Digestion property and synergistic effect on biological activity of purple rice (Oryza sativa L.) anthocyanins subjected to a simulated gastrointestinal digestion in vitro

Anthocyanins, a group of polyphenolic pigments, have been proved to possess various bioactivities. However, they are unstable in the small intestine and absorbed with low bioavailability. The discrepancy between the low bioavailability of anthocyanins and their good bioactivities has not been illuminated yet. Moreover, information about the digested property and stability of purple rice anthocyanins in the alimentary tract is still limited. Thus, the present work was designed to study the digestion property and the changes in antioxidant and cytoprotective activities of purple rice anthocyanins using an in vitro digestion model, and to investigate the interactions between gastric and intestinal digested anthocyanins. The results showed that anthocyanins amount and antioxidant and cytoprotective effects didn't change significantly during gastric digestion. However, about 76% of total anthocyanins were degraded during intestinal digestion. The IC₅₀ values of intestinal digested sample tested by DPPH and ABTS methods were about 19.1 and 16.9 μg/mL, respectively, far higher than that of non-digested sample (about 7.7 and 7.1 μg/mL, respectively). Cytoprotective effect of intestinal digested sample also decreased significantly. Synergistic effects on antioxidant and cytoprotective activities were observed between the gastric and intestinal digested samples at a relative low concentration. Those results suggest that the bioactivities of purple rice anthocyanins may be changed after digestion and enhanced through the synergies between their gastric and intestinal digested catabolites.     

Effect of in vitro‐simulated gastrointestinal digestion on the stability and antioxidant activity of blueberry polyphenols and their cellular antioxidant activity towards HepG2 cells

In this study we investigated the influence of in vitro‐simulated gastrointestinal digestion on the bioaccessibility and antioxidant activity of polyphenols from blueberries (Vaccinium spp.). Total phenolic, anthocyanin, and flavonoid content was determined, and extract and digesta compositions were analysed by HPLC‐ESI‐MS/MS. The phenolic compounds were relatively stable under a gastric environment, whereas polyphenols and anthocyanins were unstable under an intestinal environment. The bioaccessibility of polyphenol, anthocyanin, and flavonoid was greatly decreased after the intestinal digestion, and the recoveries were only 13.93%, 1.95%, and 15.68% (the IN sample), respectively. Polyphenolic profile alteration occurred during in vitro‐simulated gastrointestinal digestion. Changes of phenolic compound antioxidant activity during digestion correlated with polyphenol, flavonoid, and caffeic acid concentrations. Digested extract cellular antioxidant activity was lower than non‐digested extract activity (P < 0.05). Polyphenol dose–response correlations with cellular antioxidant activity were observed. These results indicated that in vitro‐simulated gastrointestinal digestion significantly impact polyphenols and their antioxidant activity.     

Phenolic contents,antioxidant activities and potential bioaccessibilities of industrial pomegranate nectar processing wastes

Antioxidant potential and bioaccessibility of co‐products from industrial pasteurised pomegranate nectar (PN) processing such as peel (PP), press cake (PC) and precipitate after clarification (PAC) in comparison with raw material (arils) and final products (CON and PN) were determined. Total phenolic (TPC), flavonoid (TFC), anthocyanin (TAC), tannin contents (TTC) and antioxidant activity (TAA) were determined besides identifying major phenolics and investigating in vitro bioaccessibility after gastrointestinal (GI) digestion. PP showed the highest values, except for TAC. Phenolics (12.7–43.0%) were found to be more stable than anthocyanins (0.6–2.1%) after in vitro GI digestion. PAC was found to be a better source for anthocyanins than CON and also showed higher phenolic bioaccessibility (28.8%) than PN (19.6%). PC and PAC possessed as much TPC, TFC, TTC and TAA levels as CON, with some exceptions. Therefore, these results indicated that not only PP but also PC and PAC should be valorised as a good source for phenolics and anthocyanins.     

In vitro digestibility of phenolic compounds from edible fruits: could it be explained by chemometrics?

The health benefits of phenolic compounds depend on the ingested amount, molecular diversity and gastrointestinal digestibility. The phenolic profile of eight fruits (blackberry, blueberry, strawberry, raspberry, mulberry, pomegranate, green and red globe grapes) was chemometrically associated with their in vitro digestibility (oral, gastric, intestinal). Extractable phenols, flavonoids and anthocyanins strongly correlated with each other (r ≥ 0.84), proanthocyanidins with anthocyanins (r = 0.62) and hydrolysable phenols with both extractable phenols (r = 0.45) and proanthocyanidins (r = ?0.54). Two principal components explained 93% of the variance [61% (free‐phenols), 32% (bounded‐phenols)], and four clusters were confirmed by hierarchical analysis, based in their phenolic richness (CLT 1‐4: low to high) and molecular diversity. In vitro digestibility of extractable phenols and flavonoids was blackberry (CLT‐4)> raspberry (CLT‐2)> red grape (CLT‐1) related to their phenolic richness (r ≥ 0.96; P < 0.001), but anthocyanins’ digestibility was pH‐dependent. Chemometrics is useful to predict the in vitro digestibility of phenolic compounds in the assayed fruits.     

Dried fruits: phytochemicals and their fate during in vitro digestion

Mediterranean dried fruits that are cultivated and produced in Greece; that is, Corinthian currants, figs, prunes, cherries, apricots and peaches were evaluated in terms of total polar phenols, individual simple phenolics, anthocyanins and antioxidant capacity in vitro. The potential release of dried fruit polar phenols among the different fractions of an in vitro digestion model was also determined. Total polar phenol, flavanol, flavone/flavonol content and antioxidant capacity was in the range 86–551 mg GAE/100g, 0.2–57 mg CE/100g, 9–71 mg RE/100g and 6–47 mg AAE/100g, respectively. A 12–82% release of total phenolics was observed post-mastication, which further increased post-gastric digestion. The same trend was also followed in the case of total flavanols and flavones/flavonols. Total polar phenols and flavones/flavonols were found to enter the simulated epithelial cell wall. Simple polar phenolics and anthocyanins were identified and quantified in all dried fruit extracts and in some of the digestion fractions.     

Changes in the phenolic contents and antioxidant activities of citrus peels from different cultivars after in vitro digestion

The aim of this study was to investigate the effects of in vitro digestion on the phenolic contents and antioxidant activities of citrus peels. Three different varieties of citrus peels (mandarin, ponkan and red tangerine) were treated with simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The results showed that the SGF or SIF treatments of the citrus peels did not significantly increase the total phenolic content (TPC) or total flavonoid content (TFC), except for that of the TFC of ponkan peel treated with SGF. However, simulated in vitro digestion did improve the antioxidant activities measured with FRAP and ABTS methods. The effect of SGF was more positive than those of SIF for the FRAP assay, but the opposite was true for ABTS. Notably, both simulated digestion techniques decreased the DPPH free radical scavenging abilities. Simulated digestion in vitro changed the antioxidant activities of the citrus peels.     

Cooking does not impair the impact of pulsed electric field on the protein digestion of venison (Cervus elaphus) during in vitro gastrointestinal digestion

The present study was conducted to elucidate whether cooking impairs the positive effect of pulsed electric field (PEF) on the digestibility of venison during in vitro gastrointestinal protein digestion. Previous studies have used fresh uncooked meat to demonstrate the effect of PEF on protein digestibility during gastrointestinal digestion neglecting the effect that cooking could induce during meat preparation process. PEF-treated samples (T₁, 10 kV, 90 Hz, 20 µs) were cooked (core temperature of 75 °C) and subjected to in vitro simulated gastrointestinal protein digestion along with non-treated controls. A 3% increase of in vitro protein digestibility was found in cooked PEF-treated venison (P < 0.05). A positive (P < 0.05) impact of PEF processing was observed on overall protein digestion as measured by soluble protein (%) and SDS-PAGE. PEF did not change (P > 0.05) the release of minerals from cooked venison during digestion. Cooking had no negative influence on the mechanism through which PEF operates in improving the protein digestibility of venison.     

Stability of antioxidant peptides from duck meat after post‐mortem ageing

The stability of antioxidant peptides from aged duck meat during processing and simulated gastrointestinal digestion was investigated. The antioxidant peptides preserved a high stability in the presence of diverse NaCl or upon various time heating. The antioxidant activities were strengthened by the addition of 4–8% glucose or by heating at 100 °C, whereas they were lost under alkaline conditions. During in vitro digestion, the antioxidant activities increased with pepsin treatment but then decreased following trypsin digestion. Pepsin hydrolysed peptides into short fragments and results in the increased exposure of internal hydrophobic amino acids. With further treatment by trypsin, peptides can be hydrolysed completely and more free amino acids were released, leading to the decline in surface hydrophobicity. These variations might be responsible for the change in antioxidant activity during in vitro digestion. The antioxidant peptides from aged duck with high stability can be used as functional food ingredients to improve human health.     

Advances in the in vitro digestion and fermentation of polysaccharides

In vitro digestion models are widely used to study the structural changes, digestion and release of food components under simulated gastrointestinal conditions. As compared to the in vivo digestion tests, the in vitro digestion reflects the digestion and utilisation of food after ingestion and has the advantages of being time consuming, inexpensive, reproducible and free from moral and ethical restrictions. This study reviewed the current research studies on the in vitro simulated digestion of polysaccharides conducted in the last 5 years and focused on the oral, gastric and intestinal digestion models, with the aim of providing a basis for the further testing of changes in the content, structure and active ingredients of polysaccharides before and after digestion.     

Stabilization of grape skin anthocyanins by copigmentation with enzymatically modified isoquercitrin (EMIQ) as a copigment

The thermal and light stability of grape skin anthocyanins with enzymatically modified isoquercitrin (EMIQ) as a copigment was investigated at different pH levels of 3, 4 and 5. The ratios of anthocyanins to EMIQ were 2:1, 1:1, and 1:2 (w/w), respectively, in the thermal experiments at 90 °C, and EMIQ concentrations (0.25, 0.5, and 1%, w/w) were evaluated respectively in the light experiments. Results revealed that the degradation of anthocyanins copigmented with EMIQ followed first-order reaction kinetics. The half life of anthocyanins extended significantly with the increase of EMIQ concentration (p < 0.05), moreover, the color stability increased due to the addition of EMIQ as the total color difference values ΔE* were smaller for the copigmented anthocyanins. The magnitude of the bathochromic (λ_max) shifted to the longest wavelength absorption band with the increasing copigment concentration for all pH levels. Results demonstrated that EMIQ was an effective copigment to stabilize grape skin anthocyanins.     

Chemical profiles of heated perilla meal extracts and their antioxidant activities

Chemical profiles of aqueous or ethanolic extracts of 140, 170 and 200 °C-heated perilla meal were identified by GC-MS, and antioxidant properties of the extracts were observed via in vitro assays and in bulk oil or oil-in-water (O/W) emulsion. A total of 22 and 27 chemicals were found in aqueous and ethanolic extracts from non-heated samples, respectively. As the heating temperature increased to 200 °C, the carbohydrate and derivative contents decreased significantly (P < 0.05), whereas rosmarinic acid concentration decreased in both extracts. Ethanolic extracts possessed higher antioxidant activities than aqueous extracts based on the results of radical scavenging and ferric-reducing antioxidant power assays and the Rancimat assay, but there were no significant differences among samples (P > 0.05). In the case of O/W emulsions, aqueous extracts inhibited lipid oxidation more efficiently than ethanolic extracts at 50 °C. In particular, heat treatment decreased the antioxidant activities of ethanolic extracts and not aqueous extracts in the O/W emulsion system. Aqueous extracts are recommended in moisture-rich emulsion-based foods while ethanolic extracts are more suitable in a lipid-rich environment for enhancing oxidative stability.     

Physicochemical characterisation and α‐amylase inhibitory activity of tea polysaccharides under simulated salivary,gastric and intestinal conditions

Tea polysaccharides (TPS) are one of the main components of tea with various bioactivities. Digestion could result in the changes of the physicochemical properties and bioactivities of polysaccharides. The objective of this study was to determine the changes in physicochemical properties and α‐amylase inhibitory activities of TPS after simulated digestion. The structure of TPS determined by UV, IR and SEM showed that no obvious changes after salivary digestion, but significant changes after gastrointestinal digestion were observed. After intestinal digestion, the contents of reducing sugar were increased from 0.650 ± 0.011 to 1.594 ± 0.078 mm , and the centre molecular weight was decreased from 540.57 to 375.35 KDa. The molar ratio of monosaccharide was changed after digestion. And α‐amylase inhibition rate was significantly increased (P < 0.05). The results could provide information on the digestibility of TPSin vitro and contribute to the development of related functional foods or medicines.     

Effects of simulated gastrointestinal digestion on the physicochemical properties,erythrocyte haemolysis inhibitory ability and chemical antioxidant activity of mulberry leaf protein and its hydrolysates

Proteins and peptides must be degraded and modified in the gastrointestinal (GI) tract prior to absorption; this process changes their physicochemical and biological properties. Mulberry leaf protein (MP) and its hydrolysates (HMP) have favourable antioxidant activities. To investigate, in vitro and separately, the effects of GI digestion and intestinal digestion on the stability of MP and HMP, we monitored the changes in secondary structures, amino acids, molecular weights and antioxidant activities. We found that MP was more hydrolysed by pepsin than by pancreatin, unlike HMP. The final digests of MP and HMP were mainly composed of polypeptides (0.5–6.5 kDa) and oligopeptides (<0.5 kDa), respectively. The GI digestion influenced MP and HMP differently; GI digestion increased the antioxidant efficiency of MP and decreased that of HMP. For the intestinal digests, the antioxidant activities of MP and HMP also differed. The 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulphonic acid) diammonium salt (ABTS) radical quenching abilities of MP and HMP at 1 mg mL^?1 were comparable to or exceeded that of L‐glutathione (GSH) and 6‐hydroxy‐2,5,7,8‐tetramethychroman‐2‐carboxylic acid (trolox). Meanwhile, the erythrocyte haemolysis rates of MP, HMP and their GI products at 0.05–1.0 mg mL^?1 were significantly lower than that of the 2,2′‐azobis (isobutyramidine) dihydrochloride (AAPH) control. Both MP and HMP can be used as natural antioxidants and may promote digestive health.     

Solvent extraction and in vitro simulated gastrointestinal digestion of phenolic compounds from purple sweet potato

The total content of phenolic compounds in purple sweet potato (PSP) was determined and the release of such compounds from PSP in gastrointestinal digestion was studied in vitro. The extraction conditions for the maximum recovery of free phenol (FP) and bound phenol (BP) from PSP were determined by response surface methodology (RSM). The maximum recovery of FPPSP was 14.16 ± 0.87 mg GAE per g short for dry weight (DW), which was obtained using 60% (v/v) ethanol maceration with a liquid–solid ratio of 57.21:1 (mL g⁻¹) at 51.93 °C for 2.12 h. The maximum recovery for BPPSP was 7.54 mg GAE per g DW, which was obtained upon hydrolysis with 1.87 mol L⁻¹ NaOH at a liquid–solid ratio of 35.93:1 (mL g⁻¹) for 4.74 h. The maximum phenolic content was released after 1 and 2 h for the in vitro gastric and intestinal digestion respectively. The release of the phenolics was promoted by pepsin and gastric acid during gastric digestion, while it was further promoted by trypsin during intestinal digestion.     

Biochemical and antioxidant properties of peptidic fraction generated from crab (Portunus trituberculatus) shells by enzymatic hydrolysis

The biochemical properties and in vitro antioxidant activity of the crab (Portunus trituberculatus) shell hydrolysates (CSHs) generated by pepsin and protamex hydrolysis were evaluated. The amino acids profile of CSHs showed a high percentage of essential amino acids (>36%). The hydrolysates were mainly composed of low molecular weight peptides (<3 kDa). CSHs showed excellent solubility and possessed interfacial properties, which were governed by their concentrations. The antioxidant activities of CSHs were evaluated using various in vitro antioxidant assays, including the total antioxidant activity, DPPH, hydroxyl and ABTS radical scavenging method and reducing power assay. CSHs exhibited a good antioxidant activity compared to that of ascorbic acid. Results from this study suggested that the peptidic fractions of crab shells were good source of natural antioxidants and peptides with interesting functionalities.     

Simulated gastrointestinal digestion and in vitro colonic fermentation of date (Phoenix dactylifera L.) seed polyphenols

Date seeds are a by‐product of date fruit industry and a rich source of polyphenols. In this study, in vitro bioaccessibility and colonic fermentation of major polyphenols from date seed powder (DSP) and DSP‐fortified yoghurt (DSPY) were investigated using HPLC. Catechin, epicatechin and procyanidin A2, B1 and B2 were stable during simulated gastric and sequential intestinal digestion. Bioaccessibility was significantly (P < 0.05) higher for all compounds from DSPY compared with DSP. After in vitro colonic fermentation of insoluble digestion materials, most of the target compounds were metabolised by faecal bacteria to ferulic acid, 3‐hydroxyphenylacetic acid, 3‐phenylpropionic acid and 3‐(4‐hydroxyphenyl) propionic acid. DSPY contained significantly (P < 0.05) higher level of free polyphenols as indicated by higher bioaccessibility; however, the stability of the polyphenols and their fermentation products from DSPY were similar to that of DSP alone. These data would be useful in product developments incorporating DSP as a source of polyphenols in food products.     

Fermented coconut jelly as a probiotic vehicle,physicochemical and microbiology characterisation during an in vitro digestion

There is little information on the survival of probiotics in plant-based foods after simulated gastric and intestinal conditions, likewise the microstructure arrangement in the no-dairy fermented food. This work aimed to study if the agar–agar in a fermented coconut jelly confers protection to probiotics, phenolic and antioxidant compounds during in vitro digestion. Samples containing higher agar–agar amounts tend to retain (P < 0.05) antioxidant and phenolic compounds in their network better, even after the in vitro digestion. Also, a compact and homogeneous microstructure was observed by the Confocal Laser Scanning Microscopy. The texture profile analysis shows that 1% of agar samples presented the maximum hardness (P < 0.05) due to more bonding points and intermolecular interactions. Finally, the survival of probiotics remained above the recommended values (10⁶–10⁷ CFU g⁻¹) after the in vitro digestion of a product with probiotic potential.     

Metabolic and microbial modulation of phenolic compounds from raspberry leaf extract under in vitro digestion and fermentation

Raspberry leaves, by-products in raspberry production, are also a rich source of bioactive phytochemicals. In this study, the changes of phenolic compounds in raspberries leaf extract (RLE) under in vitro digestion and colonic fermentation were further studied by HPLC-MS analysis and 16S rRNA. The results showed that the phenolic compounds in RLE were relatively stable during in vitro gastric digestion; however, in the subsequent intestinal digestion and colonic fermentation, their content decreased sharply. A large amount of hydroxyphenylpropionic acid, hydroxyphenylacetic acid and urolithins were produced under the action of gut microbiota. Moreover, compared with corresponding control, RLE significantly reduced the ratio of Firmicutes/Bacteroidetes in all volunteers, increased the relative abundances of some beneficial bacteria, Enterococcus, Prevotella, and decreased the relative abundances of potential pathogens, Clostridium and Faecalibacterium. These findings suggest that RLE during in vitro digestion and fermentation has positive effects on gut microbiota and potential value of maintaining intestinal health.     

In vitro bioaccessibility of ergocalciferol in nanoemulsion‐based delivery system: the influence of food‐grade emulsifiers with different stabilising mechanisms

The effect of emulsifier type on the in vitro bioaccessibility of ergocalciferol‐loaded nanoemulsions was examined (mouth, stomach and small intestinal phases). Oil‐in‐water nanoemulsions were prepared using emulsifiers with different stabilising mechanisms: decaglycerol monooleate (MO7S; steric), modified lecithin (ML; electrostatic), sodium caseinate (SC; electrosteric) and ML‐MO7S (combined electrostatic and steric). The droplet size, size distribution, ζ‐potential and microstructure of nanoemulsions during digestion depended on the emulsifier type. The fate of lipid in the small intestinal phase also relied on the emulsifier type, with the free fatty acids release rate decreasing in the following order: MO7S > ML‐MO7S > ML > SC. The ergocalciferol bioaccessibilities in nanoemulsions prepared using MO7S (62%), ML (64%) and ML‐MO7S (65%) were similar and significantly higher than that stabilised by SC (12%). No significant loss of ergocalciferol was observed in all nanoemulsions after full digestion; they were chemically stable against digestion conditions, regardless of the emulsifier type.     

In vitro bioaccessibility of avenanthramides in cookies made with malted oat flours

This study evaluated the effects of malting and in vitro digestion on the bioaccessibility of six avenanthramides (AVNs), soluble phenols (SPs) and antioxidant capacity (ORAC) in cookies (3B, 4B, 5B) prepared with oat flour malted for three (M3), four (M4), five (M5) days, respectively. Control cookies (CTRL) were made with non-malted oat flour (M0). Five-days malting increased the AVN content of native kernels up to 10-folds, whereas SPs and ORAC tripled their values. After the in vitro digestion, AVNs showed their bioaccessibility in the following order: 5B > 4B > 3B, with a recovery of 1703 μg AVNs per 50 g portion of 5B cookies, compared to 135 μg of CTRL. Results showed that the inclusion of 27% malted oat flour was effective to formulate functional cookies with satisfactory technological properties, high AVN content and bioaccessibility.