Molecular interactions between cereal soluble dietary fibre polymers and a model bile salt deduced from 13C NMR titration

The fate of mamaku gum in the gut: effect on in vitro gastrointestinal function and colon fermentation by human faecal microbiota

Mamaku is a fern indigenous to the Pacific Islands with a long history of use for therapeutic benefits such as to combat skin conditions and manage gastrointestinal discomfort; however, the scientific understanding is limited. In this study, we examined the effect of mamaku gum, extracted from different age fronds of the New Zealand Black tree fern (Cyathea medullaris, Mamaku) (stage 1: young, stage 2: fully grown and stage 3: old), on gut function using in vitro models of static digestion, enzyme activity and static colonic fermentation. Under simulated gastric and small intestinal conditions, mamaku polysaccharide (MP) was indigestible as there was no decrease in the molecular weight (Mw) of the polymer. Mamaku gum could reduce the activity of digestive enzymes (α-amylase, pepsin and lipase) in a concentration-dependent manner, with the stage 1 sample showing the highest inhibition and stage 3 the lowest. All three mamaku gum samples could also equally bind bile acids during intestinal digestion. During fermentation, human faecal microbiota utilised the mamaku gum and significantly increased the production of total short-chain fatty acids (SCFAs) and reduced the pH when compared with the blank. However, changes in SCFAs and pH for mamaku groups were less prominent than for inulin and guar gum control groups, suggesting lower fermentability of mamaku gum compared to the latter two. Furthermore, mamaku gum altered the composition of colonic microbiota, specifically reducing the ratio of Firmicutes to Bacteroidetes and increasing the relative abundance of Bacteroides, Enterococcus, Paraprevotella and Parabacteroides genera. No obvious difference between mamaku gum samples from stage 1, 2 and 3 was observed during fermentation. Collectively, these results suggest that mamaku gum may modulate the functionality of the host gut by reducing enzyme activity, binding bile acids, altering the colonic microbial composition and producing SCFAs.

Interaction of polymers with bile salts - Impact on solubilisation and absorption of poorly water-soluble drugs

Formulating poorly soluble drugs with polymers in the form of solid dispersions has been widely used for improving drug dissolution. Endogenous surface-active species present in the gut, such as bile salts, lecithin and other phospholipids, have been shown to play a key role in facilitating lipids and poorly soluble drugs solubilisation in the gut. In this study, we examined the possible occurrence of interactions between a model bile salt, sodium taurocholate (NaTC), and model spray dried solid dispersions comprising piroxicam and Hydroxypropyl Methylcellulose (HPMC), a commonly used hydrophilic polymer for solid dispersion preparation. Solubility measurements revealed the good solubilisation effect of NaTC on the crystalline drug, which was enhanced by the addition of HPMC, and further boosted by the drug formulation into solid dispersion. The colloidal behaviour of the solid dispersions upon dissolution in biorelevant media, with and without NaTC, revealed the formation of NaTC-HPMC complexes and other mixed colloidal species. Cellular level drug absorption studies obtained using Caco-2 monolayers confirmed that the combination of drug being delivered by solid dispersion and the presence of bile salt and lecithin significantly contributed to the improved drug absorption. Together with the role of NaTC-HPMC complexes in assisting the drug solubilisation, our results also highlight the complex interplay between bile salts, excipients and drug absorption.

In vitro digestion of designed emulsions based on milk protein and guar gum systems

There is a growing interest in designing novel food microstructures that can control nutrient digestion and provide satiety for tackling obesity. In this study, phase separated microstructures of skimmed milk powder (SMP) and guar gum (GG) were the main focus, and these can be considered as water-in-water (W/W) emulsions. Through the incorporation of oil into these systems, it was possible to form model systems of SMP-GG-OIL, showing the lipid phase within the protein phase within the polysaccharide phase. The in vitro digestibility of such phase separated model systems of SMP-GG-OIL with different microstructures was investigated using a pH stat method. Confocal laser scanning microscopy also revealed structural changes that occurred to the emulsified lipid droplets as they passed through a gastrointestinal (GI) model. The microstructures were created based on the tie-lines on a previously established phase diagram of SMP-GG, and shown to be able to control lipid digestion. For a selected tie-line, the lipolysis follows the order: protein continuous > bi-continuous > polysaccharide continuous system, at a certain level of oil addition. The mechanism involved in the lipolysis of the designed formulations/microstructures was dependent upon the protein, rather than GG, and was driven by the protein concentration. These findings provide insights for potential applications in functional food designing in the food industry.

An Insight into Antihyperlipidemic Effects of Polysaccharides from Natural Resources

Hyperlipidemia is a chronic metabolic disease caused by the abnormal metabolism of lipoproteins in the human body. Its main hazard is to accelerate systemic atherosclerosis, which causes cerebrovascular diseases such as coronary heart disease and thrombosis. At the same time, although the current hypolipidemic drugs have a certain therapeutic effect, they have side effects such as liver damage and digestive tract discomfort. Many kinds of polysaccharides from natural resources possess therapeutic effects on hyperlipidemia but still lack a comprehensive understanding. In this paper, the research progress of natural polysaccharides on reducing blood lipids in recent years is reviewed. The pharmacological mechanisms and targets of natural polysaccharides are mainly introduced. The relationship between structure and hypolipidemic activity is also discussed in detail. This review will help to understand the value of polysaccharides in lowering blood lipids and provide guidance for the development and clinical application of new hypolipidemic drugs.

Fermentation profile, cholesterol-reducing properties and chemopreventive potential of β-glucans from Levilactobacillus brevis and Pediococcus claussenii - a comparative study with β-glucans from different sources

The aim of the present study was to investigate whether β-glucans obtained from the lactic acid bacteria (LAB) Levilactobacillus (L.) brevis and Pediococcus (P.) claussenii exhibit similar physiological effects such as cholesterol-binding capacity (CBC) as the structurally different β-glucans from oat, barley, and yeast as well as curdlan. After in vitro fermentation, fermentation supernatants (FSs) and/or -pellets (FPs) were analyzed regarding the concentrations of short-chain fatty acids (SCFAs), ammonia, bile acids, the relative abundance of bacterial taxa and chemopreventive effects (growth inhibition, apoptosis, genotoxicity) in LT97 colon adenoma cells. Compared to other glucans, the highest CBC was determined for oat β-glucan (65.9 ± 8.8 mg g^-1, p < 0.05). Concentrations of SCFA were increased in FSs of all β-glucans (up to 2.7-fold). The lowest concentrations of ammonia (down to 0.8 ± 0.3 mmol L^-1) and bile acids (2.5-5.2 μg mL^-1) were detected in FSs of the β-glucans from oat, barley, yeast, and curdlan. The various β-glucans differentially modulated the relative abundance of bacteria families and reduced the Firmicutes/Bacteroidetes ratio. Treatment of LT97 cells with the FSs led to a significant dose-dependent growth reduction and increase in caspase-3 activity without exhibiting genotoxic effects. Though the different β-glucans show different fermentation profiles as well as cholesterol- and bile acid-reducing properties, they exhibit comparable chemopreventive effects.

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.

Structurally different mixed linkage β-glucan supplements differentially increase secondary bile acid excretion in hypercholesterolaemic rat faeces

Mixed linkage (1→3),(1→4)-β-d-glucan (BG) is a soluble fibre available from oat and barley grains that has been gaining interest due to its health-promoting role in cardiovascular diseases and its ability to modulate the glycaemic index which is beneficial for people with diabetes. This study investigates the effect of three purified barley BGs, with different molecular weight and block structure, on faecal bile acid excretion in hypercholesterolaemic rats. Wistar rats (48 male) were divided in four groups: Control group fed with the cellulose-rich diet (CON); Glucagel group fed with the commercial BG (GLU, 100 kDa), and rats fed with low molecular weight BG (LBG, 150 kDa) and medium molecular weight BG (MBG, 530 kDa). The bile acid profiles of rat faecal samples were measured using gas chromatography-mass spectrometry (GC-MS). A metabolite profiling approach led to the identification of 7 bile acids and 45 other compounds such as sterols, fatty acids and fatty alcohols. Subsequent application of ANOVA-simultaneous component analysis and Principal Component Analysis revealed that all three BG diets increased bile acid faecal excretion compared to the control group. The bile acid excretion was found to be different in all three BG diets and the MBG group showed a significantly higher level of faecal secondary bile acids, including deoxycholic acid, hyodeoxycholic acid, and lithocholic acid. We hypothesise that the hydrophobic surface of the secondary bile acids, which are known to cause colon cancer, has high affinity to the hydrophobic surfaces of cellulosic blocks of the BG. This in vivo study demonstrates that the molecular weight and/or block structures of BG modulate the excretion of secondary bile acids. This finding suggests that developing diets with designed BGs with an optimal molecular structure to trap carcinogenic bile acids can have a significant impact on counteracting cancer and other lifestyle associated diseases.

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.

Bile acid-retention by native and modified oat and barley β-glucan

Foods rich in cereal β-glucan are efficient dietary tools to help reduce serum cholesterol levels and hence the risk of cardiovascular diseases. However, β-glucan undergoes various reactions during food processing, which alter its viscous properties and interactions with components of the gastrointestinal tract. It has been proposed in the literature that oxidation and partial hydrolysis increase β-glucan's bile acid-binding activity, and therefore its effectiveness in lowering cholesterol. Here, the passage kinetics of a bile salt mix across a dialysis membrane was studied with or without oat and barley β-glucan extracts, native or modified (partial hydrolysis and oxidations by sodium periodate or TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)). Bile acid-retention turned out to be purely a function of viscosity, with the most viscous native extracts exhibiting the strongest retardation of bile acid permeation. Opposite of what was suggested in the literature, oxidation and molecular weight reduction do not seem to increase the bile acid-binding capability of β-glucan.

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.

Retention of Primary Bile Acids by Lupin Cell Wall Polysaccharides Under In Vitro Digestion Conditions

Interference of dietary fibres with the enterohepatic circulation of bile acids is proposed as a mechanism for lowering cholesterol. We investigated how lupin hull and cotyledon dietary fibres interact with primary bile acids using an in vitro model under simulated upper gastrointestinal conditions. Cell wall polysaccharides were isolated and extracted to separate pectin-like, hemicellulosic, and lignocellulosic structures. Lupin hull consisted mainly of structural components rich in cellulose. The viscosity of the in vitro digesta of lupin hull was low, showing predominantly liquid-like viscoelastic properties. On the other hand, lupin cotyledon fibre retarded bile acid release due to increased viscosity of the in vitro digesta, which was linked with high contents of pectic polymers forming an entangled network. Molecular interactions with bile acids were not measured for the hull but for the cotyledon, as follows: A total of 1.29&nbsp;µmol/100&nbsp;mg&nbsp;DM of chenodesoxycholic acids were adsorbed. Molecular interactions of cholic and chenodesoxycholic acids were evident for lignin reference material but did not account for the adsorption of the lupin cotyledon. Furthermore, none of the isolated and fractionated cell wall materials showed a significant adsorptive capacity, thus disproving a major role of lupin cell wall polysaccharides in bile acid adsorption.

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.

Effects of cereal soluble dietary fibres on hydrolysis of p-nitrophenyl laurate by pancreatin

The aim of this study was to investigate the effects of cereal soluble dietary fibres (SDFs), β-glucans (BG) from oat and barley as well as arabinoxylans (AX) from wheat and rye, on the lipolysis of p-nitrophenyl laurate (p-NP laurate). p-NP laurate emulsions were prepared in the presence of increasing concentrations of SDFs (0.1%, 1.0% and 1.5% w/v), and lipolysis of emulsions by pancreatic lipase, particle size distribution of the p-NP laurate droplets, and viscosity of emulsions with soluble dietary fibres were measured. It was found that with increasing viscosity of SDFs, the rate of lipolysis decreased while the initial droplet size of the emulsion increased. Rate coefficients were more consistently correlated with average droplet size than with viscosity, suggesting that SDFs inhibited lipolysis primarily by increasing the size of droplets through flocculation, thereby decreasing the available surface area for lipase action.

Effect of substituent pattern and molecular weight of cellulose ethers on interactions with different bile salts

Some known mechanisms proposed for the reduction of blood cholesterol by dietary fibre are: binding with bile salts in the duodenum and prevention of lipid absorption, which can be partially related with the bile salt binding. In order to gain new insights into the mechanisms of the binding of dietary fibre to bile salts, the goal of this work is to study the main interactions between cellulose derivatives and two types of bile salts. Commercial cellulose ethers: methyl (MC), hydroxypropyl (HPC) and hydroxypropylmethyl cellulose (HPMC), have been chosen as dietary fibre due to their highly functional properties important in manufactured food products. Two types of bile salts: sodium taurocholate (NaTC) and sodium taurodeoxycholate (NaTDC), have been chosen to understand the effect of the bile salt type. Interactions in the bulk have been investigated by means of differential scanning calorimetry (DSC) and linear mechanical spectroscopy. Results show that both bile salts have inhibitory effects on the thermal structuring of cellulose ethers and this depends on the number and type of substitution in the derivatised celluloses, and is not dependent upon molecular weight. Concerning the bile salt type, the more hydrophobic bile salt (NaTDC) has greater effect on these interactions, suggesting more efficient adsorption onto cellulose ethers. These findings may have implications in the digestion of cellulose-stabilised food matrices, providing a springboard to develop new healthy cellulose-based food products with improved functional properties.

Probing interactions between β-glucan and bile salts at atomic detail by ¹H-¹³C NMR assays

Polysaccharides are prospective hosts for the delivery and sequestration of bioactive guest molecules. Polysaccharides of dietary fiber, specifically cereal (1 → 3)(1 → 4)-β-glucans, play a role in lowering the blood plasma cholesterol level in humans. Direct host-guest interactions between β-glucans and conjugated bile salts are among the possible molecular mechanisms explaining the hypocholesterolemic effects of β-glucans. The present study shows that (1)H-(13)C NMR assays on a time scale of minutes detect minute signal changes in both bile salts and β-glucans, thus indicating dynamic interactions between bile salts and β-glucans. Experiments are consistent with stronger interactions at pH 5.3 than at pH 6.5 in this in vitro assay. The changes in bile salt and β-glucan signals suggest a stabilization of bile salt micelles and concomitant conformational changes in β-glucans.

Interactions between cellulose ethers and a bile salt in the control of lipid digestion of lipid-based systems

In order to gain new insights into the potential of specific dietary fibres to control lipid digestion, the goal of this work is to study the main interactions between commercial cellulose ethers, as dietary fibre, and a bile salt, as an important duodenal component present during the digestibility of lipids. These interactions have been evaluated in two different scenarios found for an oil-in-water emulsion on its transit through the duodenum. Namely, interactions in the continuous phase and competitive adsorption at the oil-water interface have been looked at by means of micro-differential scanning calorimetry (micro-DSC) and interfacial tension (IT). Micro-DSC revealed that the presence of the bile salt affects the thermogelation process of cellulose derivatives, suggesting binding to cellulose ethers. The effect on thermogelation seems to be cellulose type-dependent. IT measurements proved the ability of cellulose ethers to compete for the oil-water interface in the presence of the bile salt. Interactions in the bulk might have an impact on this interfacial scenario. These findings may have implications in the digestion of emulsified lipids, hence providing a springboard to develop new cellulose-based food products with improved functional properties.

Physicochemical Study of Bile Salt-Polymer Micellar Aggregates

The micellar behavior of Sodium Deoxycholate (NaDC), a bile salt in presence of a neutral water soluble polymer Poly(vinylpyrrolidone) (PVP) has been investigated at four different temperatures (10–40 ºC) using conductometric, tensiometric, viscometric and fluorometric methods. NaDC is found to associate co-operatively with the polymer beyond a critical concentration, saturate the polymer completely and then undergo micellization at a higher concentration. The counter-ion binding capacity to the micelles is considerably reduced in presence of PVP. The thermodynamic properties of micellization and interfacial adsorption depend on the polymer concentration and the entropic contributions are observed to control the complexation process. The NaDC-PVP aggregate exhibits polyelectrolytic behavior. The aggregation number (N) and polarity index (I1/I3) of the NaDC-PVP mixed entities have been explored by pyrene fluorescence probing technique. The values of N and I1/I3 are found to be affected by [PVP] and temperature: the N values decrease with temperature while those of I1/I3 show increasing trend. The dependence of N and I1/I3 values on [PVP] and temperature reveal interesting insights into the NaDC-PVP complexation phenomenon.

Characterization and antioxidant activity of the complex of tea polyphenols and oat β-glucan

Few data are available about the effects of complexation of polyphenols with polysaccharide on their bioavailability. The complex of tea polyphenols (TP) with oat β-glucan was characterized by ultraviolet-visible spectrometry, Fourier transform infrared spectrometry, differential scanning calorimetry, atomic force microscopy, and solid-state (13)C NMR spectroscopy. The results indicated that the bonds which governed the interaction between TP and oat β-glucan were strong hydrogen bonds. The in vitro antioxidant activity of TP, β-glucan, their complex, and physical mixture was assessed using four systems, namely, DPPH(•), OH(•), and O(2)(•-) scavenging activities and reducing power. The complexation and blending of TP and β-glucan exhibited different impacts on the index of in vitro and in vivo antioxidant capacities. In the concentration range of 0.5-2.5 mg mL(-1), the complex had highest O(2)(•-) scavenging activity, whereas the highest OH(•) scavenging activity was found with the physical mixture. For antioxidant testing in vivo, there was no significant difference between the complex and the physical mixture in terms of glutathione peroxidase activity and levels of malondialdehyde and total antioxidant capacity in serums. However, the complex exhibited much higher activities of superoxide dismutase and glutathione peroxidase in livers than the physical mixture. The present study provided a deeper understanding of the influence of molecular interaction between TP and oat β-glucan on their antioxidant activities.