Interactions between dietary fibre-rich preparations and glycoconjugated bile acids in vitro

Cocoa shell ingredients improve their lipid-lowering properties under simulated digestion: In vitro and HepG2 cells study

Cocoa (Theobroma cacao) shell, the main by-product of cocoa industry, is associated with the regulation of several biomarkers of metabolic syndrome. However, there is little information about the digestion effect on the physiological properties of cocoa shell. The aim of this study was to assess the impact of a standardized in vitro digestion protocol on the hypolipidemic capacity of two cocoa shell ingredients, a flour (CSF) and an aqueous extract (CSE), through the evaluation of their in vitro hypolipidemic properties and lipid-lowering effects in HepG2 cells. CSF and CSE digested fractions increased their capacity to bind primary bile acids (16-88 %) and inhibit lipase activity (41-100 %), while their ability to bind secondary bile acids (33-42 %) was maintained. Likewise, the digested fractions of cocoa shell ingredients reduced the solubility of the cholesterol micelles (35-97 %) and inhibited the hydroxymethylglutaryl-Co-enzyme A reductase (HMGCR) activity (18-100 %). The hypolipidemic properties of non-digested fractions further enhanced the CSF potential to decrease lipid absorption. Cocoa shell ingredients demonstrated lipid-lowering properties after simulated digestion by effectively reducing the accumulation of intracellular lipids (78-122 %), triacylglycerides (60-90 %), and cholesterol (100 %) induced by palmitic acid in hepatic cells. These results were confirmed by their ability to stimulate lipolysis, reducing the increase in lipase activity (28-78 %) and increasing glycerol release (27-80 %) with respect to palmitic acid treated cells, and inhibiting HMGCR activity. Phenolic compounds and dietary fiber are significantly associated to the observed hypolipidemic effects of cocoa shell ingredients. These findings demonstrated the potential efficacy of CSF and CSE in reducing lipid absorption and reversing its hepatic accumulation. Hence, these cocoa shell ingredients might prevent diseases related to lipid accumulation by improving overall health status.

Cholesterol-Lowering Effect of Polysaccharides from Cyclocarya paliurus In Vitro and in Hypercholesterolemia Mice

In this study, a new component of Cyclocarya paliurus polysaccharides (CPP20) was precipitated by the gradient ethanol method, and the protective effect of CPP20 on hypercholesterolemia mice was investigated. In vitro, CPP20 had the ability to bind bile salts and inhibit cholesterol micelle solubility, and it could effectively clear free radicals (DPPH•, •OH, and ABTS+). In vivo, CPP20 effectively alleviated hypercholesterolemia and liver damage in mice. After CPP20 intervention, the activity of antioxidant enzymes (SOD, CAT, and GSH-Px) and the level of HDL-C in liver and serum were increased, and the activity of aminotransferase (ALT and AST) and the level of MDA, TC, TG, LDL-C, and TBA were decreased. Molecular experiments showed that CPP20 reduced cholesterol by regulating the mRNA expression of antioxidation-related genes (SOD, GSH-Px, and CAT) and genes related to the cholesterol metabolism (CYP7A1, CYP27A1, SREBP-2, HMGCR, and FXR) in liver. In addition, CPP20 alleviated intestinal microbiota disturbances in mice with hypercholesterolemia and increased levels of SCFAs. Therefore, CPP20 alleviates hypercholesterolemia by alleviating oxidative damage, maintaining cholesterol homeostasis, and regulating gut microbiota.

Self-assembly of coconut residue fiber with chitosan: Effect of three pre-treatments on the self-assembly process and bile salt adsorption

Self-assembly with chitosan is a promising method for improving bile salt (BS) adsorption by coconut residue fiber (CRF). To study the self-assembly process, three pre-treatments were performed and investigated using microrheological analysis. The effects of the pretreatments on the self-assembly of CRF and the BS adsorption were evaluated. During self-assembly, CRFs underwent Brownian-like motion, and the addition of chitosan facilitated the formation of inter-particle interactions between CRFs in the system. These interactions were small in extent, large in number, and slow to state change, in addition to relatively high strength and longer maintenance, all of which contributed to the binding to BS. The conventional pretreatments failed to effectively improve the BS adsorption of the self-assembled CRFs and weakened the inter-particle interactions in the system. These results suggest that chitosan assists in the adsorption of self-assembled CRF to BS through a combination of H-bonds and other weak intermolecular forces.

Dietary Bamboo Charcoal Decreased Visceral Adipose Tissue Weight by Enhancing Fecal Lipid Excretions in Mice with High-Fat Diet-Induced Obesity

Bamboo charcoal (BC) powder is prepared from thick bamboo stems via dry distillation and is often used for food coloring. Due to the unique structure of the micropores in bamboo stems, BC powder also serves as an indigestible carrier to prevent the absorption of toxic substances and nutrients from the digestive tract. This study evaluated the health-promoting function of BC, particularly its effects in decreasing visceral adipose tissue in a mouse model with high-fat diet (HFD)-induced obesity. Four-week-old male C57BL/6J mice were divided into three groups and fed either a low-fat (LF) diet (7% fat), HF diet (25% fat), or HF diet with 0.5% BC (HF-BC). After 80 days, the HF-BC diet was found to have decreased epididymal and mesenteric white adipose tissue weights compared to HFD. The inhibition of visceral fat accumulation by BC intake was partly due to enhanced fecal fatty acid excretion induced by its bile acid-binding and pancreatic lipase inhibition. Contrarily, the gut microbiota, known to influence systemic energy metabolism, did not change significantly between the HF and HF-BC groups. These results indicate that dietary BC inhibits visceral fat accumulation, which could reduce obesity development.

Properties of plant-derived soluble dietary fibers for fiber-enriched foods: A comparative evaluation

Plant-derived soluble dietary fibers (SDF) have many important physiological functions and the applications of SDF vary based on their properties, which are worth further investigating for fiber-enriched food production. In this study, SDF derived from konjac, apple, chicory, flaxseed, orange, psyllium seed, soybean and oat were purified, and their structural, physicochemical and functional properties were systematically evaluated. Monosaccharide composition analysis showed that these SDF belonged to heteropolysaccharides, of which konjac, psyllium seed, apple, soybean and oat SDF were glucomannan, arabinoxylan, pectin, arabinogalactan and glucan, respectively. The molecular weight of konjac glucomannan (KGM, 5.22 × 10⁶ Da) was the highest, and inulin, soybean arabinogalactan (SA) and oat glucan (OG) had higher water solubility. Moreover, KGM, apple pectin (AP), flaxseed SDF (FS) and psyllium seed arabinoxylan (PA) exhibited better water-holding capacity, swelling capacity, emulsifying activity and stability. Rheological studies and texture profile analysis suggested that KGM had the best viscosity and gelation ability. In addition, AP and orange SDF (OS) showed better α-amylase inhibitory activity, while OS and KGM had higher pancreatic lipase inhibitory activity. Also, KGM and FS displayed fine cholesterol absorption capacity. To summary, these functional properties illustrated the feasibility of SDF to regulate blood sugar and blood lipid levels.

A Review on Rhubarb-Derived Substances as Modulators of Cardiovascular Risk Factors—A Special Emphasis on Anti-Obesity Action

The currently available anti-obesity therapies encounter many associated risks and side effects often causing the ineffectiveness of treatment. Therefore, various plant-derived substances have been extensively studied as a promising support or even an alternative for existing anti-obesity therapies. This review is dealing with the anti-obesity potential of edible and ethnomedicinal rhubarb species and emerging possible role of the rhubarb-derived extracts or individual compounds in the prevention of obesity and perspectives for their use in an anti-obesity treatment. A special emphasis is put on the most popular edible specimens, i.e., Rheum rhabarbarum L. (garden rhubarb) and Rheum rhaponticum L. (rhapontic rhubarb, Siberian rhubarb); however, the anti-obesity potential of other rhubarb species (e.g., R. officinale, R. palmatum, and R. emodi) is presented as well. The significance of rhubarb-derived extracts and low-molecular specialized rhubarb metabolites of diversified chemical background, e.g., anthraquinones and stilbenes, as potential modulators of human metabolism is highlighted, including the context of cardiovascular disease prevention. The available reports present multiple encouraging rhubarb properties starting from the anti-lipidemic action of rhubarb fibre or its use as purgative medicines, through various actions of rhubarb-derived extracts and their individual compounds: inhibition of enzymes of cholesterol and lipid metabolism, targeting of key molecular regulators of adipogenesis, regulators of cell energy metabolism, the ability to inhibit pro-inflammatory signalling pathways and to regulate glucose and lipid homeostasis contributing to overall in vivo and clinical anti-obesity effects.

Biophysical insights into modulating lipid digestion in food emulsions

During the last decade, major scientific advances on understanding the mechanisms of lipid digestion and metabolism have been made, with a view to addressing health issues (such as obesity) associated with overconsumption of lipid-rich and sucrose-rich foods. As lipids in common foods exist in the form of emulsions, the structuring of emulsions has been one the main strategies for controlling the rate of lipid digestion and absorption, at least from a colloid science viewpoint. Modulating the kinetics of lipid digestion and absorption offers interesting possibilities for developing foods that can provide control of postprandial lipaemia and control the release of lipophilic compounds. Food emulsions can be designed to achieve considerable differences in the kinetics of lipid digestion but most research has been applied to relatively simple model systems and in in vitro digestion models. Further research to translate this knowledge into more complex food systems and to validate the results in human studies is required. One promising approach to delay/control lipid digestion is to alter the stomach emptying rate of lipids, which is largely affected by interactions of emulsion droplets with the food matrices. Food matrices with different responses to the gastric environment and with different interactions between oil droplets and the food matrix can be designed to influence lipid digestion. This review focuses on key scientific advances made during the last decade on understanding the physicochemical and structural modifications of emulsified lipids, mainly from a biophysical science perspective. The review specifically explores different approaches by which the structure and stability of emulsions may be altered to achieve specific lipid digestion kinetics.

Polysaccharide Structures and Their Hypocholesterolemic Potential

Several classes of polysaccharides have been described to have hypocholesterolemic potential, namely cholesterol bioaccessibility and bioavailability. This review will highlight the main mechanisms by which polysaccharides are known to affect cholesterol homeostasis at the intestine, namely the effect (i) of polysaccharide viscosity and its influence on cholesterol bioaccessibility; (ii) on bile salt sequestration and its dependence on the structural diversity of polysaccharides; (iii) of bio-transformations of polysaccharides and bile salts by the gut microbiota. Different quantitative structure–hypocholesterolemic activity relationships have been explored depending on the mechanism involved, and these were based on polysaccharide physicochemical properties, such as sugar composition and ramification degree, linkage type, size/molecular weight, and charge. The information gathered will support the rationalization of polysaccharides’ effect on cholesterol homeostasis and highlight predictive rules towards the development of customized hypocholesterolemic functional food.

Characterization of insoluble dietary fiber from three food sources and their potential hypoglycemic and hypolipidemic effects

Dietary fiber is an important nutrient for improving human health and controlling calorie intake, and is used to produce functional foods. In this study, insoluble dietary fiber (IDF) from three sources (enoki mushrooms, carrots, and oats) was characterized and their hypoglycemic and hypolipidemic effects were determined with in vitro and in vivo models. The results of Scanning electron microscopy (SEM) showed that the IDF from the three sources have different morphologies. The Fourier transform infrared spectroscopy (FT-IR) results showed that the IDF samples from the three sources have similar active groups, but the X-ray diffraction (XRD) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) results indicated that oat IDF mainly contained cellulose, and enoki mushroom IDF and carrot IDF contained hemicelluloses and cellulose. Among three IDF, carrot IDF had stronger water holding capacity, swelling capacity, and adsorption capacity of oil and cholate; enoki mushroom IDF had stronger glucose adsorption capacity and the ability to inhibit fat digestion; while oat IDF had stronger cholesterol adsorption capacity. None of the three IDF showed significant inhibition on starch digestion. Results from mouse feeding studies showed that IDF from three sources all improved glucose tolerance and inhibited the rise of blood lipid after the fat loading. Thus, this study demonstrated the functional significance of the IDF from three sources, which provides a reference for their application in functional food products aiming at maintaining healthy glucose and blood lipid levels.

Mechanisms of Interactions between Bile Acids and Plant Compounds-A Review

Plant compounds are described to interact with bile acids during small intestinal digestion. This review will summarise mechanisms of interaction between bile acids and plant compounds, challenges in in vivo and in vitro analyses, and possible consequences on health. The main mechanisms of interaction assume that increased viscosity during digestion results in reduced micellar mobility of bile acids, or that bile acids and plant compounds are associated or complexed at the molecular level. Increasing viscosity during digestion due to specific dietary fibres is considered a central reason for bile acid retention. Furthermore, hydrophobic interactions are proposed to contribute to bile acid retention in the small intestine. Although frequently hypothesised, no mechanism of permanent binding of bile acids by dietary fibres or indigestible protein fractions has yet been demonstrated. Otherwise, various polyphenolic structures were recently associated with reduced micellar solubility and modification of steroid and bile acid excretion but underlying molecular mechanisms of interaction are not yet fully understood. Therefore, future research activities need to consider the complex composition and cell-wall structures as influenced by processing when investigating bile acid interactions. Furthermore, influences of bile acid interactions on gut microbiota need to be addressed to clarify their role in bile acid metabolism.

Roasting carob flour decreases the capacity to bind glycoconjugates of bile acids

Carob is the fruit obtained from Ceratonia siliqua L. and it is a source of bioactive compounds that have been linked to several health promoting effects, including lowering blood cholesterol concentration.

Bile salts in digestion and transport of lipids

Because of their unusual chemical structure, bile salts (BS) play a fundamental role in intestinal lipid digestion and transport. BS have a planar arrangement of hydrophobic and hydrophilic moieties, which enables the BS molecules to form peculiar self-assembled structures in aqueous solutions. This molecular arrangement also has an influence on specific interactions of BS with lipid molecules and other compounds of ingested food and digestive media. Those comprise the complex scenario in which lipolysis occurs. In this review, we discuss the BS synthesis, composition, bulk interactions and mode of action during lipid digestion and transport. We look specifically into surfactant-related functions of BS that affect lipolysis, such as interactions with dietary fibre and emulsifiers, the interfacial activity in facilitating lipase and colipase anchoring to the lipid substrate interface, and finally the role of BS in the intestinal transport of lipids. Unravelling the roles of BS in the processing of lipids in the gastrointestinal tract requires a detailed analysis of their interactions with different compounds. We provide an update on the most recent findings concerning two areas of BS involvement: lipolysis and intestinal transport. We first explore the interactions of BS with various dietary fibres and food emulsifiers in bulk and at interfaces, as these appear to be key aspects for understanding interactions with digestive media. Next, we explore the interactions of BS with components of the intestinal digestion environment, and the role of BS in displacing material from the oil-water interface and facilitating adsorption of lipase. We look into the process of desorption, solubilisation of lipolysis, products and formation of mixed micelles. Finally, the BS-driven interactions of colloidal particles with the small intestinal mucus layer are considered, providing new findings for the overall assessment of the role of BS in lipid digestion and intestinal transport. This review offers a unique compilation of well-established and most recent studies dealing with the interactions of BS with food emulsifiers, nanoparticles and dietary fibre, as well as with the luminal compounds of the gut, such as lipase-colipase, triglycerides and intestinal mucus. The combined analysis of these complex interactions may provide crucial information on the pattern and extent of lipid digestion. Such knowledge is important for controlling the uptake of dietary lipids or lipophilic pharmaceuticals in the gastrointestinal tract through the engineering of novel food structures or colloidal drug-delivery systems.

Manipulation of the dry bean (Phaseolus vulgaris L.) matrix by hydrothermal and high-pressure treatments: Impact on in vitro bile salt-binding ability

The capacity of high-fiber foods to sequester BS during digestion is considered a mechanism to lower serum-cholesterol. We investigated the effect of hydrothermal (HT) and high-hydrostatic-pressure (HHP) on the bile salt (BS)-binding ability of dry beans, and how this relates to changes in bean microstructure, fiber content (insoluble-IDF/soluble-SDF), and viscosity. HT and HHP-600 MPa led to significant IDF reduction, including resistant starch (RS), whereas 150-450 MPa significantly increased RS, without modifying IDF/SDF content. Microscopy analysis showed that heating disrupted the bean cell wall integrity, protein matrix and starch granules more severely than 600 MPa; however, tightly-packed complexes of globular starch granules-protein-cell wall fiber formed at HHP ≤ 450 MPa. While HT significantly reduced BS-binding efficiency despite no viscosity change, HHP-treatments maintained or enhanced BS-retention. 600 MPa-treatment induced the maximum BS-binding ability and viscosity. These results demonstrate that BS-binding by beans is not solely based on their fiber content or viscosity, but is influenced by additional microstructural factors.

In Vitro Interactions of Dietary Fibre Enriched Food Ingredients with Primary and Secondary Bile Acids

Dietary fibres are reported to interact with bile acids, preventing their reabsorption and promoting their excretion into the colon. We used a method based on in vitro digestion, dialysis, and kinetic analysis to investigate how dietary fibre enriched food ingredients affect the release of primary and secondary bile acids as related to viscosity and adsorption. As the main bile acids abundant in humans interactions with glyco- and tauroconjugated cholic acid, chenodesoxycholic acid and desoxycholic acid were analysed. Viscous interactions were detected for apple, barley, citrus, lupin, pea, and potato derived ingredients, which slowed the bile acid release rate by up to 80%. Adsorptive interactions of up to 4.7 μmol/100 mg DM were significant in barley, oat, lupin, and maize preparations. As adsorption directly correlated to the hydrophobicity of the bile acids the hypothesis of a hydrophobic linkage between bile acids and dietary fibre is supported. Delayed diffusion in viscous fibre matrices was further associated with the micellar properties of the bile acids. As our results indicate changes in the bile acid pool size and composition due to interactions with dietary fibre rich ingredients, the presented method and results could add to recent fields of bile acid research.

Differentiation of Adsorptive and Viscous Effects of Dietary Fibres on Bile Acid Release by Means of In Vitro Digestion and Dialysis

To explain the cholesterol-reducing effects of dietary fibres, one of the major mechanisms proposed is the reduced reabsorption of bile acids in the ileum. The interaction of dietary fibres with bile acids is associated with their viscous or adsorptive effects. Since these fibre characteristics are difficult to investigate in vivo, suitable in vitro methodologies can contribute to understanding the mechanistic principles. We compared the commonly used centrifugal approach with a modified dialysis method using dietary fibre-rich materials from different sources (i.e., barley, citrus, lupin, and potato). Digestion was simulated in vitro with oral, gastric, and small intestinal digestion environments. The chyme was dialysed and released bile acids were analysed by high-performance liquid chromatography. The centrifugation method showed adsorptive effects only for cholestyramine (reference material) and a high-fibre barley product (1.4 µmol taurocholic acid/100 mg dry matter). Alternatively, the dialysis approach showed higher values of bile acid adsorption (2.3 µmol taurocholic acid/100 mg dry matter) for the high-fibre barley product. This indicated an underestimated adsorption when using the centrifugation method. The results also confirmed that the dialysis method can be used to understand the influence of viscosity on bile acid release. This may be due to entrapment of bile acids in the viscous chyme matrix. Further studies on fibre structure and mechanisms responsible for viscous effects are required to understand the formation of entangled networks responsible for the entrapment of the bile acids.

Re-evaluation of the mechanisms of dietary fibre and implications for macronutrient bioaccessibility, digestion and postprandial metabolism

The positive effects of dietary fibre on health are now widely recognised; however, our understanding of the mechanisms involved in producing such benefits remains unclear. There are even uncertainties about how dietary fibre in plant foods should be defined and analysed. This review attempts to clarify the confusion regarding the mechanisms of action of dietary fibre and deals with current knowledge on the wide variety of dietary fibre materials, comprising mainly of NSP that are not digested by enzymes of the gastrointestinal (GI) tract. These non-digestible materials range from intact cell walls of plant tissues to individual polysaccharide solutions often used in mechanistic studies. We discuss how the structure and properties of fibre are affected during food processing and how this can impact on nutrient digestibility. Dietary fibre can have multiple effects on GI function, including GI transit time and increased digesta viscosity, thereby affecting flow and mixing behaviour. Moreover, cell wall encapsulation influences macronutrient digestibility through limited access to digestive enzymes and/or substrate and product release. Moreover, encapsulation of starch can limit the extent of gelatinisation during hydrothermal processing of plant foods. Emphasis is placed on the effects of diverse forms of fibre on rates and extents of starch and lipid digestion, and how it is important that a better understanding of such interactions with respect to the physiology and biochemistry of digestion is needed. In conclusion, we point to areas of further investigation that are expected to contribute to realisation of the full potential of dietary fibre on health and well-being of humans.

Binding of bile acids by pastry products containing bioactive substances during in vitro digestion

The modern day consumer tends to choose products with health enhancing properties, enriched in bioactive substances. One such bioactive food component is dietary fibre, which shows a number of physiological properties including the binding of bile acids. Dietary fibre should be contained in everyday, easily accessible food products. Therefore, the aim of this study was to determine sorption capacities of primary bile acid (cholic acid - CA) and secondary bile acids (deoxycholic - DCA and lithocholic acids - LCA) by muffins (BM) and cookies (BC) with bioactive substances and control muffins (CM) and cookies (CC) in two sections of the in vitro gastrointestinal tract. Variations in gut flora were also analysed in the process of in vitro digestion of pastry products in a bioreactor. Enzymes: pepsin, pancreatin and bile salts: cholic acid, deoxycholic acid and lithocholic acid were added to the culture. Faecal bacteria, isolated from human large intestine, were added in the section of large intestine. The influence of dietary fibre content in cookies and concentration of bile acids in two stages of digestion were analysed. Generally, pastry goods with bioactive substances were characterized by a higher content of total fibre compared with the control samples. These products also differ in the profile of dietary fibre fractions. Principal Component Analysis (PCA) showed that the bile acid profile after two stages of digestion depends on the quality and quantity of fibre. The bile acid profile after digestion of BM and BC forms one cluster, and with the CM and CC forms a separate cluster. High concentration of H (hemicellulose) is positively correlated with LCA (low binding effect) and negatively correlated with CA and DCA contents. The relative content of bile acids in the second stage of digestion was in some cases above the content in the control sample, particularly LCA. This means that the bacteria introduced in the 2nd stage of digestion synthesize the LCA.

Impact of dietary fibers [methyl cellulose, chitosan, and pectin] on digestion of lipids under simulated gastrointestinal conditions

A simulated in vitro digestion model was used to elucidate the impact of dietary fibers on the digestion rate of emulsified lipids. The influence of polysaccharide type (chitosan (cationic), methyl cellulose (non-ionic), and pectin (anionic)) and initial concentration (0.4 to 3.6% (w/w)) was examined. 2% (w/w) corn oil-in-water emulsions stabilized by 0.2% (w/w) Tween-80 were prepared, mixed with polysaccharide, and then subjected to an in vitro digestion model (37 °C): initial (pH 7.0); oral (pH 6.8; 10 min); gastric (pH 2.5; 120 min); and, intestinal (pH 7.0; 120 min) phases. The impact of polysaccharides on lipid digestion, ζ-potential, particle size, viscosity, and stability was determined. The rate and extent of lipid digestion decreased with increasing pectin, methyl cellulose, and chitosan concentrations. The free fatty acids released after 120 min of lipase digestion were 46, 63, and 81% (w/w) for methyl cellulose, pectin, and chitosan, respectively (3.6% (w/w) initial polysaccharide), indicating that methyl cellulose had the highest capacity to inhibit lipid digestion, followed by pectin, and then chitosan. The impact of the polysaccharides on lipid digestion was attributed to their ability to induce droplet flocculation, and/or due to their interactions with molecular species involved in lipid hydrolysis, such as bile salts, fatty acids, and calcium. These results have important implications for understanding the influence of dietary fibers on lipid digestion. The control of lipid digestibility within the gastrointestinal tract might be important for the development of reduced-calorie emulsion-based functional food products.

Effects of various fibre-rich extracts on cholesterol binding capacity during in vitro digestion of pork patties

Intake of foods containing high levels of cholesterol harms human health, and an increase in the intake of dietary fibre (DF) may mitigate these negative effects.

Chemical composition and bile acid binding activity of products obtained from amaranth (Amaranthus cruentus) seeds

Cardiovascular diseases are currently the greatest cause of mortality in the world, and dislipidemia is appearing as one of the most important risk factors. The binding of bile acids (BAs) has been hypothesized as a possible mechanism by which dietary fibers lower blood cholesterol levels. Besides the fibers, other components in the amaranth seeds may be related to this hypocholesterolemic effect. The objective of the present study was to evaluate the BA binding capacity of some products obtained from defatted amaranth flour (DAF) and from the amaranth protein concentrate (APC). The alkaline residue, rich in fibers (8.6%), presented the lowest binding activity for the BAs tested, with the exception of glycocholic acid. The DAF showed intermediary binding activity for all the BAs tested, although similar to that of the APC for deoxycholic acid, and to that of the amaranth protein hydrolysate (APH) for taurocholic acid. The DAF and APC showed binding activity for secondary bile acids toxic to the intestinal mucus. From the results, amaranth products were shown to have the ability to bind BAs, but it was not possible to affirm whether the main component responsible for this activity was the proteins, fibers or eventually some other non-evaluated component.

Non-extractable procyanidins and lignin are important factors in the bile acid binding and radical scavenging properties of cell wall material in some fruits

The cell wall components and the food functions of alcohol-insoluble solids (AIS) of Chinese quince, quince, hawthorn, apple, pear and blueberry fruits were analyzed. Chinese quince contained characteristically high contents of cellulose, lignin, and non-extractable procyanidins (NEPCs). On the other hand, the quince AIS contained the highest proportion of NEPCs, the highest mean degree of polymerization (mDP), the strongest radical scavenging activity, and strong bile acid binding activity. In fruit AIS, the lignin and NEPC contents both showed positive correlations with the bile acid binding and radical scavenging activities. The value for mDP × NEPC content was a good index for the radical scavenging activity. The results suggest that highly polymerized NEPCs and lignin are important factors of cell wall components of fruits to having a high functionality, and Chinese quince and quince are interesting fruits from this view point.

In vitro binding capacities of three dietary fibers and their mixture for four toxic elements, cholesterol, and bile acid

Water-soluble dietary fibers from apple peels and water-insoluble dietary fibers from wheat bran and soybean-seed hull were used to evaluate their binding capacities for four toxic elements (Pb, Hg, Cd, and As), lard, cholesterol, and bile acids. The water-soluble dietary fibers showed a higher binding capacity for three toxic cations, cholesterol, and sodium cholate; and a lower binding capacity for lard, compared to the water-insoluble ones. A mixture of the dietary fibers from all samples - apple peels, wheat bran, and soybean-seed hull - in the ratio 2:4:4 (w/w) significantly increased the binding capacity of water-insoluble dietary fibers for the three toxic cations, cholesterol, and sodium cholate; moreover, the mixture could lower the concentrations of Pb(2+) and Cd(+) in the tested solutions to levels lower than those occurring in rice and vegetables grown in polluted soils. However, all the tested fibers showed a low binding capacity for the toxic anion, AsO(3)(3-).

Optimization of adsorption of tea polyphenols into oat β-glucan using response surface methodology

Information on interactions between oat β-glucan and tea polyphenols (TP) is not available in the published literatures. Equilibrium dialysis was applied to determine the adsorption of TP into β-glucan, and response surface methodology (RSM) was employed to optimize the absorbing variables (pH, temperature, and phosphate buffered saline (PBS) buffer concentration). The equilibrium data at constant temperature were fitted with the Langmuir, Freundlich, and Redlich-Peterson models. The results showed that the Freundlich model was the best method to describe the experimental data. Parabolic curves were obtained for pH and temperature. In terms of adsorption capacity, factors including temperature, pH/temperature, and buffer concentration/temperature had the greatest influence on the response. The highest adsorption capacity of TP into β-glucan was 134.55 μg mg(-1) at the following optimized conditions: pH 5.56, PBS buffer concentration 0.13 M, and temperature 40 °C. No significant differences (p > 0.05) between the experimental and predicted values confirmed the adequacy of the response surface equations.

Mechanisms underlying the cholesterol-lowering properties of soluble dietary fibre polysaccharides

A number of studies have shown a positive relationship between diets rich in soluble dietary fibres (SDF) such as β-glucan, pectin, guar gum and psyllium, and reduced serum cholesterol and thus a decreased risk of cardiovascular disease (CVD). Three major biological mechanisms have been proposed to explain the cholesterol-reducing effects of SDF: prevention of bile salt (BS) re-absorption from the small intestine leading to an excess faecal BS excretion; reduced glycemic response leading to lower insulin stimulation of hepatic cholesterol synthesis; and physiological effects of fermentation products of SDF, mainly propionate. Evidence for the latter mechanism is inconclusive, whereas in vivo, ex vivo and in vitro experiments suggest that BS micelles "bind" to SDF preventing their re-absorption. Whereas, glycemic responses to SDF have been studied extensively, the nature of interactions between bile salt micelles and SDF that lead to incomplete BS re-absorption are poorly defined. Three potential physicochemical mechanisms are proposed together with suggestions for in vitro experiments to test them.