Of these, only 25.26% of OTUs were identified up to species level, while 72.07% of OTUs were identified at the genus level. Although 72.94% of the total bacterial species (566) were common to three snails, significant differences were observed in terms of their abundance (P < 0.05). Several genera can help to determine the phenotype of the intestinal microbiota. In this case, Lelliottia contributed mainly to stress tolerance, biofilm formation, potential pathogenicity, mobile elements and facultatively anaerobic phenotypes in RP. Furthermore, Romboutsia and Clostridium_sensu_stricto_1 contributed to the anaerobic phenotype of SQ and RP, while Pirellula contributed to the aerobic phenotype in SQ. Moreover, PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) predicted 68 GH (glycoside hydrolase) genes, with these including monosaccharide-, disaccharide-, polysaccharide-, and starch-digesting enzyme genes as well as enzymes specific to aquatic plants. Many of the identified pathways were related to Infectious diseases and Xenobiotics biodegradation and metabolism, which expanded the resistance of freshwater snails.ConcludesLelliottia, Romboutsia, Clostridium_sensu_stricto_1, and Pirellula play an important role in the intestinal microbiota phenotype of the host snails. In general, the host species affects the structure of the gut microbial community, which in turn helps gastropods improve their environmental adaptability, but further study is still needed.

Inhibitory effect and mechanism of tannic acid against two starch digestive enzymes

Abstract Backgrounds Tannic acid (TA), as a plant-derived phenolic substance, is involved in regulating the activity of starch digestive enzymes, but its underlying mechanism remains unclear. Methods and Results In the present study, inhibition rate and inhibition kinetics assays were performed and confirmed that TA had a strong inhibitory effect on both α-amylase and α-glucosidase with IC50 values of 0.1585 mg/mL and 0.00542 mg/mL, respectively, through a mixed inhibition mode. The secondary structures of both enzymes were confirmed to be modified by TA through circular dichroism (CD) spectra. Fluorescence quenching analysis revealed that the interaction between TA and two enzymes was a static process of pontaneous complex formation. Finally, molecular docking revealed that non-covalent bonds were the main interaction forces between TA and both enzymes. Conclusions Thus, TA was a promising candidate for the inhibition of starch-digesting enzymes, and the present research provided insight into postprandial glucose regulation through polyphenols.

A starch-binding domain of α-amylase (AmyPG) disrupts the structure of raw starch

Most raw starch-digesting enzymes possess at least one non-catalytic starch-binding domain (SBD), which enhances enzymatic hydrolysis of insoluble starch granules. Previous studies of SBD-starch interaction mainly focus on binding affinity for substrates, while the mechanism involved disruption of starch granules remains partially understood. Raw starch-digesting α-amylases AmyPG and AmyP were from Photobacterium gaetbulicola and an uncultured marine bacterium, respectively. Here, comparative studies on the two α-amylases and their SBDs (SBDPG and SBDAmyP) with high sequence identity were carried out. The degradation capacity of AmyPG towards raw starch was approximately 2-fold higher than that of AmyP, which was due to the stronger disruptive ability of SBDPG rather than the binding ability. Two non-binding amino acids (K626, T618) of SBDPG that specifically support the disruptive ability were first identified using affinity gel electrophoresis, amylose‑iodine absorbance spectra, and differential scanning calorimetry. The mutants SBDPG-K626A and SBDPG-T618A exhibited stronger disruptive ability, while the corresponding mutants of AmyPG enhanced the final hydrolysis degree of raw starch. The results confirmed that the disruptive ability of SBD can independently affect raw starch hydrolysis. This advancement in the functional characterization of SBDs contributes to a better understanding of enzyme-starch granule interactions, pushing forward designs of raw starch-digesting enzymes.

Production and characterization of intracellular invertase from Saccharomyces cerevisiae (OL629078.1), using cassava-soybean as a cost-effective substrate

The growing global market for industrial enzymes has led to a constant search for efficient, cost-effective methods for their production. This study reports the production of invertase using inexpensive and readily available agro-materials. Starch-digesting enzymes extracted from malted unkilned sorghum were used to hydrolyze cassava starch supplemented with 2% whole soybean. The production of intracellular invertase by Saccharomyces cerevisiae OL629078.1 in cassava-soybean and yeast sucrose broth was compared. The purification and characterization of invertase produced using the low-cost medium were also reported. The results showed that there was a 4.1-fold increase in the units of invertase produced in cassava-soybean medium (318.605 U/mg) compared to yeast sucrose broth medium (77.6 U/mg). The invertase produced was purified by chromatographic methods up to 5.53-fold with a recovery of 62.6%. Estimation of the molecular weight with gel filtration indicated a molecular weight of 118 kDa. The enzyme demonstrated its maximum activity at 50 °C and there was no decrease in its activity following a 1-h incubation at this temperature. At a pH of 5.0, the enzyme demonstrated optimal activity and it maintained over 60% of its activity in the acid range (pH 3–6). The Michalis-Menten constants Km and Vmax of intracellular invertase were 5.85 ± 1.715 mM and 6.472 ± 2.099 U/mg, respectively. These results suggest that Saccharomyces cerevisiae grown on cassava-soybean is a viable, cost-effective alternative for commercial invertase production, which can be explored for biotechnological processes.

Inhibitory Mechanism of Quercimeritrin as a Novel α-Glucosidase Selective Inhibitor.

In this study, 12 flavonoid glycosides were selected based on virtual screening and the literature, and Quercimeritrin was selected as the best selective inhibitor of α-glucosidase through in vitro enzyme activity inhibition experiments. Its IC50 value for α-glucosidase was 79.88 µM, and its IC50 value for α-amylase >250 µM. As such, it could be used as a new selective inhibitor of α-glucosidase. The selective inhibition mechanism of Quercimeritrin on the two starch-digesting enzymes was further explored, and it was confirmed that Quercimeritrin had a strong binding affinity for α-glucosidase and occupied the binding pocket of α-glucosidase through non-covalent binding. Subsequently, animal experiments demonstrated that Quercimeritrin can effectively control postprandial blood glucose in vivo, with the same inhibitory effect as acarbose but without side effects. Our results, therefore, provide insights into how flavone aglycones can be used to effectively control the rate of digestion to improve postprandial blood glucose levels.

Digestive enzyme corona formed in simulated gastrointestinal tract and its impact on EGCG release from banana resistant starch nanoparticles

The interaction of nanocarriers with gastrointestinal enzymes upon oral administration significantly impacts their performance as delivery systems. This work investigated the interaction between epigallocatechin gallate (EGCG) loaded into banana resistant starch nanoparticles (RSNPs) and digestive enzymes and its implications for EGCG release. The formation of a protein corona on EGCG-RSNPs in simulated gastrointestinal fluids was confirmed. The formation of this protein corona led to structural alterations in the pepsin and trypsin. Changes in enzyme conformation upon interaction with EGCG-RSNPs were elucidated using UV–Vis absorption and emission fluorescence spectroscopy. The activity of the enzymes remained largely unaffected despite these conformational changes. Additionally, the presence of the protein corona led to a slower, reduced release rate of EGCG. The results of this work will contribute to the growing knowledge of nanocarrier design for the delivery of bioactive compounds, paving the way for the development of innovative therapeutic strategies and functional foods with more excellent health benefits.

Preparation, physicochemical characterization, and in vitro starch digestibility on complex of Euryale ferox kernel starch with ferulic acid and quercetin

The objective of the current research was to analyze the physicochemical, structural, and in vitro starch digestibility of Euryale ferox kernel starch (EFKS) in complexation with ferulic acid (FA) and quercetin (QR). XRD results have shown that FA and QR were attached to starch resulting crystalline complexes. SEM image showed a smooth, compact structure, indicating FA and QR assist in the reorganization of starch molecules. The 1H NMR spectra of starch-polyphenols complexes showed multiple additional peaks between 6.00 and 9.00 ppm due to the benzene ring and phenolic hydroxyl groups imparted from polyphenols. The shifting and emergence of the characteristic peak observed in the DSC thermogram confirmed that polyphenols were successfully attached to starch. Complexation alters colors, reduced swelling power, and increased the solubility of the complexes. Following the complexation of FA and QR, the content of resistant starch exhibited a significant rise, escalating from 7.69 % (control sample) to 49.39 % (10 % FA) and 54.68 % (10 % QR). This led to a notable reduction in the predicted glycemic index (pGI).The higher resistant starch in the complex is attributed due to the combined effects of the reordered structure of the complexes and the inhibitory activity of polyphenols against starch digestive enzymes. Therefore, EFKS-FA and EFKS-QR complex can be used as a functional ingredient for a low glycemic index food.

LMA or vivipary? Wheat grain can germinate precociously during grain maturation under the cool conditions used to induce late maturity alpha-amylase (LMA).

This study found that wheat (Triticum aestivum) grain can germinate precociously during the maturation phase of grain development, a phenomenon called vivipary that was associated with alpha-amylase induction. Farmers receive severe discounts for grain with low falling number (FN), an indicator that grain contains sufficiently elevated levels of the starch-digesting enzyme alpha-amylase to pose a risk to end-product quality. High grain alpha-amylase can result from: preharvest sprouting (PHS)/germination when mature wheat is rained on before harvest, or from late maturity alpha-amylase (LMA) when grain experiences cool temperatures during the soft dough stage of grain maturation (Zadoks growth stage 85). An initial LMA-induction experiment found that low FN was associated with premature visible germination, suggesting that cool and humid conditions caused vivipary. To examine whether LMA and vivipary are related, controlled environment experiments examined the conditions that induce vivipary, whether LMA could be induced without vivipary, and whether the pattern of alpha-amylase expression during vivipary better resembled PHS or LMA. Vivipary was induced in the soft to hard dough stages of grain development (Zadok's stages 83-87) both on agar and after misting of the mother plant. This premature germination was associated with elevated alpha-amylase activity. Vivipary was more strongly induced under the cooler conditions used for LMA-induction (18°C day/7.5°C night) than warmer conditions (25°C day/18°C night). Cool temperatures could induce LMA with little or no visible germination when low humidity was maintained, and susceptibility to vivipary was not always associated with LMA susceptibility in a panel of 8 varieties. Mature grain preharvest sprouting results in much higher alpha-amylase levels at the embryo-end of the kernel. In contrast, vivipary resulted in a more even distribution of alpha-amylase that was reminiscent of LMA. Vivipary can occur in susceptible varieties under moist, cool conditions, and the resulting alpha-amylase activity may result in low FN problems when a farm experiences cool, rainy conditions before the crop is mature. While there are genotypic differences in LMA and vivipary susceptibility, overlapping mechanisms are likely involved since they are similarly controlled by temperature and growth stage, and result in similar patterns of alpha-amylase expression.

Antioxidant, starch-digesting enzymes inhibitory, and pasting properties of elite yellow-fleshed cassava genotypes

Biofortification of cassava roots has improved its health benefits by raising the quantity and bioavailability of bioactive compounds, particularly carotenoids. This study analyzed the bioactive constituents (carotenoids, tannins, total phenolics, and flavonoids), antioxidant, starch-digesting enzymes (α-amylase and α-glucosidase) inhibitory and pasting properties of flours of 18 elite yellow-fleshed cassava genotypes grown at the International Institute of Tropical Agriculture, Ibadan, using standard laboratory methods. Generally, the concentrations of the bioactive constituents (9-cis-β-carotene, 13-cis-β-carotene, all trans-β-carotene, total β-carotene, total carotenoids, tannins, total phenolics, and total flavonoids) of the different cassava genotypes varied. The antioxidant activity varied significantly among the different cassava genotypes, with IITA-TMS-IBA183001 having the highest reducing power (2.59 GAE mg/g) and most potent DPPH· scavenging ability (SC50: 14.56 mg/mL). However, the starch-hydrolysing enzymes (alpha-amylase and alpha-glucosidase) inhibitory and the pasting properties of the different genotypes were generally comparable. Total carotenoids content significantly correlated with the DPPH· SC50 (r = −0.495), while total phenolics content correlated with ABTS·+(r = 0.839) and DPPH· SC50 (r = −0.870). Also, tannins content significantly correlated with ABTS·+ (r = 0.553), while total flavonoids content was significantly correlated with α-amylase IC50 (r = −0.532). These findings suggest the potential of flours of the 18 elite yellow-fleshed cassava genotypes to serve as important dietary sources of antioxidants and starch-hydrolysing enzyme inhibitors, which may be beneficial in oxidative stress and postprandial hyperglycaemic conditions.

In vitro hypoglycemic and antioxidant activities of steamed Polygonatum cyrtonema Hua with various steaming degrees: Relationship with homoisoflavonoids

Polygonatum cyrtonema Hua, an edible and medicinal plant in China, is usually steamed and then dried before use. Changes in homoisoflavonoids composition, radical scavenging activity, starch digestive enzyme inhibitory activity, cell glucose consumption and intracellular ROS formation of steamed P. cyrtonema Hua rhizome with various steaming degrees were investigated. Nine homoisoflavonoids were identified in raw and steamed rhizome extracts, and their contents were almost increased with increasing steaming degree. Steamed rhizome extract had increased activities to scavenge free radicals, reduce ferric iron, and inhibit α-amylase and α-glucosidase. The treatment with dark-steamed and deep-dark-steamed rhizome extracts restored glucose consumption in IR-HepG2 cells to normal level, and suppressed ROS level to that of Trolox treated group. Multivariate analyses (heat-map, correlation coefficient and PCA) indicated that the hypoglycemic and antioxidant activities of steamed rhizome depended on steaming degree, and were significantly correlated with disporopsin and 5,7,2′,4′-tetrahydroxy-6-methyl-homoisoflavanone (p < 0.05). Overall, these results suggested that steaming degree had remarkable impacts on homoisoflavonoids composition and bioactivities of P. cyrtonema Hua rhizome, and homoisoflavonoids greatly contributed to these activities.

Purple red rice bran anthocyanins reduce the digestibility of rice starch by forming V-type inclusion complexes

Purple red rice bran, a by-product of the rice polishing process, contained abundant anthocyanins. However, most of them were discarded resulting in a waste of resources. This study investigated the effects of purple red rice bran anthocyanin extracts (PRRBAE) on the physicochemical properties and digestive properties of rice starch and its mechanism of action. Infrared spectroscopy and X-ray diffraction indicated that PRRBAE could interact with rice starch through non-covalent bonds to form intrahelical V-type complexes. The DPPH and ABTS+ assays showed that PRRBAE could confer better antioxidant activity on rice starch. In addition, the PRRBAE could increase the resistant starch content and decrease the enzyme activities by changing the tertiary and secondary structure of starch-digesting enzymes. Further, molecular docking suggested that aromatic amino acids play a key role in the interaction of starch-digesting enzymes with PRRBAE. These findings will contribute to a better understanding of the mechanism of PRRBAE reducing starch digestibility, and to the development of high value-added products and low glycemic index (GI) foods.

In vitro and in silico studies of silver nanoparticles (AgNPs) from Allium sativum against diabetes

In the present study, the silver nanoparticles (AgNPs) were synthesized from the bulbs of Allium sativum, characterized by UV–visible spectroscopy, FT-IR, SEM, HR-TEM, EDAX analysis and investigated its action on the inhibition of starch digestion. The results proved that the biosynthesized nanoparticles were uniformly dispersed, spherical shaped with the size ranging from 10 to 30 nm. The phytochemical and FT-IR analysis showed the presence of phenols, terpenoids, and amino acids in the synthesized AgNPs. The cytotoxicity analysis revealed that the synthesized AgNPs were non-toxic to the normal cells. The synthesized AgNPs exhibited significant free radical scavenging activity. The in vitro antidiabetic activity showed that the synthesized AgNPs increased glucose utilization, decreased hepatic glucose production, inhibited the activity of starch digestive enzymes such as α-amylase and α-glucosidase, and were not involved in the stimulation of pancreatic cells for the secretion of insulin. The in silico antidiabetic activity analysis (molecular docking) also revealed that the silver atoms of the AgNPs interacted with the amino acid residues of α-amylase, α-glucosidase, and insulin. The present study proved that the AgNPs synthesized from A. sativum have prominent antidiabetic activity in terms of reducing the hyperglycemia through the increased glucose utilization, decreased hepatic glucose production, and the inhibition of α-amylase and α-glucosidase enzymes. So it can be used as a promising nanomedicine for the treatment of diabetes.

Influence of traditional processing and genotypes on the antioxidant and antihyperglycaemic activities of yellow-fleshed cassava.

Yellow-fleshed cassava root (YFCR) is processed into traditional products that may influence its bioactivities. In this study, the antioxidant and anti-hyperglycaemic activities of three traditional products (lafun, fufu and gari) from five genotypes (IITA-TMS-IBA070337, 182961, 182962, 182986, 183044) of YFCR were evaluated. The YFCR genotypes were grown at the International Institute of Tropical Agriculture (IITA) research field, Ibadan. The bioactive constituents (total carotenoids, total phenolics, tannins and total flavonoids), antioxidant [2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation (ABTS•+) and 1,1-diphenyl-2- picrylhydrazyl radical (DPPH•) scavenging capacities, and reducing power], and starch-digesting enzymes (α-amylase and α-glucosidase) inhibitory activities of the products were determined using standard laboratory methods. The glucose response of the products was assessed in human subjects. The concentrations of the bioactive constituents of the products from different genotypes varied significantly (p < 0.05). The ABTS•+ and DPPH• scavenging capacities and the reducing power of the products also differed significantly (p < 0.05), such that the lafun from IITA-TMS-IBA182962, IITA-TMS-IBA070337 and IITA-TMS-IBA070337 had the strongest ABTS•+ and DPPH• scavenging capacities, and reducing power, respectively. The α-amylase and α-glucosidase inhibitory activities of the three products differed significantly (p < 0.05), with the lafun from IITA-TMS-IBA070337 and IITA-TMS-IBA07033 having the strongest α-amylase and α-glucosidase inhibitory activity, respectively. Also, the lafun from IITA-TMS-182986 had the least glucose response, while the fufu from IITA-TMS-IBA070337 had the highest glucose response. Overall, the lafun from different genotypes of YFCR had the most potent antioxidant and starch-digesting enzymes inhibitory activities and the least glucose responses. Hence, lafun may be a promising dietary intervention targeting oxidative stress, hyperglycaemia, and their resultant type 2 diabetes.

Milling of wheat bran: Influence on digestibility, hydrolysis and nutritional properties of bran protein during in vitro digestion

Wheat bran is a source of high-quality protein with low cost, but the accessibility of bran protein is notably limited by cell wall matrix. This study investigated the effect of milling on the distribution and profile of wheat bran protein, and explored its digestibility, hydrolysis and functional activity during in vitro digestion. It showed that superfine milling effectively released bran protein by disrupting aleurone cells and further improved its solubility and extractability. Superfine wheat bran (19 μm) had higher protein digestibility (53.1 %) and hydrolysis degree (12.7 %) compared to coarse wheat bran (84–1110 μm). Moreover, intestinal digestion promoted the release of free amino acid, mainly arginine (16.4 %), tyrosine (12.8 %) and phenylalanine (9.5 %). Superfine bran protein hydrolysate exhibited the highest antioxidant activity and starch-digestive enzyme inhibitory activity that could facilitate the application of bran as a multifunctional nutrient.

Physicochemical, antioxidant and starch-digesting enzymes inhibitory properties of pearl millet and sweet detar gluten-free flour blends, and sensory qualities of their breads

Natural sources of hydrocolloids may serve as healthier alternatives to modified hydrocolloids as gluten replacement in gluten-free food products. In this study, the physicochemical, antioxidant and starch-digesting enzymes inhibitory properties of gluten-free whole pearl millet flour (PMF) blended with 1.5% and 3% of either sweet detar flour (SDF, a natural source of hydrocolloids) or sodium carboxymethyl cellulose (SCMC, a modified hydrocolloid), and the sensory qualities of their breads were evaluated. White wheat flour (WWF) and its bread served as the control flour and bread, respectively. Amylose level and solubility index of the blends decreased, whereas their water absorption capacity, peak and final viscosity increased significantly as their proportions of SDF and SCMC increased. Total phenolics, tannins, and total flavonoids contents; DPPH•, ABTS•+ scavenging capacity, and reducing power; α-amylase and α-glucosidase inhibitory activities were significantly higher in PMF and its blends with SDF and SCMC than in the WWF. Further, the blend of PMF and 1.5% SDF had a stronger α-amylase and α-glucosidase inhibitory activity than those of PMF and SCMC (1.5 and 3%). Although the sensory qualities of the WWF bread were better than those of PMF and its blends with SDF and SCMC, the sensory qualities of PMF-SDF and PMF-SCMC breads were comparable. The study indicates that SDF could be a good substitute for SCMC in the development of PMF-based gluten-free bread, with an enhanced starch-digesting enzymes inhibitory property, targeting celiac disease and type 2 diabetes patients.

In vitro inhibition of starch digestive enzymes by ultrasound-assisted extracted polyphenols from Ascophyllum nodosum seaweeds.

Seaweeds are gaining importance due to their antidiabetic characteristics. This study investigated the inhibitory effects of aqueous Ascophyllum nodosum extracts, obtained by ultrasound‐assisted extraction with different sonication powers (70–90 W/cm2) and subjected to resin purification, against α‐amylase and α‐glucosidase enzymes. Different inhibition methodologies were carried out, preincubating the extract either with the enzyme or the substrate. Chemical characterization, in terms of proximate analysis, antioxidant capacity (2,2‐diphenyl‐1‐picryl‐hydrazyl‐hydrate [DPPH] and FRAP), and polyphenols characteristics (reversed‐phase high‐performance liquid chromatography [RP‐HPLC] and 1H‐NMR) were carried out to explain inhibitory activities of extracts. Sonication power did not influence the proximal composition nor antiradical activity of extracts, but increasing sonication power increased inhibition capacity (>15%) against both starch digestive enzymes. The extract purification largely improved the inhibition efficiency decreasing the IC50 of α‐amylase and α‐glucosidase by 3.0 and 6.1 times, respectively. Seaweed extracts showed greater inhibition effect when they were preincubated with the enzyme instead of the substrate. RP‐HPLC together with 1H‐NMR spectra allowed relating the presence of uronic acids–polyphenols complexes and quinones in the extracts with the different inhibitory capacities of samples.Practical ApplicationThe study confirms that ultrasound‐assisted extracts from Ascophyllum nodosum can be used to inhibit digestive enzymes. This opens the alternative to be used in foods for modulating glycemic index.