Effects of different fractions of polysaccharides from Dictyophora indusiata on high-fat diet-induced metabolic syndrome in mice.

Dictyophora indusiata is a common edible mushroom with great potential in the field of medicine against metabolic disorders, inflammation, and immunodeficiency. Our previous studies have shown that different fractions of the polysaccharide from Dictyophora indusiata (DIP) have various structural characteristics and morphology. However, the impact of the structural features on the protective effects of DIP against metabolic syndrome remains unclear. In this study, three distinct polysaccharide fractions have been extracted from Dictyophora indusiata and a high-fat diet-induced metabolic syndrome (MetS) was constructed in mice. The effects of these fractions on a range of MetS-associated endpoints, including abnormal blood glucose, lipid profiles, body fat content, liver function, intestinal microbiota and their metabolites were investigated. Through correlation analysis, the potential link between the monosaccharide composition of the polysaccharides and their biological activities was determined. The study aimed to explore the potential mechanisms and ameliorative effects of these polysaccharide fractions on MetS, thereby providing statistical evidence for understanding the relationship between monosaccharides composition of Dictyophora indusiata polysaccharides and their potential utility in treating metabolic disorders.

Validating the use of a newly developed cinnamaldehyde product in commercial broiler production.

Essential oils (EOs) have been considered as an alternative to antibiotics for animal production. In the current study, 4 trials were conducted on a commercial broiler farm to investigate the effects of dietary supplementation of an encapsulated cinnamon EO product (NE-OFF) on the bird growth performance, gut health, and gene expression in the ileum, spleen, and liver relating to the host response to heat and other stresses, including potential NE challenge. In each trial, approximately 30,000 Cobb or Ross broilers were randomly allocated to 4 treatments: a raised without antibiotics (RWA) commercial diet as positive control, an adjusted RWA commercial diet as negative control, and the negative control diet supplemented with 2 different dosages of NE-OFF, which was added during feed pelleting. Although the final average body weight did not differ significantly among treatment groups, birds fed NE-OFF had an increased ratio of villus height and crypt depth in the jejunum, and reduced fecal oocyst counts. Trial 2 was conducted in the summer and had a necrotic enteritis (NE) outbreak. The supplementation of NE-OFF reduced the NE incidence and bird mortality. The samples from Trial 2 were hence selected for the analyses of Clostridium perfringens and NetB toxin gene abundance in the ileum, and host responses. The C. perfringens population appeared to be positively correlated with the NetB gene abundance. The gene expression analysis suggested that NE-OFF supplementation improved nutrient absorption and transportation as well as antioxidant activities to help the birds against stress. These on-farm trial results support the hypothesis that the use of NE-OFF as a feed additive can improve bird gut health and performance in commercial broiler production, especially for preventing NE outbreaks when birds are under stress.

Glucans from Armillaria luteo-virens: Structural Characterization and In Vivo Immunomodulatory Investigation under Different Administration Routes.

Polysaccharides fromArmillaria luteo-virens (ALP) were investigated for structural characterization and immunomodulatory activities. Three fractions (ALP-1, ALP-2, and ALP-3) were obtained with the yield of 2.4, 3.7, and 3.0 wt %, respectively. ALP-1 was proposed as a ß-(1 → 3)(1 → 6)-glucan with a triple-helix conformation; ALP-2 and ALP-3 were both identified as α-(1 → 4)(1 → 6)-glucan differing in their Mw and branching degree with a spherical conformation. The in vitro digestibility experiment and in vivo experiments using cyclophosphamide (CY)-treated mice demonstrated that intraperitoneal injection of α-glucan (1 mg·kg-1·day-1) and intragastric gavage of ß-glucan (10 mg·kg-1·day-1) both effectively restored the decrease in body weight, immune organ indexes, immune cell activities, serum immune marker levels, colonic short-chain fatty acids (SCFA) levels, and Bacteroidetes/Firmicutes ratio in immunosuppression mice. This study provides novel insights into the immunomodulatory activity of α- and ß-glucans under different administration routes, thereby promoting their application in both food and pharmaceutical areas.

Unveiling the breadmaking transformation: Structural and functional insights into Arabinoxylan.

To understand the changes in arabinoxylan (AX) during breadmaking, multi-step enzyme digestion was conducted to re-extract arabinoxylan (AX-B) from AX-fortified bread. Their structural changes were compared using HPSEC, HPAEC, FT-IR, methylation analysis, and 1H NMR analysis; their properties changes in terms of enzymatic inhibition activities and in vitro fermentability against gut microbiota were also compared. Results showed that AX-B contained a higher portion of covalently linked protein while the molecular weight was reduced significantly after breadmaking process (from 677.1 kDa to 15.6 kDa); the structural complexity of AX-B in terms of the degree of branching was increased; the inhibition activity against α-amylase (76.81 % vs 73.89 % at 4 mg/mL) and α-glucosidase (64.43 % vs 58.08 % at 4 mg/mL) was improved; the AX-B group produced a higher short-chain fatty acids concentration than AX (54.68 ± 7.86 mmol/L vs 44.03 ± 4.10 mmol/L). This study provides novel knowledge regarding the structural and properties changes of arabinoxylan throughout breadmaking, which help to predict the health benefits of fibre-fortified bread and achieve precision nutrition.

Yellow mustard gum: pilot-scale production and characterization.

BACKGROUND: Yellow mustard gum (YMG), which is extracted from the mucilaginous part of yellow mustard bran, has been considered an emerging natural hydrocolloid gum but lacks commercial development and production. To promote the commercial utilization of YMG, this study developed a pilot-scale YMG production protocol in an economic and environmentally friendly way to produce a clean-label YMG product. This YMG produced at pilot scale (YMW) was characterized in terms of chemical composition, rheological properties, and interaction with a commercial gum, κ-carrageenan, and was compared with purified YMG through ethanol precipitation (YME). RESULTS: The protocol processed up to 100 L of raw material with zero solvent and a minimal number of steps and showed strong quasi-industrial potential. The YMW showed a similar chemical composition as YME. However, the YMW contained a slightly lower amount of carbohydrate and a much larger amount of ash and potassium than the YME. The rheological results concluded that both the YMW and YME solutions exhibited shear-thinning flow behavior and a weak gel, with YME showing higher viscosity and stronger gel structure. Most interestingly, YMW could form unpourable gels when blended with native κ-carrageenan whereas YME barely achieved this despite the equivalent total gum concentration. CONCLUSION: This study demonstrated the feasibility of YMG production at a large scale with economic and green procedures and discovered its new functionality for commercial utilization. The gelling ability of YMG could provide it with wider applications as a result of a new potential synergistic combination. All this information should accelerate the process of full commercialization of YMG as a clean-label functional ingredient. © 2024 His Majesty the King in Right of Canada. Journal of The Science of Food and Agriculture © 2024 Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

Intestinal organoids: A thriving and powerful tool for investigating dietary nutrients-intestinal homeostasis axis.

Dietary nutrients regulate intestinal homeostasis through a variety of complex mechanisms, to affect the host health. Nowadays, various models have been used to investigate the dietary nutrients-intestinal homeostasis axis. Different from the limited flux in animal experiments, limited intestinal cell types and distorted simulation of intestinal environment of 2D cells, intestinal organoid (IO) is a 3D culture system of mini-gut with various intestinal epithelial cells (IECs) and producibility of intestinal biology. Therefore, IOs is a powerful tool to evaluate dietary nutrients-intestinal homeostasis interaction. This review summarized the application of IOs in the investigation of mechanisms for macronutrients (carbohydrates, proteins and fats) and micronutrients (vitamins and minerals) affecting intestinal homeostasis directly or indirectly (polysaccharides-intestinal bacteria, proteins-amino acids). In addition, new perspectives of IOs in combination with advanced biological techniques and their applications in precise nutrition were proposed.

Innate immune receptors co-recognition of polysaccharides initiates multi-pathway synergistic immune response.

The law and mechanism of the interaction between polysaccharides and pattern recognition receptors (PRRs) has been unclear. Herein, three glucomannans with different structures were selected to explore the universal mechanism for PRRs to recognize glucomannans. Screening results showed that the silence of TLR4 but not TLR2 severely blocked the production of inflammatory cytokines and the transduction of signal pathways. In-depth results revealed that the participation of myeloid differentiation protein 2 (MD2) and CD14 and the dimerization of the TLR4-MD2 complex were required for glucomannan-activated TLR4 signal transduction. Mannose receptor (MR) was also engaged in glucomannan-induced respiratory burst, endocytosis, and inflammatory signaling pathways in a spleen tyrosine kinase-dependent manner. The internalization of glucomannans into the cytoplasm by MR directly initiated complex intracellular signaling cascades. Finally, molecular docking characterized the binding energy and binding sites between glucomannans and multiple receptors from other perspectives. The essence of glucomannans recognized by PRRs was the non-covalent interaction of multiple receptors and the subsequent transmission of the signal cascade was triggered in a multi-channel and cooperative manner. As a result, the hypothesis that "Innate immune receptors co-recognition of polysaccharides initiates multi-pathway synergistic immune response" was proposed to outline these meaningful phenomena.

Glucomannan from Aloe vera gel maintains intestinal barrier integrity via mitigating anoikis mediated by Nrf2-mitochondria axis.

Impairment of intestinal epithelium barrier is a hallmark of gut pathology. Cell death can compromise barrier function and impair epithelial restitution directly or indirectly in inflammatory bowel disease (IBD). Our previous work demonstrated that glucomannan from Aloe vera gel (AGP) protected mice from DSS-induced colitis, with unclear mechanism of AGP-intestinal barrier interactions. Here, AGP maintained the integrity of intestinal barrier in colitis mice. RNA-Sequencing results indicated that pathways related to anoikis (apoptosis induced by loss of cell-matrix interaction), mitochondrial function and oxidative stress were significantly altered in the process of AGP-intestinal barrier interaction. Further experiments confirmed that AGP activated Nrf2, decreased ROS levels, mitigated mitochondrial dysfunction and anoikis of colonic epithelial cells in mice. Intriguingly, AGP reversed oxidative stress and mitochondrial dysfunction induced by knockdown or inhibitor (ML385) of Nrf2 in IEC-6 cells, which indicated the essential role of Nrf2-mitochondrial axis in the intestinal protective function of AGP. In addition, AGP alleviated anoikis caused by impaired mitochondrial function. Hence, this current work indicated that AGP might maintain intestinal barrier integrity by mitigating anoikis mediated by Nrf2-mitochondria axis. These findings provide new evidence into the effect of polysaccharides maintaining intestinal barrier integrity.

Polysaccharides from natural Cordyceps sinensis attenuated dextran sodium sulfate-induced colitis in C57BL/6J mice.

As potential candidates for treating ulcerative colitis (UC), polysaccharides have been attracting extensive interest in recent years. Cordyceps sinensis (C. sinensis) is a kind of traditional Chinese edible food, and its polysaccharide fractions have been found to be effective in regulating immunity and protecting the kidneys. To determine the potential function of polysaccharides from natural C. sinensis on UC, their effects in terms of histological, serological, biochemical, and immunological aspects on dextran sulphate sodium (DSS)-induced colitis mice model were investigated. Results showed that the polysaccharides significantly alleviated colitis by increasing the colon length, alleviating colon tissue damage, and inhibiting the activation of the NF-κB pathway. In addition, polysaccharides reduced the contents of tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) in the serum, increased the number of goblet cells, and improved the expression of intestinal tight junction proteins (Occludin and Claudin-1). They also evidently enhanced the formation of IgA-secretory cells and sIgA contents. Furthermore, the polysaccharides modulated the gut microbiota by decreasing the relative abundance of Bilophila and increasing the relative abundance of Dehalobacterium, Coprococcus, Oscillospira, and Desulfovibrio, which is accompanied by an increase in the short chain fatty acids' (SCFAs) concentrations in cecal contents. These results suggested that C. sinensis polysaccharides possessed promising intervening effects on experimental acute UC in mice.

Fabrication, characterization, and lipid-lowering effects of naringenin-zein-sodium caseinate-galactosylated chitosan nanoparticles.

Naringenin is a natural flavonoid that is widely distributed in citrus fruits and pharmacologically demonstrated to licit lipid-lowering activity. However, the clinical relevance of naringenin is limited due to its poor water solubility and inefficient absorption. In this study, we designed and developed naringenin-zein-sodium caseinate-galactosylated chitosan nanoparticles (GC-NPs) for hepatocyte-specific targeting, with naringenin-zein-sodium caseinate-chitosan nanoparticles (CS-NPs) as a control. Electrostatic adsorption was the primary binding mode in the GC-NPs and CS-NPs. Moreover, the particle size and zeta potential of GC-NPs were larger than those of CS-NPs and both types of nanoparticles had similar encapsulation rates. In vitro study experiments demonstrated that GC-NPs aggregated inside and outside of the cell membrane and significantly inhibited total triglyceride and cholesterol levels in oleic acid-induced HepG2 cells (p < 0.05). In high-fat diet-fed C57BL/6J mice, GC-NPs administration visibly improved the body weight, total cholesterol, and triglyceride content in the serum and liver, and high-density lipoprotein cholesterol levels improved, which corresponded to liver histological results. Additionally, in vitro and in vivo assays demonstrated that GC-NPs exhibited higher lipid-lowering activity than CS-NPs and naringenin monomers. These results suggest that GC-NPs are effective for oral delivery of naringenin in lipid-lowering therapies.

Acetyl-glucomannan from Dendrobium officinale: Structural modification and immunomodulatory activities.

To understand the mechanisms of immunomodulatory effect, Dendrobium Officinale polysaccharides (DOP) were treated by ultrasound and mild base separately to generate fractions of various weight-average molecular weight (Mw) and degrees of acetylation (DA). The structural features, conformational properties, functional properties and immunomodulatory activities of original and modified DOPs were investigated. Ultrasonic treatment decreased the Mw and apparent viscosity and improved the water solubility of DOP. Mild base treatment remarkably reduced the DA and the water solubility, while the overall apparent viscosity was increased. Conformational analysis by triple-detector high performance size-exclusion chromatography showed that the molecular chain of DOP turned more compact coil conformation with decreased DA. Results from the macrophages RAW 264.7 analysis showed that samples sonicated for 200 min (Mw 34.2 kDa) showed the highest immune-regulation effects. However, the immunomodulatory effects of the samples after de-acetylation were all compromised compared to the original DOP. This study inspires further research to establish the structural-immunomodulatory relationships, which promote the application of DOP in both the food and medicine fields.

Application of yellow mustard mucilage and starch in nanoencapsulation of thymol and carvacrol by emulsion electrospray.

Starch/water soluble yellow mustard mucilage nanocapsules loaded with thymol and carvacrol (TC) were developed using electrospray atomization. Emulsions were electrosprayed, aiming to generate nanocapsules with a controlled release behavior of TC for antimicrobial packaging applications. To understand the effect of water soluble yellow mustard mucilage (WSM) on the nanocapsules, the emulsion viscosity, morphology, encapsulation efficiency, molecular interactions, and release kinetics were evaluated. Surface and internal morphological analysis revealed that nanocapsules were non-porous with minimal surface shrinkages and had inner multicore spheres within a solid wall layer. Encapsulation efficiency ranged from 61.17 to 84.10 %, increasing at higher TC contents. Fourier transform spectroscopy confirmed the molecular interaction between wall materials. The release kinetics of encapsulated TC (30 % w/w) followed a Fickian diffusion mechanism and a controlled release pattern up to 120 h. Results indicated that the addition of WSM can modulate the release kinetics of bioactives and achieve a controlled release pattern.

Comprehensive characterization of glucomannans from different sources to trigger moderate macrophages immune activation.

Macrophage activation is involved in the outcome of many diseases and is recognized as one of the best targets for disease intervention. Glucomannans had shown promising immunomodulatory potential. Herein, the activation performance of macrophages by glucomannans from different sources was thoroughly investigated. Glucomannans triggered the immune activation of macrophages, which was mainly manifested in increasing the secretion of immune effector molecules, enhancing the endocytosis and phagocytosis of macrophages, and selectively facilitating the expression of M1 phenotype. The participation of NF-κB and MAPK signaling pathways further validated the immune activation of macrophages by glucomannans. Correlation analysis indicated acetyl might be a feasible target for glucomannans to induce immune activation and the molecular weight (Mw) of glucomannans was also inseparable from the performance of immune activation. In conclusion, glucomannans showed a moderate immune activation effect on macrophages, and their difference in immune activation was closely related to the acetyl content and Mw.

Therapeutic potential of non-starch polysaccharides on type 2 diabetes: from hypoglycemic mechanism to clinical trials.

Non-starch polysaccharides (NSPs) have been reported to exert therapeutic potential on managing type 2 diabetes mellitus (T2DM). Various mechanisms have been proposed; however, several studies have not considered the correlations between the anti-T2DM activity of NSPs and their molecular structure. Moreover, the current understanding of the role of NSPs in T2DM treatment is mainly based on in vitro and in vivo data, and more human clinical trials are required to verify the actual efficacy in treating T2DM. The related anti-T2DM mechanisms of NSPs, including regulating insulin action, promoting glucose metabolism and regulating postprandial blood glucose level, anti-inflammatory and regulating gut microbiota (GM), are reviewed. The structure-function relationships are summarized, and the relationships between NSPs structure and anti-T2DM activity from clinical trials are highlighted. The development of anti-T2DM medication or dietary supplements of NSPs could be promoted with an in-depth understanding of the multiple regulatory effects in the treatment/intervention of T2DM.

Conformational Properties of Flaxseed Rhamnogalacturonan-I and Correlation between Primary Structure and Conformation.

The pectic polysaccharides extracted from flaxseed (Linum usitatissiumum L.) mucilage and kernel were characterized as rhamnogalacturonan-I (RG-I). In this study, the conformational characteristics of RG-I fractions from flaxseed mucilage and kernel were investigated, using a Brookhaven multi-angle light scattering instrument (batch mode) and a high-performance size exclusion chromatography (HPSEC) system coupled with Viscotek tetra-detectors (flow mode). The Mw of flaxseed mucilage RG-I (FM-R) was 285 kDa, and the structure-sensitive parameter (ρ) value of FM-R was calculated as 1.3, suggesting that the FM-R molecule had a star-like conformation. The Mw of flaxseed kernel RG-I (FK-R) was 550 kDa, and the structure-sensitive parameter (ρ) values ranged from 0.90 to 1.21, suggesting a sphere to star-like conformation with relatively higher segment density. The correlation between the primary structure and conformation of RG-I was further discussed to better understand the structure-function relationship, which helps the scale-up applications of pectins in food, pharmaceutical, or cosmetic industries.

Loadings of lycopene in emulsion and sodium alginate-K-carrageenan composite systems: Preparation, characterization, bioaccessibility, and kinetics.

This research aims to prepare capsules emulsion using gallic acid (GA), dextran (DEX), bovine serum albumin (BSA), sodium alginate, and K-carrageenan (K-Car) as the biological delivery system of lycopene. The stability and bioaccessibility of lycopene were further improved through encapsulation of covalent complex of sodium alginate and K-Car. The molecular weight distribution and secondary structure of the conjugates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR). The storage stability of the emulsion stabilized by conjugates was measured with Turbiscan stability index (TSI) and fluctuation of the particle size. The TSI value of ternary conjugates was 18.7 (37℃) with particle sizes ranging from 208 to 319 nm. Then, the changes of three-dimensional reticulate structures and physical properties of sodium alginate-K were analyzed by scanning electron microscopy (SEM) and TPA. The thermal stability of the sodium alginate-K-Car composite systems was increased compared with sodium alginate. The bioaccessibility of lycopene was significantly improved under the dual embedding of BSA-DEX-GA conjugate emulsion and sodium alginate-K-Car composite systems.

Impact of pectin with various esterification degrees on the profiles of gut microbiota and serum metabolites.

Colitis is generally affected by multiple factors, including the dysbiosis of intestinal microbiota, and may affect organs outside colon through circulation. Pectin, which is an edible polysaccharide widely present in plant cell walls, has been proved in our previous study to possess preventive potentials against acute ulcerative colitis, especially when the esterification degree is less than 50%. This study aimed to clarify the underlying correlations of gut microbiome and serum metabolites with the preventive effects of pectin with different esterification degrees (H121, L13, and L102) against colitis in mice. MiSeq sequencing data showed that symbiotic bacteria especially beneficial Lactobacillus and Bifidobacterium were enriched by pectin intake. Fiber consumers such as Prevotella and Bacteroides actively responded to L13 pectin, particularly under high dosage (L13-H). In addition, the abnormal abundance of Akkermansia associated with colitis would not appear in mice who had been provided with any of the three pectins before dextran sulfate sodium (DSS) treatment. Furthermore, pre-treatment of H121 and L13 pectins could improve the serum glycerophospholipids such as phosphatidylcholine (PC) and phosphatidylethanolamine (PE). In contrast, lysophosphatidic acid (LPA) contributing to the glycerophospholipid metabolism pathway was enriched only in the L13-H group, which has been previously proved to be associated with the epithelial barrier and intestinal homeostasis. Positive relationships between the glycerophospholipids and the dominant candidates of intestinal bacteria such as Lactobacillus indicated the joint actions of intestinal microbes and serum metabolites as well as the underlying crosstalks among gut microbiome. Therefore, the results of this research suggested that the preventive effects of low-esterified pectin on DSS-induced colitis were likely to be initiated by the enrichment of probiotics in the gut and serum glycerophospholipids. KEY POINTS: • L13 pectin remarkably improved the diversity of the gut microbiome in healthy mice. • Probiotics were enriched and abnormal Akkermansia was restored by L13 and L102 pectins. • Glycerophospholipid metabolism was significantly enriched by H121 and L13 pectins.

Different thermal treatments of highland barley kernel affect its flour physicochemical properties by structural modification of starch and protein.

Highland barley (HB) has become popular due to nutritional benefits, and thermal treatment could broaden its application. In this study, superheated steam (SS) as a novel commercially thermal treatment was compared with other traditional heating (steam and roasting). The physiochemical properties of treated HB kernels and subsequent produced flour were investigated. After thermal treatments, gelatinization enthalpy was decreased by 38.39% and the degree of gelatinization was increased by 38.40%. SS at 180 °C (SS-180) induced the highest thermal stability, lowest viscoelasticity gel and delayed the starch retrogradation compared to other treatments. Meanwhile, SS-180 caused lowest short-range order and relative crystallinity of starch along with changes in protein secondary structure. Particularly, SS-180 decreased damaged starch content by 6.44% due to starch granules closely wrapped by glue-like protein, while steam and roasting increased it by 32.92% and 21.40%, respectively. Overall, SS treatment is most effective to improve the physiochemical properties of HB.

Purple sweet potato anthocyanin extract regulates redox state related to gut microbiota homeostasis in obese mice.

This study explored the advantageous effects of purple sweet potato anthocyanin extract (PSPAE) on redox state in obese mice. The normal chow diet (NCD) group, high-fat/cholesterol diet (HCD) group, and three groups based on HCD and added with low, middle, and high dose of PSPAE (PAL, PAM, and PAH) were raised for 12 weeks. High dose of PSPAE treatment decreased the elevations of the body weight by 24.7%, serum total cholesterol by 48.3%, serum triglyceride by 42.4%, and elevated serum activities of glutathione peroxidase by 53.3%, superoxide dismutase by 57.8%, catalase by 75.4%, decreased serum contents of malondialdehyde by 27.1% and lipopolysaccharides by 40.5%, as well as increased caecal total short-chain fatty acid by 2.05-fold. Additionally, PSPAE depressed toll-like receptor 4 (TLR-4), nuclear factor kappa-B (NF-κB), interleukin 6, tumor necrosis factor α, and preserved nuclear factor erythroid-2-related factor 2 (Nrf2) gene expression. Similarly, the protein expression of Nrf2 was enhanced, while TLR-4 and p-NF-κB/NF-κB were depressed by PSPAE treatment. Moreover, PSPAE administration promoted the protection of intestinal barrier function and rebuilt gut microbiota homeostasis by blooming g_Akkermansia, g_Bifidobacterium, and g_Lactobacillus. Furthermore, antibiotic interference experiments showed that the gut microbiota was indispensable for preserving the redox state of PSPAE. These results suggested that PSPAE administration could be an opportunity for improving HCD-induced obesity and the redox state related to gut dysbiosis. PRACTICAL APPLICATION: Purple sweet potato anthocyanin has diverse pharmacological properties. It is applicable for individuals to consume extracts (as pills or other forms) from raw purple sweet potato if they want to improve obesity or redox state.

Comparison of quercetin and rutin inhibitory influence on Tartary buckwheat starch digestion in vitro and their differences in binding sites with the digestive enzyme.

Inhibitory effects of flavonoids on starch digestibility were well known, but the structural mechanism was not clear. This study was focused on the diverse effect of quercetin and rutin on digestibility of Tartary buckwheat starch. Results showed that quercetin and rutin reduced the starch digestion by altering starch structure in bound forms and inhibiting digestive enzyme activity in free forms simultaneously, and quercetin showed a stronger effect than rutin. Molecular docking and saturation transfer difference-nuclear magnetic resonance (STD-NMR) revealed different binding site of rutin from quercetin was due to its hydroxyl and hydrogen on the glycoside structure. Rutin interacted with enzymes mainly by CH and OH on the glycoside structure which induced steric hindrance and restricted the inhibitory effect of quercetin fraction. The glycoside structure weakened inhibition of rutin on digestive enzymes in free forms rather than influence its anti-digestive effects in bound forms with starch.