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Even though starch seems a simple carbohydrate, composed only of glucose connected by two types of linkages, it has an amazing complexity related to its branched structure and extremely large size. Today, there are still unanswered questions that present challenges to the starch research field. Even though advances have been made in correlating starch amylopectin and amylose fine structural feature to functional properties, such as texture or digestibility, the form of the internal architecture of amylopectin is still not agreed upon. The future holds challenges in further resolving structure-function relationships of starch, and to understand and implement ways to improve the healthiness of starchy foods.

Three different storage temperatures including room temperature (RT), 4 °C and −20 °C were investigated in this study, with respects to their effects on the retrogradation property and in vitro digestibility of gelatinized sago starch. Storage at −20 °C resulted in the highest amount of both intra- and intermolecular double helices and a fracture-like structure under scanning electron microscopy (SEM). These crystallites were more homogenous while less thermally stable than that from RT and 4 °C storage conditions. Storage at RT significantly increased the stability and heterogeneity of the formed crystallites, resulting in a sponge-like structure under SEM. Causally, the digestion rate of retrograded sago starch by α-amylase was significantly lowered after storage at −20 °C compared to that at RT and 4 °C. The crystallite heterogeneity, thermal stability, and ratio of inter- to intramolecular double helices were possibly the main driven factors for the observed digestion rates instead of the amount and micro-morphology of the crystallites. These results supply potential tools for the manufacture of food products with slower starch digestibility.

Food-to-food fortification (FtFF) with moringa leaf (iron source) and/or baobab fruit (citric acid and ascorbic acid source) (each 13-15 g/100 g porridge dry basis (db)) was studied to improve iron and zinc nutritive quality in African-type wholegrain maize-based porridges using

The structure-function relationships of plant-based proteins that give rise to desirable texture attributes in order to mimic meat products are generally unknown. In particular, it is not clear how to engineer viscoelasticity to impart cohesiveness and proper mouthfeel; however, it is known that intermolecular β-sheet structures have the potential to enhance the viscoelastic property. Here, we investigated the propensity of selected peptide segments within common corn α-zein variants to maintain stable aggregates and β-sheet structures. Simulations on dimer systems showed that stability was influenced by the initial orientation and the presence of contiguous small hydrophobic residues. Simulations using eight-peptide β-sheet oligomers revealed that peptide sequences without proline had higher levels of β-sheet structuring. Additionally, we identified that sequences with a dimer hydrogen-bonding density of >22% tended to have a larger percent β-sheet conformation. These results contribute to understanding how the viscoelasticity of zein can be increased for use in plant-based meat analogues.

A new synthetic methodology has been developed for the synthesis of sulfinate alkyl and aryl esters. The methodology involves the combination of p-toluenesulfinic acid and 1,1′-carbonyldiimidazole (CDI) to create the putative reagent sulfinylimidazole. The process spontaneously releases carbon dioxide upon the addition of the CDI to the acid suggesting the rapid formation of the proposed reagent. Reaction of this reagent with a series of alcohols (primary, secondary, and tertiary) afforded the corresponding sulfinate alkyl esters in good to excellent yields by the addition of alcohols. It was also possible to form the related sulfinate aryl esters by treating the proposed sulfinylimidazole with selected phenols (phenol, p-tert-butylphenol, and thymol). The aryl esters were formed in excellent conversion based on analysis of the 500 MHz 1H NMR spectra of the crude reaction mixtures.

As the prevalence of obesity and diabetes has continued to increase rapidly in recent years, dietary approaches to regulating glucose homeostasis have gained more attention. Starch is the major source of glucose in the human diet and can have diverse effects, depending on its rate and extent of digestion in the small intestine, on postprandial glycemic response, which over time is associated with blood glucose abnormalities, insulin sensitivity, and even appetitive response and food intake. The classification of starch bioavailability into rapidly digestible starch, slowly digestible starch, and resistant starch highlights the nutritional values of different starches. As starch is the main structure-building macroconstituent of foods, its bioavailability can be manipulated by selection of food matrices with varying degrees of susceptibility to amylolysis and food processing to retain or develop new matrices. In this review, the food factors that may modulate starch bioavailability, with a focus on food matrices, are assessed for a better understanding of their potential contribution to human health. Aspects affecting starch nutritional properties as well as production strategies for healthy foods are also reviewed, e.g., starch characteristics (different type, structure, and modification), food physical properties (food form, viscosity, and integrity), food matrix interactions (lipid, protein, nonstarch polysaccharide, phytochemicals, organic acid, and enzyme inhibitor), and food processing (milling, cooking, and storage).

Leishmaniasis, a parasitic infectious disease transmitted by sandfly bites, is an extremely complex human and veterinary disease. In humans, it takes different forms ranging from self-healing cutaneous ulcers to severe, life-threatening visceral infections. Current treatments primarily rely on chemotherapies. The current chemotherapeutic drugs, developed decades ago, are costly, toxic, and have become problematic due to drug resistance. To this end, two naphthalene sulfonamides and one naphthalene sulfonate ester were subjected to a structure–activity relationship (SAR) study for inhibition of Leishmania. The new chlorosulfonamide, N-(2′-chlorophenyl)-1-naphthalene sulfonamide (B), and sulfonate ester, 3-methyl-4-((naphthalen-1-ylsulfonyl)oxy)benzoic acid achieved (C) IC50 values of 9.5 μM and 7.4 μM, respectively, against Leishmania tarentolae promastigotes in vitro, which are notably lower than the IC50 value of 49 μM for our benchmark compound, N-(4′-carboxy-2′-methylphenyl)-1-napthalenesulfonamide (A). Additionally, all three compounds were analyzed by X-ray crystallography and show strong intermolecular interactions in the crystalline state. The new findings from this SAR study open new directions for advanced leishmaniasis treatment.

The impact of the internal part of aewx amylopectin on the gel network and digestibility during retrogradation was investigated using wx amylopectin as a reference. After β-amylolysis for 60 min (aewx-60), greater shifts in both λmax value and absorbance of iodine binding profiles were observed, accompanied by an increment of short chains (DP 3–5) with reducing the external long chains (DP 17.2). For the amylopectin gels aged 7 days at 4 °C, aewx had greater intermolecular aggregation of double helices to form junction zones, resulting in remarkably higher G′, which was significantly greater than that of wx amylopectin or aewx-60. Moreover, aewx amylopectin had a greater RS accompanied by a reduction in RDS after retrogradation. The gel network models of retrograded amylopectins were built to interpret more molecular interactions for aewx than those of wx. The results revealed that aewx amylopectin with a higher proportion of longer external chains prompted the flexibility to align and interact for the formation of double helices and enzyme-resistant structures.

Amide I and Amide III vibrational modes are frequently used to study protein secondary structure with Fourier transform infrared (FT-IR) spectroscopy. However, for protein mixtures, neither the sole Amide I nor Amide III region provides sufficient information for structural quantitation because of overlapping peaks, especially in the Amide I region. Here, an improved quantitative approach is proposed to estimate secondary structure of protein systems using resolution enhancement and curve-fitting data processing techniques on a gluten model system to investigate structure-function relationships. Twelve different scenarios were prepared to assign bands in the Amide I region. Frequency ranges of 1660–1640 cm−1 and 1665–1660 cm−1 were found to highly contribute to variability in secondary structure contents of samples. Utilization of the Amide III region as a conducive tool to assign bands in the Amide I region led to a better differentiation of some secondary structural motifs and a more accurate quantitation of protein secondary structure. The study presents an understanding of FT-IR data analysis for a quick technique to assess secondary structures of protein mixtures.

Alzheimer’s Disease (AD) is a devastating neurodegenerative disorder where one of the commonly observed pathological hallmarks is extracellular deposits of the peptide amyloid-β (Aβ). These deposits contain a high concentration of metals and initially presented a promising target for therapy; however it has become increasingly evident that the soluble form of the peptide is neurotoxic, not the amyloidogenic species. Metal-based therapeutics are uniquely suited to target soluble Aβ and have shown considerable promise to prevent the aggregation and induced cytotoxicity of the peptide in vitro. Herein, we have prepared a small series of derivatives of two promising Ru(iii) complexes NAMI-A (imidazolium [trans-RuCl4(1H-imidazole)(dimethyl sulfoxide-S)]) and PMRU20 (2-aminothiazolium [trans-RuCl4(2-aminothiazole)2]), to determine structure–activity relationships (SAR) for Ru(iii) therapeutics for AD. Using the three complementary methods of Thioflavin T fluorescence, dynamic light scattering (DLS), and transmission electron microscopy (TEM), it was determined that the symmetry around the metal center did not significantly impact the activity of the complexes, but rather the attached thiazole ligand(s) mitigated Aβ aggregation. Across both families of Ru(iii) complexes the determined SAR for the functional groups on the thiazole ligands to modulate Aβ aggregation were NH2 > CH3 > H. These results highlight the importance of secondary interactions between the metallotherapeutic and the Aβ peptide where hydrogen-bonding has the greatest impact on modulating Aβ aggregation.

The glycemic carbohydrates we consume are currently viewed in an unfavorable light in both the consumer and medical research worlds. In significant part, these carbohydrates, mainly starch and sucrose, are looked upon negatively due to their rapid and abrupt glucose delivery to the body which causes a high glycemic response. However, dietary carbohydrates which are digested and release glucose in a slow manner are recognized as providing health benefits. Slow digestion of glycemic carbohydrates can be caused by several factors, including food matrix effect which impedes α-amylase access to substrate, or partial inhibition by plant secondary metabolites such as phenolic compounds. Differences in digestion rate of these carbohydrates may also be due to their specific structures (e.g. variations in degree of branching and/or glycosidic linkages present). In recent years, much has been learned about the synthesis and digestion kinetics of novel α-glucans (i.e. small oligosaccharides or larger polysaccharides based on glucose units linked in different positions by α-bonds). It is the synthesis and digestion of such structures that is the subject of this review.

An accurate high-performance anion-exchange chromatography (HPAEC) method is presented to measure the inhibition property of flavonoids against mammalian starch digestive enzymes, because flavonoids interfere with commonly used 3,5-dinitrosalicylic acid (DNS) and glucose oxidase/peroxidase (GOPOD) methods. Eriodictyol, luteolin, and quercetin increased absorbance values (without substrate) in the DNS assay and, with substrate, either overestimated or underestimated values in the DNS and GOPOD assays. Using a direct HPAEC measurement method, flavonoids showed different inhibition properties against α-amylase and α-glucosidases, showing different inhibition constants (Ki) and mechanisms. The double bond between C2 and C3 on the C-ring of flavonoids appeared particularly important to inhibit α-amylase, while the hydroxyl group (OH) at C3 of the C-ring was related to inhibition of α-glucosidases. This study shows that direct measurement of starch digestion products by HPAEC should be used in inhibition studies, and provides insights into structure-function aspects of polyphenols in controlling starch digestion rate.

Here, we reveal a new food gel formed on simple pH reduction of a water-soluble crosslinked corn bran arabinoxylan complex. This is different from low pH gelling high-methoxyl pectin that requires high sugar content, and it is similar in gelling property to low acyl gellan gum though is readily soluble in water. Alkaline-solubilized corn bran arabinoxylan (CAX) with two levels of residual bound ferulic acid was treated with laccase, a crosslinking enzyme, to produce two soluble, crosslinked CAX (SCCAX) complexes of different sizes (avg. 3.5 and 4.5-mer). Both of the SCCAXs formed gels at pH 2, with the larger, more heavily feruloylated SCCAX forming the stronger gel. Gels showed shear-thinning behavior and a thermal and pH reversible property. A gel forming mechanism was proposed to occur through noncovalent crosslinking including hydrogen bonds and hydrophobic interaction among the SCCAX complexes. This mechanism was supported by structural characterization of crosslinked CAX complexes using a Zeta-sizer and FT-IR spectroscopy. Applications of SCCAX gels might be where low pH low sugar gels are desired or a beverage containing SCCAX might be taken with gelling occurring in the low pH environment of the stomach, as well as in other food gels and as a drug delivery matrix.

Mucosal α-glucosidases from rat intestinal powder were employed, with a step to remove α-amylase, to measure the possibility of different inhibition of catechins, particularly those found in tea, on the four α-glucosidase enzymes. Inhibition of catechins was investigated for the slowing of digestion of glycemic carbohydrates, thus regulating glucose release and absorption. The α-glucosidases were fractionated using size-exclusion chromatography. The partially purified fractions showed higher α-glucosidase activity without any α-amylase activity. Catechins had selective inhibition properties on the α-glucosidases. In particular, (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) showed comparably high inhibitory effect on all four individual α-glucosidases, while (-)-epicatechin (EC), and (+)-catechin (C) indicated a more discriminating effect with relatively higher inhibitory effects on sucrase-isomaltase. The findings suggest that catechins differently inhibit the individual subunits of the α-glucosidases, and that they could modulate postprandial blood glucose levels through slowing digestion rate of starch and other glycemic carbohydrates, including sucrose.

Potatoes are rich in phenolic compounds which have been reported to impact starch digestion and intestinal glucose transport in model systems through phenolic-starch interactions. While these effects are well documented for pigmented potatoes and in model systems, the relevance of phenolics to the glycemic properties of processed colorless potato-based foods under naturalistic conditions remains unclear. This study assessed impacts of processing on phenolic concentrations, resistant starch content and glycemic properties of Russet Burbank and Shepody potatoes. Product forms included French fries, shredded (hash browns) and diced (home fries) produced through commercial processing as well as parallel in-home techniques. Commercial products had significantly higher concentrations of resistant starch (p < 0.05, 1.48-6.57 vs. 1.23-2.22 g per 100 fresh weight) and resistant starch/total starch ratio (5.42-18.3% vs. 3.58-7.62%) compared to freshly prepared counterparts, while statistically lower total caffeoylquinic acid content (2.94-10.9 vs. 11.5-25.2 g per 100 fresh weight). Glucose release and intestinal transport assessed using an in vitro digestion/Caco-2 cell monolayers model demonstrated a reduction in d7-glucose intestinal transport from commercially processed products relative to fresh prepared counterparts (p < 0.05, 31.3-61.2% vs. 79.3-110% at 60 min). Commercial Russet Burbank potato products including French fries, home fries and hash browns were then selected for clinical assessment of glycemic response and appetite rating by 23 participants (11 male and 12 female). The three products presented a subtle but discernable ascending trend (French fry ≥ home fry ≥ hash browns) for incremental area under the curve (IAUC, 95.2 ± 12 vs. 105 ± 10 vs. 107 ± 14 mM min, p < 0.05) at 2 h post breakfast and for appetite rating (45.2 ± 6.3 vs. 52.4 ± 4.1 vs. 57.7 ± 7.2 for hunger) at 4 h post breakfast with no significant difference from the control (whole wheat pancake). These results suggest that potato phenolics have only a modest influence on acute glycemic responses.

An unusual shear-thickening behavior was observed in 10% w/w gelatinized waxy potato and waxy corn starch dispersions at shear rates around 20 s−1. However, the phenomenon was not found in gelatinized dispersions of waxy rice. The aim of this study was to investigate reasons for the observed shear-thickening behavior as well as its relationship with the amylopectin molecular structure. This unique phenomenon only appears at a shear rate of about 20 s−1 during the increasing shear rate stage of the first cycle of a two-cycle steady shear flow test. After 7 d storage, the shear-thickening behavior of waxy potato starch dispersions disappeared, while it remained in waxy corn starch dispersions. A small strain temperature sweep test applied to waxy potato starch dispersions stored for 7 d showed a significant increase in the elastic behavior of dispersions at temperatures lower than 60 °C. This behavior was not observed on fresh and 7 d stored waxy corn and waxy rice dispersions. The study provides valuable information on a unique rheological behavior of waxy starch dispersions and its relationship to the amylopectin structure, thus opening opportunities for the design of novel foods with desired nutritional and textural properties.

In this study, a glucanotransferase from prokaryotic Azotobacter chroococcum NCIMB 8003 was recombinantly expressed and its biochemical characteristics and bioconversion ability for starch were investigated. The purified enzyme has the optimum activity at 55 °C and pH 6.5-7.0, as well as a melting temperature of 62 °C. The double-charged ion Ca2+ stimulated the activity of the enzyme by approximately 2.4 times. The kinetic parameters and specificity analysis revealed that this glucanotransferase had a higher affinity for high-amylose starch. During the transglycosylation reaction, the starch molecule was converted into a relatively small polymer with a narrow size distribution. For the enzyme modification of high-amylose starch for 72 h, the amount of α-1,6 linkages increased from 1.9% to 22.7% and the content of resistant starch (RS) increased from 3.18% to 17.83%. In addition, the fine structure displayed the reuteran-like highly branched glucan linked by single linear α-1,6 linkages and α-1,4/6 branching points. These results revealed that a promising prebiotic dietary fiber was synthesized from starch with glucanotransferase modification.

Nowadays, carbohydrate-based foods have a negative consumer connotation and low carb diets have become a popular way to lose weight. Here, we show how digestible starch and flavonoids can be used as a dietary approach to manage food intake and weight gain through elevation of glucagon-like peptide-1 (GLP-1) secretion for gut-brain axis communication. This was achieved by extending the digestion of cooked starch to the distal small intestine using luteolin or quercetin as α-amylase-specific inhibitors with competitive inhibition mechanism. In a mouse model, extended and complete digestion produced a signature blunted glycemic profile that induced elevation of GLP-1 and positive regulation of hypothalamic neuropeptides with significantly reduced food intake and weight gain (p 0.05). These findings represent a shift in paradigm of dietary carbohydrates from weight increasing to reducing, and have implications for industry and public health related to the design of carbohydrate-based foods/ingredients for managing obesity and diabetes.

In the present study, 14 structurally unique flavonoids were screened to systematically investigate structural requirements for selectively inhibiting human α-amylase versus α-glucosidase to obtain a slow but complete starch digestion for health benefit. The selective inhibition property of three flavonoids chosen against the two classes of starch digestive enzymes was confirmed through various analytical techniques - in vitro inhibition assay, fluorescence quenching, kinetic study, and molecular modeling. Considering the chemical structure of flavonoids, the double bond between C2 and C3 and OH groups at A5 and B3 are critical for the inhibition of α-amylase allowing flavonoids to lie parallel on the α-amylase catalytic active site, whereas the OH groups at B3 and C3 are important for α-glucosidase inhibition causing B-ring specific entry into the catalytic active site of α-glucosidase. Our findings provide insights into how to apply flavonoids to effectively control digestion rate for improving physiological responses.

A new synthetic methodology has been developed for the synthesis of N-alkyl and N-aryl arenesulfinamides. The methodology involved reacting arenesulfinic acids (R = -Me, -H, -Cl) with 1,1���-carbonyldiimidazole (CDI) to form the reactive intermediate, an arenesulfinylimidazole. This intermediate was then reacted with both primary and secondary amines to yield the corresponding N-alkyl sulfinamides in yields up to 90%. While the overall yields ranged from 52% to 90%, the level of diastereoselection with racemic or enantiomerically enriched amines only reached a level of 54:46 favoring the major diastereomer as determined by analysis of the 500 MHz 1H NMR spectra. A series of aniline derivatives were also investigated as coupling partners and were found to form the N-aryl arenesulfinamide in good yield.

While gut bacteria have different abilities to utilize dietary fibers, the degree of fiber structural alignment to bacteria species is not well understood. Corn bran arabinoxylan (CAX) was used to investigate how minor polymer fine structural differences at the genotype × environment level influences the human gut microbiota. CAXs were extracted from 4 corn genotypes × 3 growing years and used in in vitro fecal fermentations. CAXs from different genotypes had varied contents of arabinose/xylose ratio (0.46−0.54), galactose (58−101 mg/g), glucuronic acid (18−32 mg/g). There was genotype- but not environment-specific differences in fine structures. After 24 h fermentation, CAX showed different acetate (71−86 mM), propionate (35−44 mM), butyrate (7−10 mM), and total short chain fatty acid (SCFA) (117−137 mM) production. SCFA profiles and gut microbiota both shifted in a genotype-specific way. In conclusion, the study reveals a very high specificity of fiber structure to gut bacteria use and SCFA production.

Differences in the chemical and physical properties of dietary fibers are increasingly known to exert effects on their fermentation by gut microbiota. Here, we demonstrate that maize bran particle size fractions show metabolic output and microbial community differences similar to those we previously observed for wheat brans. As for wheat brans, maize bran particles varied in starch and protein content and in sugar composition with respect to size. We fermented maize bran particles varying in size in vitro with human fecal microbiota as inocula, measuring their metabolic fate [i.e., short-chain fatty acids (SCFAs)] and resulting community structure (via 16S rRNA gene amplicon sequencing). Metabolically, acetate, propionate and butyrate productions were size-dependent. 16S rRNA sequencing revealed that the size-dependent SCFA production was linked to divergent microbial community structures, which exerted effects at fine taxonomic resolution (the genus and species level). These results further suggest that the physical properties of bran particles, such as size, are important variables governing microbial community compositional and metabolic responses.

Previously, we have identified and characterized 4,6-α-glucanotransferase enzymes of the glycosyl hydrolase (GH) family 70 (GH70) that cleave (α1→4)-linkages in amylose and introduce (α1→6)-linkages in linear chains. The 4,6-α-glucanotransferase of Lactobacillus reuteri 121, for instance, converts amylose into an isomalto/malto-polysaccharide (IMMP) with 90% (α1→6)-linkages. Over the years, also, branching sucrase enzymes belonging to GH70 have been characterized. These enzymes use sucrose as a donor substrate to glucosylate dextran as an acceptor substrate, introducing single -(1→2,6)-α-d-Glcp-(1→6)- (Leuconostoc citreum enzyme) or -(1→3,6)-α-d-Glcp-(1→6)-branches (Leuconostoc citreum, Leuconostoc fallax, Lactobacillus kunkeei enzymes). In this work, we observed that the catalytic domain 2 of the L. kunkeei branching sucrase used not only dextran but also IMMP as the acceptor substrate, introducing -(1→3,6)-α-d-Glcp-(1→6)-branches. The products obtained have been structurally characterized in detail, revealing the addition of single (α1→3)-linked glucose units to IMMP (resulting in a comb-like structure). The in vitro digestibility of the various α-glucans was estimated with the glucose generation rate (GGR) assay that uses rat intestinal acetone powder to simulate the digestive enzymes in the upper intestine. Raw wheat starch is known to be a slowly digestible carbohydrate in mammals and was used as a benchmark control. Compared to raw wheat starch, IMMP and dextran showed reduced digestibility, with partially digestible and indigestible portions. Interestingly, the digestibility of the branching sucrase modified IMMP and dextran products considerably decreased with increasing percentages of (α1→3)-linkages present. The treatment of amylose with 4,6-α-glucanotransferase and branching sucrase/sucrose thus allowed for the synthesis of amylose/starch derived α-glucans with markedly reduced digestibility. These starch derived α-glucans may find applications in the food industry.

Diet, especially with respect to consumption of dietary fibers, is well recognized as one of the most important factors shaping the colonic microbiota composition. Accordingly, many studies have been conducted to explore dietary fiber types that could predictably manipulate the colonic microbiota for improved health. However, the majority of these studies underappreciate the vastness of fiber structures in terms of their microbial utilization and omit detailed carbohydrate structural analysis. In some cases, this causes conflicting results to arise between studies using (theoretically) the same fibers. In this investigation, by performing in vitro fecal fermentation studies using bran arabinoxylans obtained from different classes of wheat, we showed that even subtle changes in the structure of a dietary fiber result in divergent microbial communities and metabolic outputs. This underscores the need for much higher structural resolution in studies investigating interactions of dietary fibers with gut microbiota, both in vitro and in vivo., The chemical structures of soluble fiber carbohydrates vary from source to source due to numerous possible linkage configurations among monomers. However, it has not been elucidated whether subtle structural variations might impact soluble fiber fermentation by colonic microbiota. In this study, we tested the hypothesis that subtle structural variations in a soluble polysaccharide govern the community structure and metabolic output of fermenting microbiota. We performed in vitro fecal fermentation studies using arabinoxylans (AXs) from different classes of wheat (hard red spring [AXHRS], hard red winter [AXHRW], and spring red winter [AXSRW]) with identical initial microbiota. Carbohydrate analyses revealed that AXSRW was characterized by a significantly shorter backbone and increased branching compared with those of the hard varieties. Amplicon sequencing demonstrated that fermentation of AXSRW resulted in a distinct community structure of significantly higher richness and evenness than those of hard-AX-fermenting cultures. AXSRW favored OTUs within Bacteroides, whereas AXHRW and AXHRS favored Prevotella. Accordingly, metabolic output varied between hard and soft varieties; higher propionate production was observed with AXSRW and higher butyrate and acetate with AXHRW and AXHRS. This study showed that subtle changes in the structure of a dietary fiber may strongly influence the composition and function of colonic microbiota, further suggesting that physiological functions of dietary fibers are highly structure dependent. Thus, studies focusing on interactions among dietary fiber, gut microbiota, and health outcomes should better characterize the structures of the carbohydrates employed. IMPORTANCE Diet, especially with respect to consumption of dietary fibers, is well recognized as one of the most important factors shaping the colonic microbiota composition. Accordingly, many studies have been conducted to explore dietary fiber types that could predictably manipulate the colonic microbiota for improved health. However, the majority of these studies underappreciate the vastness of fiber structures in terms of their microbial utilization and omit detailed carbohydrate structural analysis. In some cases, this causes conflicting results to arise between studies using (theoretically) the same fibers. In this investigation, by performing in vitro fecal fermentation studies using bran arabinoxylans obtained from different classes of wheat, we showed that even subtle changes in the structure of a dietary fiber result in divergent microbial communities and metabolic outputs. This underscores the need for much higher structural resolution in studies investigating interactions of dietary fibers with gut microbiota, both in vitro and in vivo.

Waxy potato amylopectin has longer internal and external linear chains than rice or corn amylopectin that are capable of retrograding to a higher degree, but its molecular recrystallization is impeded by unprotonated phosphate groups. Here, we studied whether retrogradation and gel properties of waxy potato starch can be enhanced by lowering pH. The gel strength of waxy potato starch was strongly inversely correlated with pH, going from 10 to 4, and its magnitude was higher at pH values in which the ζ potential of the system was low. Waxy potato starch formed a strong aggregate gel driven by the formation of intermolecular double helices (G' drop25-95 °C ≈ 1358 Pa, melting ΔH = 9.5 J/g) when conditions that reduce electrostatic repulsion (pH 4, ζ = -1.7) are used, a phenomenon that was not observed in low-phosphorylated waxy cereal starches (i.e., waxy rice and corn).

Objectives Maltase-glucoamylase (Mgam) and sucrase-isomaltase (Si) are mucosal α-glucosidases required for the digestion of starch to glucose. We hypothesized that a dietary approach to reduce Mgam and Si activities can reduce glucose generation and absorption, and improve glucose control. Methods Rice starch was entrapped in alginate microspheres to moderate in vitro digestion properties. Three groups of 8-wk old mice (n = 8) were conditioned for 7 d with low 13C-starch-based materials differing in digestion rates (fast, slow, and slower), and then given a digestible 13C-labeled cornstarch test feeding to determine its digestion to glucose. Results Conditioning of the small intestine with the slowly digestible starches for 7 d reduced jejunal α-glucosidase and sucrase activities, as well as glucose absorption for the slowly digestible starch slower group (P Conclusions Decreased glucogenesis from a digestible starch feeding was found in mice conditioned on slowly digestible starch diets, suggesting that a dietary approach incorporating slowly digestible starches may change α-glucosidase activities to moderate glucose absorption rate.

Background Variability in the health effects of dietary fiber might arise from inter-individual differences in the gut microbiota’s ability to ferment these substrates into beneficial metabolites. Our understanding of what drives this individuality is vastly incomplete and will require an ecological perspective as microbiomes function as complex inter-connected communities. Here, we performed a parallel two-arm, exploratory randomized controlled trial in 31 adults with overweight and class-I obesity to characterize the effects of long-chain, complex arabinoxylan (n = 15) at high supplementation doses (female: 25 g/day; male: 35 g/day) on gut microbiota composition and short-chain fatty acid production as compared to microcrystalline cellulose (n = 16, non-fermentable control), and integrated the findings using an ecological framework. Results Arabinoxylan resulted in a global shift in fecal bacterial community composition, reduced α-diversity, and the promotion of specific taxa, including operational taxonomic units related to Bifidobacterium longum, Blautia obeum, and Prevotella copri. Arabinoxylan further increased fecal propionate concentrations (p = 0.012, Friedman’s test), an effect that showed two distinct groupings of temporal responses in participants. The two groups showed differences in compositional shifts of the microbiota (p ≤ 0.025, PERMANOVA), and multiple linear regression (MLR) analyses revealed that the propionate response was predictable through shifts and, to a lesser degree, baseline composition of the microbiota. Principal components (PCs) derived from community data were better predictors in MLR models as compared to single taxa, indicating that arabinoxylan fermentation is the result of multi-species interactions within microbiomes. Conclusion This study showed that long-chain arabinoxylan modulates both microbiota composition and the output of health-relevant SCFAs, providing information for a more targeted application of this fiber. Variation in propionate production was linked to both compositional shifts and baseline composition, with PCs derived from shifts of the global microbial community showing the strongest associations. These findings constitute a proof-of-concept for the merit of an ecological framework that considers features of the wider gut microbial community for the prediction of metabolic outcomes of dietary fiber fermentation. This provides a basis to personalize the use of dietary fiber in nutritional application and to stratify human populations by relevant gut microbiota features to account for the inconsistent health effects in human intervention studies. Trial registration Clinicaltrials.gov, NCT02322112, registered on July 3, 2015.

Consumption of slowly digestible and resistant starches (SDS and RS) is known to modulate postprandial glucose levels and attain extended glucose release. In this study, pregelatinized high-amylose maize starches (50 and 70 g amylose 100 g−1 starch) were subjected to hydrothermal treatments [40 g water 100 g−1, heat-moisture treated (HMT) at 100 °C and low temperature-moisture treated (LMT) at 4 °C] to increase total amount of SDS and RS. Hydrothermal treatment of pregelatinized high-amylose starches produced higher amounts of SDS (27.0 and 26.4% for HMT and LMT amylomaize V, and 21.5 and 21.6% for HMT and LMT amylomaize VII) and RS (36.2 and 31.5 g/100 g, and 47.5 and 37.5 g/100 g, respectively), than pregelatinized normal or waxy starches (SDS - 2.3 and 3.2 g/100 g, and 13.7 and 15.8 g/100 g, respectively; and RS 10.2 and 7.8 g/100 g, and 12.4 and 11.0 g/100 g, respectively). Granule morphology was retained in pregelatinized high-amylose starches, apparently due to their restricted swelling. Starch debranching profiles showed a minor increase in DP 25-36 in SDS and RS, suggesting that higher intermediate fractions of the high-amylose starches may create an overall material effect resulting in slower digestion of hydrothermal treated starches. High SDS and RS in pregelatinized starches could be applied in cold-formed food products.

Amylose is a linear polymer formed by α-1,4 linkages and one of the major components of starch. It is often used to encapsulate hydrophobic molecules of health benefit, such as fatty acids (FA), flavonoids or polyphenols. Amylose and linoleic acid form a complex when the amylose molecule is folded in a V-type conformation. However, it is still not clear how amylose and linoleic acid interact with each other and what is the conformation of the complex adopts under different conditions. Molecular dynamics (MD) simulation is a useful tool used to describe the structure of molecules and complex systems. In this work, MD simulations were used to illustrate conformational changes of the amylose-FA complex and the single amylose molecule, which was used as a reference, in water. During simulations, the conformation of the complex remained stable and the linoleic acid and the amylose molecules formed a helical structure. Furthermore, fatty acid molecules were located in cavity of the amylose helix with the hydrophobic tail inside it. Results also showed that 4C1 was the predominant ring conformation of glucose unit in amylose during interaction with fatty acids. Once the fatty acid was able to form the complex with amylose, the inter turn hydrogen bonds between O6 and neighboring O2/O3 groups were preferentially retained and allowed the complex to keep its helix conformation. Our analysis also shows that the amylose-linoleic acid complex is slightly less stable than the one formed between stearic acid and amylose.

Consumption of traditional West African pearl millet (Pennisetum glaucum) couscous delayed gastric emptying in our recent human study compared to other starch-based foods (white rice, boiled potatoes, pasta). The objective of this study was to determine whether physical properties of pearl millet couscous affect particle breakdown and starch hydrolysis during simulated gastric digestion to understand the basis of the slow gastric emptying. Starch fine structure and viscosity were analyzed for initial millet and wheat couscous samples by high performance size-exclusion chromatography and the Rapid Visco Analyzer, respectively. Couscous samples were subjected to simulated gastric digestion using the Human Gastric Simulator (HGS), a dynamic model of human gastric digestion. Digesta was collected from the HGS at 30 min intervals over 180 min. Particle size and percent starch hydrolysis of couscous in the digesta were evaluated at each time point. The number of particles per gram of dry mass substantially increased over digestion time for millet couscous (p < 0.05), while changed little for the wheat couscous samples. Millet couscous showed lower starch hydrolysis per unit surface area of particles than wheat couscous (p < 0.05). Slower starch hydrolysis was associated with smaller (p < 0.05) amylose chain length for millet (839–963 DP) than for wheat (1225–1563 DP), which may enable enable a denser packing of millet starch molecules that impedes hydrolysis. We hypothesize that the slow gastric emptying rate of millet couscous observed in humans may be explained by its slow starch hydrolysis property that could activate the ileal brake system, independent of high particle breakdown rate in the stomach.

Sulfinate esters were prepared by the process of activating p-toluenesulfinic acid with either cyanuric chloride, methanesulfonyl chloride, or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC-HCl). Activation of p-toluenesulfinic acid with cyanuric chloride led to the formation of sulfinate esters that were accompanied by the formation of the corresponding sulfones. The use of methanesulfonyl chloride for activation via methanesulfonic p-toluenesulfinic anhydride afforded mixtures of sulfinate esters and methanesulfonates. The use of the carbodiimide EDC proved to yield the best results with the highly selective formation of the target sulfinate esters. The use of trimethylacetic p-toluenesulfinic anhydride or cyanuric chloride to achieve the synthesis of sulfinamides proved to be ineffective due to poor chemoselectivity of the nucleophilic attack on the activated p-toluenesulfinic acid anhydride. Ultimately, the use of EDC-HCl to form the sulfinamides proved to be the best pathway for synthesis.

Beneficial effects of some phenolic compounds in modulation of carbohydrate digestion and glycemic response have been reported, however effects of phenolics from processed potato products on these endpoints are not well known. The aims of this study were to characterize phenolic profiles of fresh potatoes (purple, red, or white fleshed; 2 varieties each) and chips, and to examine the potential for potato phenolic extracts (PPE) to modulate starch digestion and intestinal glucose transport in model systems. Following in vitro assessment, a pilot clinical study (n=11) assessed differences in glycemic response and gastric emptying between chips from pigmented and white potatoes. We hypothesized that phenolics from pigmented potato chips would be recovered through processing and result in a reduced acute glycemic response in humans relative to chips made from white potatoes. PPEs were rich in anthocyanins (~98, 11 and ND mg/100 g dw) and chlorogenic acids (~519, 425 and 157 mg/100 g dw) for purple, red and white varieties respectively. While no significant effects were observed on starch digestion by α-amylase and the α-glucosidases, PPEs significantly (p

Understanding the fermentation profiles of dietary fibres in the different regions of the large intestine is needed to design dietary strategies for desired outcomes related to health such as targeting region-specific diseases. In order to test how variably fermentable dietary fibres affect microbial fermentation metabolites in different regions of the large intestine, mice were fed with fructooligosaccharides (FOS, fast fermentation rate), resistant starch type 2 (native potato, RS2, moderate fermentation rate), starch-entrapped microspheres (SM, very slow fermentation rate), and lignin (control) for 14 days. Analysis of intestinal contents obtained from the cecum, proximal colon, and distal colon revealed that short-chain fatty acid (SCFA) metabolites as well as branched-chain fatty acids (BCFA) levels in different regions of the large intestine were influenced by fibre type and rate of fermentation. Slower fermenting resistant starch-based fibres (RS2 and SM) produced more butyrate than FOS in the proximal and distal colon regions. SM substantially lowered the amount of total BCFAs in the distal colon compared to FOS, suggesting that SM promotes delayed saccharolytic activity throughout the colon. Moreover, the microbial analysis done with length-heterogeneity-PCR showed that all fermentable substrates shifted the microbial community with respect to the control group. Overall, our findings show that the type and amount of SCFAs and BCFAs generated in different regions of the large intestine is dietary fibre type and fermentation rate dependent, which should be considered for increasing the health promoting effects of dietary fibres.

While increasing cases related to gluten intolerance have encouraged scientists to develop healthier and better-quality gluten-free products, a more ideal viscoelastic behavior is still needed. In this study, we systematically investigated a dough system composed of corn zein, starch, and additional protein (5% of total protein, termed "co-protein") to achieve similar rheological properties of wheat dough. Three types of starches (corn, wheat, and rice) and four types of co-proteins (casein, sodium caseinate, gliadin, and glutenin) were combined with zein at room temperature and at 35 °C, above zein's glass transition temperature. In small and large deformation tests, only rice starch was found to improve significantly the functionality of zein dough, resulting in formulations with similar rheological properties to wheat dough, i.e., low phase angle value, high complex modulus, and high extensional viscosity implying an elastic dough with high strength and resistance to deformation. Rice starch also significantly lowered glass transition temperature of zein dough, associated with improved performance even at room temperature. Combining zein with a proper starch type, and in cases co-proteins, substantially improved rheological properties of zein dough similar to that of wheat dough, with potential implications to the gluten-free and the plant-based protein market.

Complete starch extraction has been a problem in the corn wet-milling, and here enzymes affecting different structures were used to provide a thorough understanding of the contribution of those structures to starch and protein retention for a way to achieve higher extraction rates. The combination of Frontia Fiberwash® (mix of cellulases and xylanases) and Olexa® (protease) led to an increase in starch (4.5 %) and protein (3.0 %) extraction. Enzymes changed secondary structure composition of proteins due to change in concentration of protein sub-fractions. The protein matrix around starch granules, the key factor for starch retention, was weakened with reducing agents/acids or ultrasound, which better separated starch and protein bodies. Chemicals led to 3.3–5.4 % and 0.7–1.7 % increase in starch and protein extraction, respectively, whereas an ultrasound treatment resulted in 2.2 % and 0.6 % increase. Overall, the study showed starch granules and protein bodies can be freed from wet-milled fiber fraction leading to higher extraction rate when the protein matrix is loosened.

Complete starch extraction has long been an issue in the wet-milling industry, and here structures in the fine and coarse fiber fractions that retain starch were identified and quantified for potential treatments to increase starch and protein extraction rates. Six main structures were identified in the fiber fraction and three of them were directly related to the retention of starch granules. Elemental composition analysis to quantify the contribution of structures responsible for starch retention showed that the protein matrix contributed to 54 % of total starch retention. Confocal microscopy showed that starch granules in the peripheral region of vitreous endosperm were embedded in the protein matrix, whereas the ones in the central region were either stuck in the cell wall polysaccharides or almost free to be liberated. Secondary structural composition of proteins showed differences in fine and coarse fiber fractions. Protein disruption would lead to the largest increase in starch extraction.

Polysaccharides MP-A, MP-U and MP-C were extracted from Mesona chinensis Benth by hot-alkali extraction (HAE), ultrasonic-assisted extraction (UAE) and cellulose-enzyme assisted extraction (CAE), respectively. The yields, physicochemical properties and antioxidant of polysaccharides were investigated. Results showed that the yields of MP-A (11.14%), MP-U (10.62%) and MP-C (9.70%) were similar, and they were all heteropolysaccharides with average molecular weights of 1.9×105Da, 1.5×105Da, 1.4×105Da. Glucose, galactose, and galacturonic acid were the main monosaccharides in MP-A, MP-U and MP-C with molar ratios of 1.00:1.34:0.25, 1.00:2.49:0.19 and 1.00:2.95:0.84, respectively. MP-C extracted by CAE exhibited higher antioxidant activities in FRAP, DPPH, hydroxyl radical assays and the H2O2-induced injury cell model. The three extraction methods had only slight effects on chemical composition, while MP-C extracted by CAE exhibited the highest antioxidant activity, which could potentially be used for an addition ingredient as it was previously shown to have good gelling property in food products.

Consumption of whole vs. refined grain foods is recommended by nutrition or dietary guideline authorities of many countries, yet specific aspects of whole grains leading to health benefits are not well understood. Gastric emptying rate is an important consideration, as it is tied to nutrient delivery rate and influences glycemic response. Our objective was to explore two aspects of cooked rice related to gastric emptying, (1) whole grain brown vs. white rice and (2) potential effect of elevated levels of slowly digestible starch (SDS) and resistant starch (RS) from high-amylose rice. Ten healthy adult participants were recruited for a crossover design study involving acute feeding and testing of 6 rice samples (50 g available carbohydrate). Gastric emptying rate was measured using a 13C-labeled octanoic acid breath test. A rice variety (Cocodrie) with high-amylose content was temperature-cycled to increase SDS and RS fractions. In vitro starch digestibility results showed incremental increase in RS in Cocodrie after two temperature cycles. For low-amylose varieties, SDS was higher in the brown rice form. In human subjects, low-amylose and high-amylose brown rice delayed gastric emptying compared to white rices regardless of amylose content or temperature-cycling (p

An N 4 - p -methoxybenzyloxadiazinone has been prepared from (1 R ,2 S )-norephedrine through a process of reductive amination, N-nitrosation, reduction, and cyclization. The oxadiazinone was acylated and employed in the asymmetric aldol addition reaction with aromatic and aliphatic aldehydes to yield aldol adducts in isolated yields ranging from 54% to 90%. Selected aldol adducts were treated with ceric ammonium nitrate in aqueous acetonitrile to afford the desired β-hydroxycarboxylic acids through a tandem process of oxidative cleavage of the N 4 - p -methoxybenzyl group and acidic hydrolysis of the N 3 -acyl side chain. The β-hydroxycarboxylic acids were recovered in high diastereomeric purity as determined by 500 MHz 1 H NMR spectroscopy and the absolute configuration was confirmed by polarimetry. The chiral auxiliary unit, the 3,4,5,6-tetrahydro-2 H -1,3,4-oxadiazin-2-one (oxadiazinone), was converted into its corresponding 3,6-dihydro-2 H -1,3,4-oxadiazin-2-one (oxadiazinone) through an oxidative pathway promoted by the ceric ammonium nitrate.

A reagent combination of toluenesulfinic acid and trimethylacetyl chloride affords a putative trimethylacetic p-toluenesulfinic anhydride. This reagent has been used to prepare a series of sulfinate esters from primary and secondary alcohols. In addition, the reagent was used to convert Baylis-Hillman substrates into allylic sulfones. Attempts to use the reagent to convert amines to sulfinamides were unsuccessful. In contrast, the use of 2-pyrrolidinone afforded N-p-toluenesulfinyl pyrrolidinone in 64% yield. The use of a chiral 4-benzyl-1,3-oxazolidinone or 4-benzyl-1,3-oxazolidine-2-thione led to the isolation of S-p-tolyl p-toluenethiosulfonate.

Background and objective Although named because of its sucrose hydrolytic activity, this mucosal enzyme plays a leading role in starch digestion because of its maltase and glucoamylase activities. Sucrase-deficient mutant shrews, Suncus murinus, were used as a model to investigate starch digestion in patients with congenital sucrase-isomaltase deficiency.Starch digestion is much more complex than sucrose digestion. Six enzyme activities, 2 α-amylases (Amy), and 4 mucosal α-glucosidases (maltases), including maltase-glucoamylase (Mgam) and sucrase-isomaltase (Si) subunit activities, are needed to digest starch to absorbable free glucose. Amy breaks down insoluble starch to soluble dextrins; mucosal Mgam and Si can either directly digest starch to glucose or convert the post-α-amylolytic dextrins to glucose. Starch digestion is reduced because of sucrase deficiency and oral glucoamylase enzyme supplement can correct the starch maldigestion. The aim of the present study was to measure glucogenesis in suc/suc shrews after feeding of starch and improvement of glucogenesis by oral glucoamylase supplements. Methods Sucrase mutant (suc/suc) and heterozygous (+/suc) shrews were fed with C-enriched starch diets. Glucogenesis derived from starch was measured as blood C-glucose enrichment and oral recombinant C-terminal Mgam glucoamylase (M20) was supplemented to improve starch digestion. Results After feedings, suc/suc and +/suc shrews had different starch digestions as shown by blood glucose enrichment and the suc/suc had lower total glucose concentrations. Oral supplements of glucoamylase increased suc/suc total blood glucose and quantitative starch digestion to glucose. Conclusions Sucrase deficiency, in this model of congenital sucrase-isomaltase deficiency, reduces blood glucose response to starch feeding. Supplementing the diet with oral recombinant glucoamylase significantly improved starch digestion in the sucrase-deficient shrew.

Delivering fibers more distally could be important to prevent or treat colonic diseases such as cancer and ulcerative colitis. Here, we hypothesized that fermentation of fast-fermenting soluble fibers by the colonic microbiota is delayed when they are presented in a mixture due to hierarchical utilization of fibers. A series of in vitro fermentation studies was performed using fecal microbiota obtained from three healthy donors using single dietary fibers [arabinoxylan, chondroitin sulfate (CS), galactomannan (GM), polygalacturonic acid (PGA), xyloglucan (XG)] and a mixture containing an equal amount of each. Substrate disappearance analysis, as measured by GC–MS, revealed that CS, PGA, and XG utilization was delayed when present in the mixture. 16S rRNA sequencing showed certain fibers consistently increased specific genera in the microbiota of all donor groups. Mixing different types of fermentable dietary fibers might be a logical strategy for delivering fibers into more distal regions of the colon.

Introduction Leishmaniasis is an endemic disease caused by the protozoan parasite Leishmania. Current treatments for the parasite are limited by cost, availability and drug resistance as the occurrence of leishmaniasis continues to be more prevalent. Sulfonamides are a class of compounds with medicinal properties which have been used to treat bacterial and parasitic disease via various pathways especially as antimetabolites for folic acid. Methods New derivatives of sulfonamide compounds were assessed for their impact on Leishmania cell viability and potential pathways for inhibition were evaluated. Leishmania tarentolae (ATCC Strain 30143) axenic promastigote cells were grown in brain heart infusion (BHI) medium and treated with varying concentrations of the new sulfonamide compounds. Light microscopy and viability tests were used to assess the cells with and without treatment. Discussion A non-water soluble sulfonamide was determined to have 90-96% viability inhibition 24 hours after treatment with 100 µM final concentration. Because Leishmania are also autotrophs for folate precursors, the folic acid pathway was identified as a target for sulfonamide inhibition. When folic acid was added to untreated Leishmania, cell proliferation increased. A water soluble derivative of the inhibitory sulfonamide was synthesized and evaluated, resulting in less viability inhibition with a single dose (approximately 70% viability inhibition after 24 hours with 100 µM final concentration), but additive inhibition with multiple doses of the compound. Results However, the potential mechanism of inhibition was different between the water-soluble and non-water soluble sulfonamides. The inhibitory effects and potential pathways of inhibition indicate that these compounds may be new treatments for this disease.

Influences of harvest time and storage conditions on activities of fructan:fructan1-fructosyltransferase (1-FFT) and inulin hydrolase (InH) in relation to inulin and soluble sugars of Jerusalem artichoke (Helianthus tuberosus L.) tubers were investigated. Maturity affected 1-FFT-activity, inulin contents, and inulin profiles of the tubers harvested between 30 and 70 days after flowering (DAF). Decreases in 1-FFT activity, high molecular weight inulin, and inulin content were observed in late-harvested tubers. The tubers harvested at 50 DAF had the highest inulin content (734.9 ± 20.5 g kg−1 DW) with a high degree of polymerization (28% of DP >30). During storage of the tubers, increases in InH activity (reached its peak at 15 days of storage) and gradual decreases in 1-FFT activity took placed. These changes were associated with inulin depolymerization, causing decreases in inulin content and increases in soluble sugars. As well, decreasing storage temperatures would retain high inulin content and keep low soluble sugars; and freezing at −18 °C would best retard 1-FFT, InH, and inulin changes.

An N3-(p-methoxyphenoxy)acetyloxazolidine-2-thione has been synthesized and employed in glycolate asymmetric aldol addition reactions with aromatic and aliphatic aldehydes. It was determined that the titanium tetrachloride medicated aldol reaction afforded diastereoselectivities that ranged from 75:25 to 94:6 when the reaction was conducted at −78 °C. The absolute stereochemistry of the aldol adducts was determined by 1H NMR spectroscopy and X-ray crystallography. The 1H NMR spectra of the aldol adducts contained a signal (the α-proton of the glycolate position of the aldol side chain) that was highly deshielded due to conformational restriction about the N(3)-(p-methoxyphenoxy)acetyl side chain and the oxazolidine-2-thione auxiliary.

Depending on their chemical structure, pectic polymers may be fermented by different bacteria in the human gut and, therefore, display a different metabolite profile. We aimed to investigate the chemical structure of pectins from peach palm fruits and to evaluate their in vitro fecal fermentation profiles. A fraction (PW-AP) containing a linear highly methyl esterified homogalacturonan (degree of esterification of 70%) with minor portions of xylogalacturonan and type I rhamnogalacturonan was submitted to fermentation by the human gut microbiota. It produced significantly less gas than fructooligosaccharides (FOS) at all evaluated time points, and in 24 h presented a cumulative gas production ~27% lower than FOS. Drops in pH could be observed during fermentation of both FOS and PW-AP. Moreover, the pectin was slower fermented than FOS, though with a similar production of total short chain fatty acids (SCFA) and a lower production of branched chain fatty acids. The amounts of specific SCFA differed from that of FOS, with higher production of acetate (16.2%) and propionate (6.2%) and lower production butyrate (112%). The ratio of total SCFA production to gas production was 4.0 mL/µmol and 5.5 mL/µmol for FOS and PW-AP, respectively, indicating that the latter leads to less gas formation per µmol of produced SCFA. Overall, the understanding of how pectic structures are fermented brings new insights into the fiber utilization by the human gut microbiota and its relation to biological outcomes.

Impaired gut barrier function plays an important role in the development of many diseases such as obesity, inflammatory bowel disease, and in HIV infection. Dietary fibres have been shown to improve intestinal barrier function through their fermentation products, short chain fatty acids (SCFAs), and the effects of individual SCFAs have been studied. Here, different SCFA mixtures representing possible compositions from fibre fermentation products were studied for protective and reparative effects on intestinal barrier function. The effect of fermentation products from four dietary fibres, i.e. resistant starch, fructooligosaccharides, and sorghum and corn arabinoxylan (varying in their branched structure) on barrier function was positively correlated with their SCFA concentration. Pure SCFA mixtures of various concentrations and compositions were tested using a Caco-2 cell model. SCFAs at a moderate concentration (40-80 mM) improved barrier function without causing damage to the monolayer. In a 40 mM SCFA mixture, the butyrate proportion at 20% and 50% showed both a protective and a reparative effect on the monolayer to disrupting agents (LPS/TNF-α) applied simultaneously or prior to the SCFA mixtures. Relating this result to dietary fibre selection, slow fermenting fibres that deliver appropriate concentrations of SCFAs to the epithelium with a high proportion of butyrate may improve barrier function.

OBJECTIVES: Our laboratory has recently shown that slowly digestible starch (SDS) that locationally digests to the ileum activates the gut-brain axis and reduces food intake in obese animals. Glucagon-like peptide-1 (GLP-1), oxyntomodulin (OXM), and peptide YY (PYY) are the main appetite-suppressing (anorexigenic) peptides of the intestinal enterendocrine L-cells that regulate postprandial insulin levels and satiety signals. We investigated the in vitro L-cell chemosensation of α-amylase starch digestion products, named maltooligosaccharides (MOS), and using SDS to deliver MOS in vivo. METHODS: Mouse (STC-1) and human (NCI-H716) cells were used to test chemosensation response and release of GLP-1, OXM and PYY after MOS treatment. Differential gene expression and comparable global protein profiling of STC-1 cell treated with MOS was tested using RNA sequencing and LC-MS/MS analysis. Alginate-entrapped SDS microspheres that digest distally into the ileum were used to examine the role of SDS in the intervention and prevention of obesity in C57BL/6 J obese and lean mice, respectively. Body weight, food intake and body composition were monitored periodically. RESULTS: MOS exhibited significantly higher stimulatory effect on GLP-1 and OXM secretion in mouse and human L-cells, respectively, compared to glucose. Multi-omics analysis showed that MOS induced exocytosis of GLP-1- and OXM-containing vesicles and did not induce positive regulation of the proglucagon gene suggesting that secretion, but not synthesis, of the proglucagon gene products was enhanced by MOS. In vivo Results showed that 20% SDS in low-fat diets significantly improved weight loss and food intake reduction in obese mice. Similarly, 15% SDS in high-fat diets showed significant reduction in body fat %, increase in lean body mass, and considerable reduction in weight gain rate and food intake in lean mice fed on high-fat diets. CONCLUSIONS: We propose several insights into L-cell sensation of dietary starch-degraded MOS delivered by the consumption of slowly digestible starch. MOS exhibit unique influences on L-cell sensitivity and gut hormone productivity. The intricate role of dietary carbohydrates on gut physiological response, related to satiety and food intake could be a new approach for design of foods for obesity prevention. FUNDING SOURCES: Whistler Center for Carbohydrate Research, Purdue University. Supporting Tables, Images and/or Graphs

Insoluble fermentable cell wall matrix fibers have been shown to support beneficial butyrogenic gut Clostridia, but have restricted use in food products. Here, a soluble fiber matrix was developed that exhibited a similar effect. A low arabinose/xylose ratio corn bran arabinoxylan (CAX) was extracted with two concentrations of sodium hydroxide, 0.25 M and 1.5 M, to give soluble polymers with relatively low (L) and high (H) residual levels of bound ferulic acid (FA) (CAX-LFA and CAX-HFA). After laccase treatment to make diferulate crosslinks, soluble matrices were formed with average 3.5 to 4.5 mer. In vitro human fecal fermentation of CAX-LFA, CAX-HFA, soluble crosslinked ∼3.5 mer CAX-LFA (SCCAX-LFA), and ∼4.5 mer SCCAX-HFA revealed that the SCCAX matrices had somewhat slower fermentation properties by measuring the gas production, total short chain fatty acids, and carbohydrate disappearance, with a higher butyrate proportion in SCCAX-HFA. 16S rRNA gene sequencing showed that SCCAX-HFA promoted OTUs associated with butyrate production including unassigned Ruminococcaceae, unassigned Blautia, Fecalibacterium prausnitzii, and unassigned Clostridium. Thus, when the physical form of an individual soluble polysaccharide was changed to a soluble crosslinked matrix, in vitro fermentation was shifted to Clostridial butyrate producers. This study shows that the physical form of the fiber influences the competition for substrate among the gut bacteria. Crosslinking of soluble fibers may be a strategy for developing soluble matrices with good physical functionalities for beverages and other foods to improve gut health.