Characterization of the intestinal transport mechanism of polystyrene microplastics (MPs) and the potential inhibitory effect of green tea extracts on MPs intestinal absorption

The aims of the current study included characterizing the intestinal transport mechanism of polystyrene microplastics (MPs) with different charges and sizes in the intestinal epithelial cell model and determining the inhibitory effect of green tea extracts (GTEs) on the intestinal absorption of MPs in Caco-2 cells. The smaller sizes, which included diameters of 0.2 μm, of amine-modified MPs compared to either larger size (1 μm diameter, or carboxylate-MPs (0.2 and 1 μm diameter) significantly lowered the cell viability of caco-2 cells that were measured by MTT assay (p < 0.05). The transported amount (particles/mL of the cell media) of amine-modified MPs by the Caco-2 cell, was not dependent according to the concentrations, energy, or temperature, but it was higher than the carboxylate-modified MPs. The co-treatment of GTEs with the amine-modified MPs inhibited Caco-2 cell cytotoxicity as well as reduced the production of intracellular reactive oxygen species (ROS) in HepG2 generated by the exposure of amine-modified MPs. The GTEs co-treatment also increased trans-epithelial electrical resistances (TEER) and reduced the transportation of Lucifer Yellow via the Caco-2 monolayer compared to only the amine-modified MPs exposure. The GTEs treatment led to a decrease in the number of amine-modified MPs transported to the basal side of the Caco-2 monolayer. The results from our study suggest that the consumption of GTEs could enhance the intestinal barrier function by recovering intestinal epithelial cell damage induced by MPs, which resulted in a decrease of the intestinal absorption of MPs.

Flavan-3-ol-methylxanthine interactions: Modulation of flavan-3-ol bioavailability in volunteers with a functional colon and an ileostomy

Flavan-3-ols, including the flavan-3-ol monomer (-)-epicatechin, are dietary bioactives known to mediate beneficial cardiovascular effects in humans. Recent studies showed that flavan-3-ols could interact with methylxanthines, evidenced by an increase in flavan-3-ol bioavailability with a concomitant increase in flavan-3-ol intake-mediated vascular effects. This study aimed at elucidating flavan-3-ol-methylxanthine interactions in humans in vivo by evaluating the specific contributions of theobromine and caffeine on flavan-3-ol bioavailability. In ileostomists, the effect of methylxanthines on the efflux of flavan-3-ol metabolites in the small intestine was assessed, a parameter important to an understanding of the pharmacokinetics of flavan-3-ols in humans. In a randomized, controlled, triple cross-over study in volunteers with a functional colon (n = 10), co-ingestion of flavan-3-ols and cocoa methylxanthines, mainly represented by theobromine, increased peak circulatory levels (C_max) of flavan-3-ols metabolites (+21 ± 8%; p < 0.05). Conversely, caffeine did not mediate a statistically significant effect on flavan-3-ol bioavailability (C_max = +10 ± 8%, p = n.s.). In a subsequent randomized, controlled, double cross-over study in ileostomists (n = 10), cocoa methylxanthines did not affect circulatory levels of flavan-3-ol metabolites, suggesting potential differences in flavan-3-ol bioavailability compared to volunteers with a functional colon. The main metabolite in ileal fluid was (-)-epicatechin-3'-sulfate, however, no differences in flavan-3-ol metabolites in ileal fluid were observed after flavan-3-ol intake with and without cocoa methylxanthines. Taken together, these results demonstrate a differential effect of caffeine and theobromine in modulating flavan-3-ol bioavailability when these bioactives are co-ingested. These findings should be considered when comparing the effects mediated by the intake of flavan-3-ol-containing foods and beverages and the amount and type of methylxanthines present in the ingested matrixes. Ultimately, these insights will be of value to further optimize current dietary recommendations for flavan-3-ol intake. CLINICAL TRIAL REGISTRATION NUMBER: This work was registered at clinicaltrials.gov as NCT03526107 (study part 1, volunteers with functional colon) and NCT03765606 (study part 2, volunteers with an ileostomy).

A review of recent progress in improving the bioavailability of nutraceutical-loaded emulsions after oral intake

Increasing awareness of the health benefits of specific constituents in fruits, vegetables, cereals, and other whole foods has sparked a broader interest in the potential health benefits of nutraceuticals. Many nutraceuticals are hydrophobic substances, which means they must be encapsulated in colloidal delivery systems. Oil-in-water emulsions are one of the most widely used delivery systems for improving the bioavailability and bioactivity of these nutraceuticals. The composition and structure of emulsions can be designed to improve the water dispersibility, physicochemical stability, and bioavailability of the encapsulated nutraceuticals. The nature of the emulsion used influences the interfacial area and properties of the nutraceutical-loaded oil droplets in the gastrointestinal tract, which influences their digestion, as well as the bioaccessibility, metabolism, and absorption of the nutraceuticals. In this article, we review recent in vitro and in vivo studies on the utilization of emulsions to improve the bioavailability of nutraceuticals. The findings from this review should facilitate the design of more efficacious nutraceutical-loaded emulsions with increased bioactivity.

( -)-Epicatechin and cardiometabolic risk factors: a focus on potential mechanisms of action

This review summarizes experimental evidence on the beneficial effects of ( -)-epicatechin (EC) attenuating major cardiometabolic risk factors, i.e., dyslipidemias, obesity (adipose tissue dysfunction), hyperglycemia (insulin resistance), and hypertension (endothelial dysfunction). Studies in humans are revised and complemented with experiments in animal models, and cultured cells, aiming to understand the molecular mechanisms involved in EC-mediated effects. Firstly, an assessment of EC metabolism gives relevance to both conjugated-EC metabolites product of host metabolism and microbiota-derived species. Integration and analysis of results stress the maintenance of redox homeostasis and mitigation of inflammation as relevant processes associated with cardiometabolic diseases. In these processes, EC appears having significant effects regulating NADPH oxidase (NOX)-dependent oxidant production, nitric oxide (NO) production, and energy homeostasis (mitochondrial biogenesis and function). The potential participation of cell membranes and membrane-bound receptors is also discussed in terms of direct molecular action of EC and EC metabolites reaching cells and tissues.

Synthesis and Characterization of a (-)-Epicatechin and Barbituric Acid Cocrystal: Single-Crystal X-ray Diffraction and Vibrational Spectroscopic Studies

The paper presents the contribution of the cocrystallization method in the physicochemical modification of catechins that exhibit low oral bioavailability. This was done to obtain cocrystals for two naturally occurring polyphenolic diastereoisomers (+)-catechin and (-)-epicatechin with commonly used coformers. Due to distinct crystallization behavior, only the (-)-epicatechin cocrystal with barbituric acid in a 1:1 stoichiometry was obtained. The cocrystal of (-)-epicatechin (EC) with barbituric acid (BTA) was prepared by the slow solvent-evaporation technique. The structure and intermolecular interactions were determined by X-ray crystallographic techniques. The analysis of packing and interactions in the crystal lattice revealed that molecules in the target cocrystal were packed into tapes, formed by the O-H···O type contacts between the (-)-epicatechin and coformer molecules. The EC molecules interact with the carboxyl group in the BTA coformer mainly by -OH groups from the benzene ring A. The cocrystalline phase constituents were also investigated in terms of Hirshfeld surfaces. The application of Raman spectroscopy confirmed the involvement of the C=O group in the formation of hydrogen bonds between the (-)-epicatechin and barbituric acid molecules. Additionally, the solubility studies of pure EC and the EC-BTA cocrystal exhibited minor enhancement of EC solubility in the buffer solution, and pH measurements confirmed a stable level of solubility for EC and its cocrystal.

Stability and Fermentability of Green Tea Flavonols in In-Vitro-Simulated Gastrointestinal Digestion and Human Fecal Fermentation

Flavonols, the second most abundant flavonoids in green tea, exist mainly in the form of glycosides. Flavonols are known to have a variety of beneficial health effects; however, limited information is available on their fate in the digestive system. We investigated the digestive stability of flavonol aglycones and glycosides from green tea under simulated digestion and anaerobic human fecal fermentation. Green tea fractions rich in flavonol glycosides and aglycones, termed flavonol-glycoside-rich fraction (FLG) and flavonol-aglycone-rich fraction (FLA) hereafter, were obtained after treatment with cellulase and tannase, respectively. Kaempferol and its glycosides were found to be more stable in simulated gastric and intestinal fluids than the derivatives of quercetin and myricetin. Anaerobic human fecal fermentation with FLG and FLA increased the populations of Lactobacilli spp. and Bifidobacteria spp. and generated various organic acids, such as acetate, butyrate, propionate, and lactate, among which butyrate was produced in the highest amount. Our findings indicate that some stable polyphenols have higher bioaccessibilities in the gastrointestinal tract and that their health-modulating effects result from their interactions with microbes in the gut.

A critical review on grape polyphenols for neuroprotection: Strategies to enhance bioefficacy

The aging of populations worldwide is driving greater demands for dietary polyphenols which have been recognized as promising prophylactic and/or therapeutic agents in the context of neurodegeneration, and are ubiquitously present in plant-based diets. In particular, grape-derived products encompass a wide array of phenolic compounds purported with multiple health benefits including neuroprotective efficacy. Despite the increasing preclinical and clinical evidence demonstrating high potential of grape polyphenol (GPP)-rich botanicals in preventing and attenuating diverse neurodegenerative disorders, the limited bioavailability of GPPs, especially in the brain, generates questions as to their applications and effectiveness in neuroprotection. To address this issue, significant research efforts have been made to enhance oral bioavailability of GPPs via application of novel strategies. This review highlights some critical issues related to the bioavailability and neuroprotective efficacy of GPPs and GPP-rich botanicals. The representative bioavailability-enhancing strategies are critically reviewed to provide practical solutions for augmenting the bioefficacy of GPP-rich botanicals. Synergistic applications of encapsulation techniques (for physiochemical protection and bypassing xenobiotic metabolism) and dietary intervention strategies involving modulation of gut microbiota (for generating more bioavailable phenolic metabolites) appear promising, and may substantially enhance the bioefficacy, especially the neuroprotective efficacy, of orally consumed GPPs.

Quercetin and fisetin enhanced the small intestine cellular uptake and plasma levels of epi-catechins in in vitro and in vivo models

Quercetin and fisetin, known as catechol-containing flavonoids, could positively affect the absorption of catechins due to their strong affinity for catechol-O-methyl transferase (COMT), which can methylate and cause the excretion of catechins. The current study examined the effect of quercetin and fisetin on the absorption of epi-catechins (ECs) by using a Caco-2 cell line and an in vivo model. The intestinal transport of total catechins by Caco-2 cells was enhanced from 1.3- to 1.6-fold and 1.4- to 1.7-fold by adding quercetin and fisetin, respectively, compared to the control. It was even higher in the treatment with a mixture of quercetin and fisetin. While EC had the highest value of intestinal transport (169% of the control) in 10% quercetin treatment, EGC (235%), EGCG (244%), and ECG (242%) were significantly transported in the treatment with a 5% mixture of quercetin and fisetin (p < 0.05). In an in vivo pharmacokinetic study, the values of the area under the plasma concentration-time curve (AUC, ng h mL^-1) were also higher in rats orally administered EGCG with 10% quercetin (365.5 ± 25.5) or 10% fisetin (825.3 ± 46.7) than in those administered EGCG only (111.3 ± 13.1). Methylated quercetin and methylated fisetin were determined to be m/z 317.24 and m/z 301.25 [M + H]⁺ with their own product ions, respectively. The results indicate that quercetin or fisetin is superior to ECs for methylation by COMT.

Differentiated Caco-2 cell monolayers exhibit adaptation in the transport and metabolism of flavan-3-ols with chronic exposure to both isolated flavan-3-ols and enriched extracts

Chronic exposure to commonly consumed flavonoids changes their transport and metabolism in a small intestinal cell model.

Natural Agents Used in Chemoprevention of Aerodigestive and GI Cancers

Aerodigestive cancers are on an increasing level in both occurrence and mortality. A major cause in many of these cancers is disruption of the inflammatory pathway, leading to increased cell proliferation, and epigenetic silencing of normal regulatory genes. Here we review the research on several natural products: silibinin, silymarin, quercetin, neem & nimbolide, gingerol, epigallatecatechin-3- gallate, curcumin, genistein and resveratrol conducted on aerodigestive cancers. These types of cancers are primarily those from oral cavity, esophagus/windpipe, stomach, small and large intestine, colon/rectum and bile/pancreas tissues. We report on the utilization in vivo and in vitro systems to research these dose effects on the inflammatory and epigenetic pathway components within the aerodigestive cancer. To follow up on the basic research we will discuss remaining research questions and future directions involving these natural products as putative stand alone or in combination with clinical agents.

Glyceollin Effects on MRP2 and BCRP in Caco-2 Cells, and Implications for Metabolic and Transport Interactions

Glyceollins are phytoalexins produced in soybeans under stressful growth conditions. On the basis of prior evaluations, they show potential to treat multiple diseases, including certain cancers, Type 2 diabetes, and cardiovascular conditions. The aim of the present study was to expand on recent studies designed to initially characterize the intestinal disposition of glyceollins. Specifically, studies were undertaken in Caco-2 cells to evaluate glyceollins' effects on apical efflux transporters, namely, MRP2 and BCRP, which are the locus of several intestinal drug-drug and drug-food interactions. 5- (and 6)-carboxy-2',7'-dichloroflourescein (CDF) was used to provide a readout on MRP2 activity, whereas BODIPY-prazosin provided an indication of BCRP alteration. Glyceollins were shown to reverse MRP2-mediated CDF transport asymmetry in a concentration-dependent manner, with activity similar to the MRP2 inhibitor, MK-571. Likewise, they demonstrated concentration-dependent inhibition of BCRP-mediated efflux of BODIPY-prazosin with a potency similar to that of Ko143. Glyceollin did not appreciably alter MRP2 or BCRP expression following 24 h of continuous exposure. The possibility that glyceollin mediated inhibition of genistein metabolite efflux by either transporter was evaluated. However, results demonstrated an interaction at the level of glyceollin inhibition of genistein metabolism rather than inhibition of metabolite transport.

Dietary Polyphenols as Potential Remedy for Dementia

With increasing life expectancy as a result of better quality of life and improved health care, the incidence of aging related diseases and disorders is heading toward epidemic proportions. Dementia, a spectrum of neurological diseases associated with aging, is an increasingly prevalent disease. No cure exists yet for dementia; however, there are many potential candidates for treatment of dementia that merit more exploration. Polyphenols, which constitute one such class of compounds, are dietary agents that are globally found in commonly consumed food. Many processes that are associated with the pathophysiology of dementia can be modulated by polyphenols. Polyphenolic compounds can alleviate oxidative stress by acting as direct scavengers of free radicals and clearing superoxide and hydroxyl radicals and by increasing the level of antioxidant enzymes such as glutathione peroxidase. They also chelate metal ions to prevent free radical formation. Polyphenols can also combat inflammation by affecting transcription factors such as NF-κB. Some polyphenols may have the potential to inhibit excitotoxicity by regulating intracellular calcium ion concentration, inhibiting glutamate receptors and increasing glutamate reuptake at the synapse. The cognitive decline in dementia due to decreased availability of acetylcholine can also be countered by polyphenols that inhibit acetyl-cholinesterase activity. Taken together, these findings suggest that increasing the consumption of polyphenol rich food may alleviate the effects of dementia. Moreover, their effects on controlling multiple mechanisms that are associated with dementia may also prevent or slow down the onset and progress of this devastating disease.