Metabolism of anthocyanins and their phenolic degradation products by the intestinal microflora

Metabolism of anthocyanins and consequent effects on the gut microbiota

Anthocyanins are natural water-soluble polyphenols present in fruits and vegetables. Health-promoting effects attributed to anthocyanins are mainly associated with oxidative stress inhibition and gut microbiota modulation. Dietary anthocyanins undergo a complex metabolism after ingestion and interact with endogenous and microbial enzymes, leading to the production of a large number of circulating and excreted anthocyanin metabolites and catabolic products. To date, the bioavailability and health benefits of anthocyanins have been widely documented. Although there are several papers that illustrated the metabolism of anthocyanins, the effects of dietary anthocyanins on the modulation of the gut microbial ecology and on the growth of certain microbial species are still poorly understood. The present paper summarizes the recent data on the absorption of anthocyanins in the upper gastrointestine and the metabolism of anthocyanins by gut microbiota. The modulatory effects of anthocyanins from different sources on gut microbiota are also discussed.

Identification of In Vivo Metabolites of Dictamnine in Mice Using HPLC-LTQ-Orbitrap Mass Spectrometry

Dictamnine (4-methoxyfuro[2,3-b]quinolone, DIC), a common furoquinoline alkaloid in the family of Rutaceae, showed diverse biological activities. To investigate the in vivo metabolic pathways of DIC, metabolism of DIC in mice was studied using a high-performance liquid chromatography coupled to electrospray ionization of hybrid linear trap quadrupole orbitrap (HPLC-LTQ-Orbitrap) mass spectrometer. Nine metabolites were identified in the DIC-treated mouse urine, plasma, and fecal samples, of which two were identified as new metabolites. The major metabolic pathways of DIC in animal and human liver microsomes were confirmed in the present study, including o-demethylation, monohydroxylation, N-oxidation, and 2,3-olefinic epoxidation pathways. For the first time, a mono-acetylcysteine conjugate of DIC (M9) was detected from DIC-treated mouse urine and plasma samples, and 4-methoxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid (M10) and 2-(2,8-dihydroxy-4-methoxyquinolin-3-yl)acetaldehyde (M11) were identified as new metabolites of DIC; furthermore, using an in vitro human fecal incubation model, furo[2,3-b]quinolin-4-ol (M1) was verified to be a microbial demethylated metabolite of DIC. Collectively, the present study provided new information on the in vivo metabolic fate of DIC.

Anthocyanin Tissue Bioavailability in Animals: Possible Implications for Human Health. A Systematic Review

Anthocyanins (ACNs) are promising health-enhancing phenolic compounds. We focus on ACN animal tissue bioavailability to provide an evidentiary link between tissue ACNs and their associated health properties. We performed a systematic review of electronic libraries; 279 results were retrieved, and 13 publications met inclusion criteria. Extracted information included animal model employed, administration route, doses, analysis method, and ACN concentration values in tissues. Total ACN concentrations were detected in mice kidney (2.17 × 10⁵ pmol/g), liver (1.73 × 10⁵ pmol/g), heart (3.6 × 10³ pmol/g), and lung (1.16 × 10⁵ pmol/g); and in pig brain (6.08 × 10³ pmol/g). ACNs showed a predominance of parent ACNs in long-term experiments versus an ACN metabolite predominance in short-term experiments. ACNs detected in animal tissues, such as cyanidin-3-glucoside, suggest it may have an important role in human health. This information could be useful to determine proper ACN-intake biomarkers in biological samples in futures studies.

Curcumin as a functional food-derived factor: degradation products, metabolites, bioactivity, and future perspectives

Curcumin is a polyphenol found in turmeric (Curcuma longa), used as a spice, in food coloring, and as a traditional herbal medicine. It has been shown that curcumin has health benefits such as antioxidant, anti-inflammatory, and anticancer properties, improvement of brain function, and control of obesity and diabetes. However, native curcumin easily degrades and has low oral bioavailability, and a recent report has expressed doubt about curcumin's various effects. To overcome its low bioavailability, various curcumin formulations with enhanced bioavailability are currently being developed. This review discusses the chemistry, metabolism, and absorption of curcumin, to which various reported health benefits have been ascribed, as well as curcumin's degradation products and metabolites and their possible functions. Moreover, the research trend towards the obesity- and diabetes-preventing/suppressing aspects of curcumin and the latest case studies on highly water-dispersible and bioavailable curcumin formulations will be discussed. We summarize the challenges concerning research on curcumin's health benefits as follows: clarifying the relationship between curcumin's health benefits and the formation of curcumin-derived oxidation and degradation products and metabolites, determining whether curcumin itself or other components in turmeric are responsible for its effects, and conducting further human trials in which multiple research groups employ the same samples and conditions. High-bioavailability formulations would be useful in such future studies.

Targeted Screening Approach to Systematically Identify the Absorbed Effect Substances of Poria cocos in Vivo Using Ultrahigh Performance Liquid Chromatography Tandem Mass Spectrometry

Poria cocos are extensively used as nutritious food, dietary supplements, and oriental medicine in Asia. However, the effect substances are still not very clear. In this study, a targeted screening approach was developed to systematically identify absorbed constituents of Poria cocos in vivo using ultrahigh performance liquid chromatography tandem mass spectrometry combined with UNIFI software. First, incubation reactions in vitro with rat intestinal microflora and rat liver microsomes were conducted to sum up metabolic rules of main constituents. Second, the absorbed constituents in vivo were picked out and identified based on the results of metabolic study in vitro. Finally, the absorbed active constituents in the treatment of Alzheimer's disease were screened by targeted network pharmacology analysis. A total of 62 absorbed prototypes and 59 metabolites were identified and characterized in dosed plasma. Thirty potential active constituents were screened, and 86 drug-targets shared by absorbed constituents and Alzheimer's disease were discovered by targeted network pharmacology analysis. In general, this proposed targeted strategy comprehensively provides new insight for active ingredients of Poria cocos.

Enhancing the Cancer Cell Growth Inhibitory Effects of Table Grape Anthocyanins

The risk for breast and colon cancer may be lowered in part by high intake of fruits and vegetables. Fruits such as grapes are abundant in bioactive compounds such as anthocyanins. The potential anticancer activity of anthocyanins may be limited by their metabolism in the gut and liver. One metabolic transformation is due to the enzyme catechol-O-methyltransferase (COMT), which methylates polyphenols such as anthocyanins. Entacapone is a clinically used inhibitor of COMT, and has been shown to modulate the methylation of food-derived polyphenols. In this study, we compared the effect of entacapone on the cell viability of colon (Caco-2 and HT-29) and breast (MDA-MB-231) cancer cell lines treated with anthocyanins. Cells were treated with either cyanidin-3-glucoside, delphinidin-3-glucoside, or an anthocyanin-rich grape extract, in the absence or presence of entacapone. Cell viability was assessed using the thiazolyl blue tetrazolium bromide (MTT) assay. Entacapone in combination with the anthocyanins had a greater than additive effect on growth inhibition of the Caco-2 cells. In the MDA-MB-231 cell line, entacapone similarly enhanced the growth inhibitory activity of the anthocyanin extract. Entacapone also had antiproliferative effects when used as a single treatment. Total hydroperoxides was quantified in the cell culture media. Greater concentrations of the treatments resulted in higher levels of total hydroperoxides, indicating that oxidative stress may be an important mechanism for growth inhibition. In conclusion, the antiproliferative activity of fruit-derived anthocyanins was improved in human cancer cell lines by the clinically used drug entacapone. The efficacy and mechanisms of entacapone/anthocyanin combinations should be carefully studied in vivo.

PRACTICAL APPLICATION

Chemical components of grapes are good for our health and have been shown to lower risk for certain cancers. Their beneficial health effects could also be enhanced by consuming other molecules that improve their bioavailability.

BadGluc, a β-glucosidase from Bjerkandera adusta with anthocyanase properties

A glycosidase of the basidiomycete Bjerkandera adusta (BadGluc) was found in screenings to possess a strong decolorizing ability towards malvidin-3-galactoside, an anthocyanin abundant in various berry fruits. The BadGluc was purified from the culture supernatant via FPLC, and the corresponding gene was identified which showed low similarity to other characterized glucosidases. Scanning the primary sequence with PROSITE no active site motif was detected. Eventually, a specific 18 aa consensus pattern was identified manually. The active site motif possessed an undescribed sequence which was only found in a few hypothetical proteins. The corresponding gene was cloned and expressed in Pichia pastoris GS115 yielding activities up to 100 U/L using 4-nitrophenyl-β-d-glucopyranoside (pNPG) as substrate. The enzyme possessed a good temperature (70% after 1 h at 50°C) and pH stability (70% between pH 2 and 7.5), and preferably catalysed the hydrolysis of delphinidin-3-glucoside and cyanidin-3-glucoside, regardless of the position of the terminal Hexa-His tag. This novel glucosidase worked in aqueous solution as well as on pre-stained fabrics making it the first known candidate anthocyanase for applications in the detergent and food industries.

Metabolism and prebiotics activity of anthocyanins from black rice (Oryza sativa L.) in vitro

Anthocyanins are naturally active substances. In this study, anthocyanins from black rice were obtained by membrane filtration and column chromatography separation. Five anthocyanin monomers in black rice extract were identified by HPLC-MS/MS, and the major anthocyanin monomer (cyanidin-3-glucoside, C3G) was purified by preparative HPLC (Pre-HPLC). The proliferative effects of the anthocyanins on Bifidobacteria and Lactobacillus were investigated by determining the media pH, bacterial populations and metabolic products. After anaerobic incubation at 37 °C for 48 h, not only the pH of the media containing C3G was lower than that of the extract of black rice anthocyanin (BRAE), but the numbers of both Bifidobacteria and Lactobacillus were also significantly increased. Furthermore, hydroxyphenylpropionic, hydroxyphenylacetic, and hydroxybenzoic acids and other metabolites were detected by GC-MS in vitro. Our results revealed that the anthocyanins and anthocyanin monomers from black rice had prebiotic activity and they were metabolized into several small molecules by Bifidobacteria and Lactobacillus.

Stability of Anthocyanins and Their Degradation Products from Cabernet Sauvignon Red Wine under Gastrointestinal pH and Temperature Conditions

This study investigated the stability of wine anthocyanins under simulated gastrointestinal pH and temperature conditions, and further studied the evolution of anthocyanin degradation products through simulated digestive conditions. The aim of this study was to investigate the relation between anthocyanins' structure and their digestive stability. Results showed that a total of 22 anthocyanins were identified in wine and most of these anthocyanins remained stable under simulated gastric digestion process. However, a dramatic concentration decrease happened to these anthocyanins during simulated intestinal digestion. The stability of anthocyanins in digestive process appeared to be related to their structure. The methoxy group in the B-ring enhanced the stability of anthocyanins, whereas hydroxyl group resulted in a reduction of their stability. Acylation decreased the stability of malvidin 3-O-glucoside. Pyruvic acid conjugation enhanced the structural stability of pyranoanthocyanins, whereas acetaldehyde attachment weakened their stability. A commercial malvidin 3-O-glucoside standard was used to investigate anthocyanin degradation products under simulated digestion process, and syringic acid, protocatechuic acid and vanillic acid were confirmed to be the degradation products via anthocyanin chalcone conversion path. Gallic acid, protocatechuic acid, vanillic acid, syringic acid, and p-coumaric acid in wine experienced a significant concentration decrease during digestion process. However, wine model solution revealed that phenolic acids remained stable under gastrointestinal conditions, except gallic acid.

Potential interactions among phenolic compounds and probiotics for mutual boosting of their health-promoting properties and food functionalities - A review

Several foods are rich sources of phenolic compounds (PC) and their beneficial effects on human health may be increased through the action of probiotics. Additionally, probiotics may use PC as substrates, increasing their survival and functionality. This review presents available studies on the effects of PC on probiotics, including their physiological functionalities, interactions and capability of surviving during exposure to gastrointestinal conditions and when incorporated into food matrices. Studies have shown that PC can improve the adhesion capacity and survival of probiotics during exposure to conditions that mimic the gastrointestinal tract. There is strong evidence that PC can modulate the composition of the gut microbiota in hosts, improving a variety of biochemical markers and risk factors for chronic diseases. Available literature also indicates that metabolites of PC formed by intestinal microorganisms, including probiotics, exert a variety of benefits on host health. These metabolites are typically more active than parental dietary PC. The presence of PC commonly enhances probiotic survival in different foods. Finally, further clinical studies need to be developed to confirm in vitro and experimental findings concerning the beneficial interactions among different PC and probiotics.

Caco-2 cell transport of purple sweet potato anthocyanins-phospholipids complex

In this study, the role of phospholipids in transepithelial transport and the impact on the antioxidant activity of purple sweet potato anthocyanins (PSPAs) was evaluated. PSPAs were purified by column chromatography, and then PSPAs-phospholipids complex (PSPAs-PC) was prepared. In antioxidant assay in vitro, PSPAs-PC exhibited potential antioxidant activity; meanwhile, it exhibited relatively higher stability in mimic gastrointestinal digestion conditions. The inhibitory effect of PSPAs-PC on the oxidation of soybean oil was significantly higher after 15 days storage. The presence of phospholipids increased the transepithelial transport of PSPAs; its apparent permeability coefficient (Papp) was higher, while its efflux ratio was lower than PSPAs. Based on the above results, it clearly displays the potential of phospholipids in the promotion of intestinal transport of PSPAs, and further studies are needed to explore the in-depth mechanism of the bioavailability promotion effect of phospholipids.

Vanillic acid activates thermogenesis in brown and white adipose tissue

Anthocyanins have a positive effect on resistant obesity; however they cannot usually be absorbed directly but, instead, are metabolized by gut microbiota.

Delphinidin protects colon carcinoma cells against the genotoxic effects of the mycotoxin altertoxin II

Alternaria spp. are ubiquitous molds that are able to produce toxic secondary metabolites which may contaminate food globally. One of those is the mycotoxin altertoxin II (ATX-II), a genotoxic and mutagenic compound. In recent years, different flavonoids that may co-occur with mycotoxins in food were demonstrated to temper toxic effects of molds, mostly through their anti-oxidant properties. Thus, in this study, we assessed the influence of the berry anthocyanidin delphinidin on the toxicity of ATX-II in HT-29 colon carcinoma cells. We performed coupled SRB/WST-1 cytotoxicity assays which revealed only weak antagonistic interactions, and single-cell gel electrophoresis ("comet") assays, where we observed a potent protective effect of delphinidin on the DNA-damaging properties of ATX-II. Furthermore, we investigated the mechanism for this interaction. In the DCF assay delphinidin was found to reduce intracellular oxidative stress levels, which might contribute partly to the latter protection. However, LC-MS experiments showed that co-incubation of the mycotoxin with either delphinidin or its potential degradation product phloroglucinol aldehyde significantly decreased ATX-II concentrations in aqueous solutions, indicating that a direct chemical reaction of ATX-II with these components is likely responsible for the observed loss of toxicity. Our results indicate that delphinidin - and possibly other anthocyanins as well - might play a role in the protection of the gut from Alternaria-induced genotoxicity.

Dietary Anthocyanins and Insulin Resistance: When Food Becomes a Medicine

Insulin resistance is an abnormal physiological state that occurs when insulin from pancreatic β-cells is unable to trigger a signal transduction pathway in target organs such as the liver, muscles and adipose tissues. The loss of insulin sensitivity is generally associated with persistent hyperglycemia (diabetes), hyperinsulinemia, fatty acids and/or lipid dysregulation which are often prevalent under obesity conditions. Hence, insulin sensitizers are one class of drugs currently employed to treat diabetes and associated metabolic disorders. A number of natural products that act through multiple mechanisms have also been identified to enhance insulin sensitivity in target organs. One group of such compounds that gained interest in recent years are the dietary anthocyanins. Data from their in vitro, in vivo and clinical studies are scrutinized in this communication to show their potential health benefit through ameliorating insulin resistance. Specific mechanism of action ranging from targeting specific signal transduction receptors/enzymes to the general antioxidant and anti-inflammatory mechanisms of insulin resistance are presented.

Signatures of anthocyanin metabolites identified in humans inhibit biomarkers of vascular inflammation in human endothelial cells

SCOPE

The physiological relevance of contemporary cell culture studies is often perplexing, given the use of unmetabolized phytochemicals at supraphysiological concentrations. We investigated the activity of physiologically relevant anthocyanin metabolite signatures, derived from a previous pharmacokinetics study of 500 mg 13 C5 -cyanidin-3-glucoside in eight healthy participants, on soluble vascular adhesion molecule-1 (VCAM-1) and interleukin-6 (IL-6) in human endothelial cells.

METHODS AND RESULTS

Signatures of peak metabolites (previously identified at 1, 6, and 24 h post-bolus) were reproduced using pure standards and effects were investigated across concentrations ten-fold lower and higher than observed mean (<5 μM) serum levels. Tumor necrosis factor-α (TNF-α)-stimulated VCAM-1 was reduced in response to all treatments, with maximal effects observed for the 6 and 24 h profiles. Profiles tested at ten-fold below mean serum concentrations (0.19-0.44 μM) remained active. IL-6 was reduced in response to 1, 6, and 24 h profiles, with maximal effects observed for 6 h and 24 h profiles at concentrations above 2 μM. Protein responses were reflected by reductions in VCAM-1 and IL-6 mRNA, however there was no effect on phosphorylated NFκB-p65 expression.

CONCLUSION

Signatures of anthocyanin metabolites following dietary consumption reduce VCAM-1 and IL-6 production, providing evidence of physiologically relevant biological activity.

Navy and black bean supplementation primes the colonic mucosal microenvironment to improve gut health

Common beans (Phaseolus vulgaris L.) are enriched in non-digestible fermentable carbohydrates and phenolic compounds that can modulate the colonic microenvironment (microbiota and host epithelial barrier) to improve gut health. In a comprehensive assessment of the impact of two commonly consumed bean varieties (differing in levels and types of phenolic compounds) within the colonic microenvironment, C57Bl/6 mice were fed diets supplemented with 20% cooked navy bean (NB) or black bean (BB) flours or an isocaloric basal diet control (BD) for 3 weeks. NB and BB similarly altered the fecal microbiota community structure (16S rRNA sequencing) notably by increasing the abundance of carbohydrate fermenting bacteria such as Prevotella, S24-7 and Ruminococcus flavefaciens, which coincided with enhanced short chain fatty acid (SCFA) production (microbial-derived carbohydrate fermentation products) and colonic expression of the SCFA receptors GPR-41/-43/-109a. Both NB and BB enhanced multiple aspects of mucus and epithelial barrier integrity vs. BD including: (i) goblet cell number, crypt mucus content and mucin mRNA expression, (ii) anti-microbial defenses (Reg3γ), (iii) crypt length and epithelial cell proliferation, (iv) apical junctional complex components (occludin, JAM-A, ZO-1 and E-cadherin) mRNA expression and (v) reduced serum endotoxin concentrations. Interestingly, biomarkers of colon barrier integrity (crypt height, mucus content, cell proliferation and goblet cell number) were enhanced in BB vs. NB-fed mice, suggesting added benefits attributable to unique BB components (e.g., phenolics). Overall, NB and BB improved baseline colonic microenvironment function by altering the microbial community structure and activity and promoting colon barrier integrity and function; effects which may prove beneficial in attenuating gut-associated diseases.

Biotransformation and metabolism of three mulberry anthocyanin monomers by rat gut microflora

Anthocyanins (ACNs) are naturally occurring components of human diet. Evidence has accumulated regarding the positive association of their intake with chronic disease. Because microbiota has been considered as a metabolic organ, the bacterial-dependent metabolisms of three types of ACNs from mulberry fruits (cyanidin-3-glucoside (C3G), cyanidin-3-rutinoside (C3R), delphinidin-3-rutinoside (D3R)) during a simulation of large intestine conditions were investigated. ACNs and metabolites were analysed and characterized by high performance liquid chromatography-electrospray ionization-mass spectrum (HPLC-ESI-MS/MS). C3G disappeared after 6h of metabolism, while C3R and D3R were no longer detected after 8h. The metabolism of C3G and C3R mainly resulted in the formation of protocatechuic, vanillic, and p-coumaric acids, as well as 2,4,6-trihydroxybenzaldehyde, while the main metabolites of D3R were gallic acid, syringic acid and 2,4,6-trihydroxybenzaldehyde. This research indicated that the intake of ACNs may result in the appearance of specific metabolites that exert a protective effect in the host physiology.

In vitro approaches to assess the effects of açai (Euterpe oleracea) digestion on polyphenol availability and the subsequent impact on the faecal microbiota

A considerable proportion of dietary plant-polyphenols reach the colon intact; determining the effects of these compounds on colon-health is of interest. We hypothesise that both fibre and plant polyphenols present in açai (Euterpe oleracea) provide prebiotic and anti-genotoxic benefits in the colon. We investigated this hypothesis using a simulated in vitro gastrointestinal digestion of açai pulp, and a subsequent pH-controlled, anaerobic, batch-culture fermentation model reflective of the distal region of the human large intestine. Following in vitro digestion, 49.8% of the total initial polyphenols were available. In mixed-culture fermentations with faecal inoculate, the digested açai pulp precipitated reductions in the numbers of both the Bacteroides-Prevotella spp. and the Clostridium-histolyticum groups, and increased the short-chain fatty acids produced compared to the negative control. The samples retained significant anti-oxidant and anti-genotoxic potential through digestion and fermentation. Dietary intervention studies are needed to prove that consuming açai is beneficial to gut health.

Delphinidin 3-rutinoside-rich blackcurrant extract ameliorates glucose tolerance by increasing the release of glucagon-like peptide-1 secretion

Glucagon‐like peptide‐1 (GLP‐1) is an incretin that is secreted from enteroendocrine L‐cells. Dietary factor‐stimulation of endogenous GLP‐1 is a promising strategy for increasing the action of GLP‐1. Recent studies have shown that berries rich in anthocyanins improve insulin sensitivity and reduce the risk of type 2 diabetes. Our previous study found that the anthocyanin delphinidin 3‐rutinoside (D3R) significantly increases GLP‐1 secretion in GLUTag cells (enteroendocrine L cell line). Blackcurrants are berries that contain high levels of anthocyanins, particularly D3R. Pre‐administered blackcurrant extract (BCE) 5 mg/kg body weight (1 mg D3R/kg) significantly ameliorated glucose tolerance after intraperitoneal glucose injection in rats by stimulating the secretion of GLP‐1 and subsequently inducing insulin secretion. D3R did not break down significantly in the gastrointestinal tract for at least 45−60 min after BCE was administered, suggesting that BCE‐induced GLP‐1 secretion is mainly mediated by D3R and not its degradation products. These findings demonstrate the novel biological function of D3R‐rich BCE as a GLP‐1 secretagogue. An increase in endogenous GLP‐1 secretion induced by BCE may help to reduce the dosages of diabetic medicines and prevent diabetes.

Phenolic Elderberry Extracts, Anthocyanins, Procyanidins, and Metabolites Influence Glucose and Fatty Acid Uptake in Human Skeletal Muscle Cells

Uptake of glucose and fatty acids in skeletal muscle is of interest for type 2 diabetes treatment. The aim was to study glucose and fatty acid uptake in skeletal muscle cells, antioxidant effects, and inhibition of carbohydrate-hydrolyzing enzymes by elderberries. Enhanced glucose and oleic acid uptake in human skeletal muscle cells were observed after treatment with phenolic elderberry extracts, anthocyanins, procyanidins, and their metabolites. The 96% EtOH and the acidified MeOH extracts were highly active. Of the isolated substances, cyanidin-3-glucoside and cyanidin-3-sambubioside showed highest stimulation of uptake. Phloroglucinol aldehyde was most active among the metabolites. Isolated anthocyanins and procyanidins are strong radical scavengers and are good inhibitors of 15-lipoxygenase and moderate inhibitors of xanthine oxidase. As α-amylase and α-glucosidase inhibitors, they are considerably better than the positive control acarbose. The antidiabetic property of elderberry phenolics increases the nutritional value of this plant and indicates potential as functional food against diabetes.

Human intervention study to investigate the intestinal accessibility and bioavailability of anthocyanins from bilberries

We investigated the importance of the large intestine on the bioavailability of anthocyanins from bilberries in humans with/without a colon. Low bioavailability of anthocyanins in plasma and urine was observed in the frame of this study. Anthocyanins reached the circulation mainly as glucuronides. Analysis of ileal effluents (at end of small intestine) demonstrated that 30% of ingested anthocyanins were stable during 8h passage through the upper intestine. Only 20% degradants were formed and mostly intact anthocyanins were absorbed from the small intestine. Higher amounts of degradants than anthocyanins reached the circulation after bilberry extract consumption in both groups of subjects. Comparison of the bioavailability of anthocyanins in healthy subjects versus ileostomists revealed substantially higher amounts of anthocyanins and degradants in the plasma/urine of subjects with an intact gut. The results suggested that the colon is a significant site for absorption of bioactive components such as anthocyanins and their degradation products.

Adherence to a Mediterranean Diet Influences the Fecal Metabolic Profile of Microbial-Derived Phenolics in a Spanish Cohort of Middle-Age and Older People

Despite the evidence regarding the influence of certain polyphenol food sources on the metabolic profile in feces, the association between the different phenolics provided by the diet and the fecal phenolic profile has not been elucidated. In this study, the composition of phenolic metabolites in fecal solutions was analyzed by UPLC-ESI-MS/MS in 74 volunteers. This fecal phenolic profile showed a high interindividual variation of the different compounds analyzed, phenylacetic and phenylpropionic acids being the major classes of phenolic metabolites excreted in feces. Subjects with higher adherence to a Mediterranean dietary pattern presented greater fecal concentrations of benzoic and 3-hydroxyphenylacetic acids, positively correlated with the intake of the principal classes and subclasses of polyphenols and fibers, and higher levels of Clostridium cluster XVIa and Faecalibacterium prausnitzii. These results provide a link among the Mediterranean dietary pattern, the bioactive compounds of the diet, and the fecal metabolic phenolic profile.

Protocatechuic Acid: Inhibition of Fibril Formation, Destabilization of Preformed Fibrils of Amyloid-β and α-Synuclein, and Neuroprotection

Protocatechuic acid (PCA) is the major metabolite of the anthocyanin known as cyanidin 3-glucoside. It is found in plasma and tissues, such as the brain, heart, liver, and kidneys, following consumption of a rich source of this flavonoid. The abnormal pathological assembly of amyloid-β (Aβ) and α-synuclein (αS) is an underlying mechanism involved in the formation of amyloid plaques and Lewy bodies in the brain, which are responsible for neuropathology symptoms in Alzheimer's (AD) and Parkinson's diseases (PD), respectively. This research was performed to evaluate the protective effects of PCA, by establishing its potential role in inhibiting aggregation and fibril destabilization of Aβ and αS proteins. It has been found that PCA inhibits the aggregation of Aβ and αS and destabilizes their preformed fibrils. These results were confirmed by TEM images, electrophoresis, and immunoblotting experiments. Furthermore, PCA prevents the death of PC12 cells triggered by Aβ- and αS-induced toxicity.

Genistein and delphinidin antagonize the genotoxic effects of the mycotoxin alternariol in human colon carcinoma cells

SCOPE

Although associated with anti-oxidative properties, genistein has been reported to induce DNA strand breaks, whereby oxidative stress and topoisomerase poisoning are considered as potential mechanisms. In contrast, delphinidin, a catalytic topoisomerase inhibitor, is known to suppress the DNA-damaging properties of several topoisomerase poisons. Recently, alternariol, a mycotoxin produced by Alternaria spp., was found not only to induce oxidative stress but also to act as a topoisomerase poison. As both, polyphenols and mycotoxins, might occur in our nutrition simultaneously, the question was addressed whether potential combinatory effects on DNA integrity have to be considered.

METHODS AND RESULTS

We determined combinatory effects of either genistein or delphinidin with alternariol in HT-29 cells. Cytotoxicity was assessed by WST-1 and SRB assays, whereby only weak interactions were observed. The comet assay revealed significant antagonistic interactions of both polyphenols with the genotoxicity of AOH. The underlying mechanism comprises the suppression of alternariol-mediated stabilization of DNA/topoisomerase-II-intermediates, as observed in the ICE assay. Furthermore, DEL but not GEN was found to suppress AOH-mediated oxidative stress.

CONCLUSION

Our data indicate that a respective polyphenol-rich diet might aid to protect against genotoxic damages caused by AOH, whereby bioactive concentrations of DEL are predominantly expected locally in the intestines.

Food-based anthocyanin intake and cognitive outcomes in human intervention trials: a systematic review

BACKGROUND

Preclinical evidence suggests that the anthocyanins, which comprise a subclass of dietary flavonoids providing the purple and red pigmentation in plant-based foods, may have a beneficial impact on cognitive outcomes.

METHODS

A systematic review was conducted to identify the published literature on food-based anthocyanin consumption and cognitive outcomes in human intervention trials. The literature search followed PRISMA guidelines and included six databases, as well as additional hand searching.

RESULTS

Seven studies were included in this review, comprising acute trials (n = 4) and longer-term (n = 3) interventions that assessed multiple cognitive outcomes in children, adults and older adults with cognitive impairment. Six of seven studies reported improvements in either a single, or multiple, cognitive outcomes, including verbal learning and memory, after anthocyanin-rich food consumption. As a result of methodological limitations and the large clinical and methodological diversity of the studies, the pooling of data for quantitative analysis was not feasible.

CONCLUSIONS

The impact of food-based anthocyanin consumption on both acute and long-term cognition appears promising. However, adequately powered studies that include sensitive cognitive tasks are needed to confirm these findings and allow the translation of research into dietary messages.

Bilberry extract, its major polyphenolic compounds, and the soy isoflavone genistein antagonize the cytostatic drug erlotinib in human epithelial cells

Erlotinib (Tarceva®) is a chemotherapeutic drug approved for the treatment of pancreatic cancer and non-small cell lung cancer. Its primary mode of action is the inhibition of the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase (RTK). Recently, RTK-inhibiting polyphenols have been reported to interact synergistically with erlotinib. Furthermore some anthocyanidins and anthocyanin-rich berry extracts have been reported to inhibit tyrosine kinases, including the EGFR, which raises the question of potential interactions with erlotinib. Polyphenol-rich preparations such as berry- or soy-based products are commercially available as food supplements. In the present study we tested a bilberry extract, its major anthocyanin and potential intestinal degradation products, as well as genistein, with respect to possible interactions with erlotinib. Cell growth inhibition was assessed using the sulforhodamine B assay, while interactions with EGFR phosphorylation were analyzed by SDS-PAGE/western blotting with subsequent immunodetection. Genistein, bilberry extract, delphinidin-3-O-glucoside and delphinidin were found to antagonize erlotinib whereas phloroglucinol aldehyde was found to enhance cytostatic effects of the drug on human epithelial A431 cells. Genistein also antagonized the EGFR inhibitory effects of erlotinib, whereas bilberry anthocyanins showed no significant interactions in this regard. Our data indicate that different polyphenols are potentially able to impair the cytostatic effect of erlotinib in vitro. Genistein interacts via the modulation of erlotinib-mediated EGFR inhibition whereas bilberry anthocyanins modulated the growth-inhibitory effect of erlotinib without affecting EGFR phosphorylation, thus indicating a different mechanism of interference.

Mulberry anthocyanin biotransformation by intestinal probiotics

This study was designed to evaluate mulberry anthocyanins bioconversion traits for intestinal probiotics. Five intestinal beneficial bacteria were incubated with mulberry anthocyanins under anaerobic conditions at 37°C, and bacterial β-glucosidase activity and anthocyanin level were determined. Results demonstrated that all strains could convert mulberry anthocyanins to some extent. With high β-glucosidase production capacity, Streptococcus thermophiles GIM 1.321 and Lactobacillus plantarum GIM 1.35 degraded mulberry anthocyanins by 46.17% and 43.62%, respectively. Mulberry anthocyanins were mainly biotransformed to chlorogenic acid, crypto-chlorogenic acid, caffeic acid, and ferulic acid during the anaerobic process. Non-enzymatic deglycosylation of anthocyanins also occurred and approximately 19.42% of the anthocyanins were degraded within 48h by this method.

Effects of Black Raspberry Extract and Protocatechuic Acid on Carcinogen-DNA Adducts and Mutagenesis, and Oxidative Stress in Rat and Human Oral Cells

Effects of black raspberry (BRB) extract and protocatechuic acid (PCA) on DNA adduct formation and mutagenesis induced by metabolites of dibenzo[a,l]pyrene (DBP) were investigated in rat oral fibroblasts. The DBP metabolites, (±)-anti-11,12-dihydroxy-11,12,-dihydrodibenzo[a,l]pyrene (DBP-diol) and 11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene (DBPDE) induced dose-dependent DNA adducts and mutations. DBPDE was considerably more potent, whereas the parent compound had no significant effect. Treatment with BRB extract (BRBE) and PCA resulted in reduced DBP-derived DNA adduct levels and reduced mutagenesis induced by DBP-diol, but only BRBE was similarly effective against (DBPDE). BRBE did not directly inactivate DBPDE, but rather induced a cellular response-enhanced DNA repair. When BRBE was added to cells 1 day after the DBP-diol, the BRBE greatly enhanced removal of DBP-derived DNA adducts. As oxidative stress can contribute to several stages of carcinogenesis, BRBE and PCA were investigated for their abilities to reduce oxidative stress in a human leukoplakia cell line by monitoring the redox indicator, 2',7'-dichlorodihydrofluorescein diacetate (H2DCF) in cellular and acellular systems. BRBE effectively inhibited the oxidation, but PCA was only minimally effective against H2DCF. These results taken together provide evidence that BRBE and PCA can inhibit initiation of carcinogenesis by polycyclic aromatic hydrocarbons; and in addition, BRBE reduces oxidative stress. Cancer Prev Res; 9(8); 704-12. ©2016 AACR.

Effects of Montmorency tart cherry (Prunus Cerasus L.) consumption on vascular function in men with early hypertension

BACKGROUND

Tart cherries contain numerous polyphenolic compounds that could potentially improve endothelial function and reduce cardiovascular disease risk.

OBJECTIVE

We sought to examine the acute effects of Montmorency tart cherry (MC) juice on vascular function in subjects with early hypertension.

DESIGN

A placebo-controlled, blinded, crossover, randomized Latin square design study with a washout period of ≥14 d was conducted. Fifteen men with early hypertension [systolic blood pressure (SBP) ≥130 mm Hg, diastolic blood pressure ≥80 mm Hg, or both] received either a 60-mL dose of MC concentrate or placebo. Microvascular reactivity (laser Doppler imaging with iontophoresis), arterial stiffness (pulse wave velocity and analysis), blood pressure, and phenolic acid absorption were assessed at baseline and at 1, 2, 3, 5, and 8 h postconsumption.

RESULTS

MC consumption significantly lowered SBP (P < 0.05) over a period of 3 h, with peak reductions of mean ± SEM 7 ± 3 mm Hg 2 h after MC consumption relative to the placebo. Improvements in cardiovascular disease risk factors were closely linked to increases in circulating protocatechuic and vanillic acid at 1-2 h.

CONCLUSIONS

MC intake acutely reduces SBP in men with early hypertension. These benefits may be mechanistically linked to the actions of circulating phenolic acids. This study provides information on a new application of MCs in health maintenance, particularly in positively modulating SBP. This trial was registered at clinicaltrials.gov as NCT02234648.

Bacterial species involved in the conversion of dietary flavonoids in the human gut

The gut microbiota plays a crucial role in the conversion of dietary flavonoids and thereby affects their health-promoting effects in the human host. The identification of the bacteria involved in intestinal flavonoid conversion has gained increasing interest. This review summarizes available information on the so far identified human intestinal flavonoid-converting bacterial species and strains as well as their enzymes catalyzing the underlying reactions. The majority of described species involved in flavonoid transformation are capable of carrying out the O-deglycosylation of flavonoids. Other bacteria cleave the less common flavonoid-C-glucosides and/or further degrade the aglycones of flavonols, flavanonols, flavones, flavanones, dihydrochalcones, isoflavones and monomeric flavan-3-ols. To increase the currently limited knowledge in this field, identification of flavonoid-converting bacteria should be continued using culture-dependent screening or isolation procedures and molecular approaches based on sequence information of the involved enzymes.

Recent Progress in Anti-Obesity and Anti-Diabetes Effect of Berries

Berries are rich in polyphenols such as anthocyanins. Various favorable functions of berries cannot be explained by their anti-oxidant properties, and thus, berries are now receiving great interest as food ingredients with “beyond antioxidant” functions. In this review, we discuss the potential health benefits of anthocyanin-rich berries, with a focus on prevention and treatment of obesity and diabetes. To better understand the physiological functionality of berries, the exact molecular mechanism of their anti-obesity and anti-diabetes effect should be clarified. Additionally, the relationship of metabolites and degradation products with health benefits derived from anthocyanins needs to be elucidated. The preventive effects of berries and anthocyanin-containing foods on the metabolic syndrome are not always supported by findings of interventional studies in humans, and thus further studies are necessary. Use of standardized diets and conditions by all research groups may address this problem. Berries are tasty foods that are easy to consume, and thus, investigating their health benefits is critical for health promotion and disease prevention.

The Modulatory Effect of Anthocyanins from Purple Sweet Potato on Human Intestinal Microbiota in Vitro

In order to investigate the modulatory effect of purple sweet potato anthocyanins (PSPAs) on human intestinal microbiota, PSPAs were prepared by column chromatography and their influence on intestinal microbiota was analyzed by monitoring the bacterial populations and analyzing short-chain fatty acid (SCFA) concentrations at different time points. The numbers (log10 cell/mL) of Bifidobacterium and Lactobacillus/Enterococcus spp., Bacteroides-Prevotella, Clostridium histolyticum, and total bacteria after 24 h of culture in anaerobic fermentation broth containing PSPAs were 8.44 ± 0.02, 8.30 ± 0.01, 7.80 ± 0.03, 7.60 ± 0.03, and 9.00 ± 0.02, respectively, compared with 8.21 ± 0.03, 8.12 ± 0.02, 7.95 ± 0.02, 7.77 ± 0.02, and 9.01 ± 0.03, respectively, in the controls. The results showed that PSPAs induced the proliferation of Bifidobacterium and Lactobacillus/Enterococcus spp., inhibited the growth of Bacteroides-Prevotella and Clostridium histolyticum, and did not affect the total bacteria number. Total SCFA concentrations in the cultures with PSPAs were significantly higher than in the controls (P < 0.05). Moreover, during the fermentation, the PSPAs were partially fragmented to phenolic acids, which may exert a better effect on intestinal microecology, suggesting that PSPAs may have prebiotic-like activity by generating SCFAs and modulating the intestinal microbiota, contributing to improvements in human health.

The Reciprocal Interactions between Polyphenols and Gut Microbiota and Effects on Bioaccessibility

As of late, polyphenols have increasingly interested the scientific community due to their proposed health benefits. Much of this attention has focused on their bioavailability. Polyphenol-gut microbiota interactions should be considered to understand their biological functions. The dichotomy between the biotransformation of polyphenols into their metabolites by gut microbiota and the modulation of gut microbiota composition by polyphenols contributes to positive health outcomes. Although there are many studies on the in vivo bioavailability of polyphenols, the mutual relationship between polyphenols and gut microbiota is not fully understood. This review focuses on the biotransformation of polyphenols by gut microbiota, modulation of gut microbiota by polyphenols, and the effects of these two-way mutual interactions on polyphenol bioavailability, and ultimately, human health.

Wine and bone health: a review

A light-to-moderate wine consumption has been shown to provide several beneficial effects on the skeletal system, including reduced risk of bone mass loss and fractures. Wine is rich in phenolic compounds, strong phytoestrogens and natural antioxidants, to which bone protection is mainly attributed. The objective of this review was to give an overview of the exact mechanisms by which wine consumption is involved in bone protection. We found a great variety of in vitro research on the beneficial effects of isolated wine phenolics on the skeletal system, with a significant lack of evidence of their in vivo effects. In addition, we found almost no studies investigating how wine, a mixture of these phenolics dissolved in ethanol, affects the skeletal system. Our results warrant further research on this interesting topic.

Dietary Consumption of Black Raspberries or Their Anthocyanin Constituents Alters Innate Immune Cell Trafficking in Esophageal Cancer

Freeze-dried black raspberries (BRB), their component anthocyanins (AC), and a metabolite of BRB ACs, protocatechuic acid (PCA), inhibit the development of esophageal cancer in rats induced by the carcinogen, N-nitrosomethylbenzylamine (NMBA). All three components reduce inflammation in the esophagus and in plasma. The present study determined the relation of changes in inflammatory markers to infiltration of innate immune cells into NMBA-treated esophagus. Rats were injected with NMBA (0.35 mg/kg) for 5 weeks while on control diet. Following NMBA treatment, rats were fed diets containing 6.1% BRB powder, an AC-rich fraction of BRBs (3.8 μmol/g), or 500 ppm PCA. At weeks 15, 25, and 35, inflammatory biomarker expression in the plasma and esophagus was quantified, and infiltration of immune cells in the esophagus was examined. At all three time points, BRB, AC, and PCA similarly affected cytokine production in the esophagus and plasma of NMBA-treated rats, relative to the NMBA-only control. These included decreased expression of the proinflammatory cytokine IL1β and increased expression of the anti-inflammatory cytokine IL10. Moreover, all three diets also increased the expression of IL12, a cytokine that activates both cytolytic natural killer and CD8(+) T cells. In addition, the three diets also decreased infiltration of both macrophages and neutrophils into the esophagus. Overall, our results suggest that another mechanism by which BRBs, ACs, and PCA inhibit NMBA-induced esophageal tumorigenesis is by altering cytokine expression and innate immune cell trafficking into tumor tissues.

Inhibition of pancreatic cancer cell migration by plasma anthocyanins isolated from healthy volunteers receiving an anthocyanin-rich berry juice

PURPOSE

Pancreatic cancer is an aggressive cancer type, of which the most important characteristics are migration and metastasis. Anthocyanins (ACN) are discussed to be protective phytochemicals; however, up to now only scarce data are available regarding their effects on cancer prevention. In this study, we aimed to determine whether ACN and their metabolites from plasma (PAM), isolated from blood of healthy volunteers after ingestion of an ACN-rich juice, are effective in modulating cancer cell migration in vitro.

METHODS

PAM were isolated from blood of healthy volunteers (n = 10) after consumption of an ACN-rich berry juice. Before ingestion (PAM_0min) and after 60 min (PAM_60min), blood was taken and PAM were isolated from plasma by solid-phase extraction. Migration of pancreatic cancer cells PANC-1 and AsPC-1 was assayed in a Boyden chamber. The influence of PAM on cellular reactive oxygen species (ROS) or mitochondria-specific ROS was measured fluorimetrically. mRNA expression levels of matrix metalloproteinases (MMP-2 and MMP-9) and NF-κB mRNA were determined by real-time PCR.

RESULTS

After application of PAM_60min to PANC-1, we observed a reduced cell migration, which was associated with reduced levels of endogenously generated ROS concomitant with reduced NF-κB as well as MMP-2 and MMP-9 mRNA expression levels. In AsPC-1 cells, however, migration was not affected by PAM_60min.

CONCLUSION

It can be assumed that physiologically relevant ACN and their metabolites were able to inhibit pancreatic cancer cell migration in dependency of the phenotype of cells and may thus deserve further attention as potential bioactive phytochemicals in cancer prevention.

Intermolecular binding of blueberry pectin-rich fractions and anthocyanin

Pectin was extracted from blueberry powder into three fractions of water soluble (WSF), chelator soluble (CSF) and sodium carbonate soluble (NSF). The fractions were incubated with cyanidin-3-glucoside (C3G), a mixture of five anthocyanidins (cyanidin, pelargonidin, malvidin, petunidin and delphinidin) or blueberry juice at pH 2.0-4.5. Free anthocyanins and bound anthocyanin-pectin mixtures were separated by ultrafiltration. WSF bound the least amount of anthocyanin at all pH values. CSF had stronger anthocyanin binding ability at pH 2.0-3.6, while NSF had stronger anthocyanin binding ability at pH 3.6-4.5. The pectin and anthocyanin binding was lowest at pH 4.5 and higher at pH 2.0-3.6. Nearly doubling C3G pigment content increased bound anthocyanin percentage by 16-23% at pH 3.6, which favored anthocyanin aromatic stacking, compared to 3-9% increase at pH 2.0. Ionic interaction between anthocyanin flavylium cations and free pectic carboxyl groups, and anthocyanin stacking may be two major mechanisms for pectin and anthocyanin binding.