Bioaccessibility of phenolic compounds in Psidium guajava L. varieties and P. friedrichsthalianum Nied. after gastrointestinal digestion.

Psidium guajava L. and Psidium friedrichsthalianum Nied are part of the Psidium species native to America. Nowadays, it is essential to study the phenolic compound (PC) profile and their changes during digestion and the fractions available for absorption. This study aimed to characterize the PC profile in some Psidium species and their bioaccessibility (BA). Fifty-seven compounds were identified, and forty-six belonged to ten different phenolic classes. PC profiles showed significant differences between the species and the intestinal fraction P. friedrichsthalianum Nied. showed the highest PC content, although it mostly belonged to non-extractable polyphenols. This leads to the lowest BA (37%); P. guajava L. 'Morada' showed the highest (47%). Hydroxycinnamic acids were the most stable PC after gastrointestinal digestion. This study showed relevant differences in the PC content and profile of different Psidium species and changes between the PC in the original matrix and those released in the different stages of gastrointestinal digestion.

Instant Controlled Pressure Drop as a Strategy To Modify Extractable and Non-extractable Phenolic Compounds: A Study in Different Grape Pomace Materials.

Instant controlled pressure drop (DIC) is a technology able to modify the polyphenol profile in vegetal materials. However, information about how polyphenols are transformed, particularly regarding non-extractable polyphenol (NEPP), as well as the association with the initial content of polyphenols of the material is scarce. Thus, this work aimed to evaluate the DIC effect, modifying the pressure (0.2 and 0.4 MPa), the number of cycles (2 and 4), and grape pomace material (Malbec, Merlot, and Syrah) on extractable polyphenol (EPP) and NEPP contents. The EPP content increased during DIC application, an effect associated with the pressure, cycles, and initial polyphenol content. While for extractable and non-extractable proanthocyanidin contents, the main factors explaining the DIC effect are the pressure and number of cycles. Therefore, changes in polyphenols from grape pomace by DIC treatment are dependent upon experimental conditions, but the origin of the grape pomace also influences the extraction of EPP.

Modification on the polyphenols and dietary fiber content of grape pomace by instant controlled pressure drop.

Instant controlled pressure drop (DIC) has been used as a pre-treatment to increase extractable polyphenols (EPP), mainly attributed to matrix structure expansion. This work aimed to evaluate the effect of DIC on non-extractable polyphenols (NEPP), EPP, and dietary fiber on grape pomace. At 0.2 MPa-60 s was observe an increase of total EPP and total anthocyanins. Despite the increment of EPP, was observe the lowest anthocyanins and non-extractable proanthocyanidins content at 0.4 MPa-120 s. This increase was due to a partial transformation of anthocyanins into phenolic acids and the depolymerization of proanthocyanidins. Also was observe partial solubilization of insoluble dietary fiber. Morphologically, the size of the pores generated by DIC was more significant at higher pressures. Thus, DIC modified the morphology and profile of the polyphenols of grape pomace, producing phenolic compounds of simpler structure and improving their antioxidant capacities.

Acute supplementation with grapes in obese subjects did not affect postprandial metabolism: a randomized, double-blind, crossover clinical trial.

PURPOSE: The aim of this study was to determine whether grape polyphenols have a "second-meal effect", modulating glucose and lipid elevations in the postprandial period after two successive meals in subjects with obesity. METHODS: A randomized, double-blind, placebo-controlled, acute clinical trial was conducted. Twenty-five obese subjects (BMI = ≥ 30 and < 40 kg/m2) were randomly divided into two groups. At an initial visit, blood was collected in a fasting state and the subjects received breakfast and 46 g of either grape powder (equivalent to 252 g fresh grapes) or placebo, both solved in water. Lunch was provided 5 h later and then blood was collected after 0, 30, 60, 120, 180, 240, 300, 330, 360, and 420 min since arrival. Two weeks later, at a second visit, the subjects received the other powder. The following were determined: glucose, insulin, triglycerides, uric acid, blood count, hemoglobin, viscosity, antioxidant capacity, and satiety perception. RESULTS: Postprandial increases were observed as expected in, for example, glucose and triglycerides after breakfast and lunch. The grape powder supplementation did not cause any significant modification compared to placebo, in these parameters; nor did it significantly modify plasma antioxidant capacity in the 6 h postprandial period. DISCUSSION: Single grape powder supplementation did not modify postprandial responses in obese subjects, probably because the polyphenol dose was insufficient to induce such an effect. The result of a combination of grape with other polyphenol-rich products or chronic supplementation with grape powder on postprandial responses remains to be elucidated. TRIAL REGISTRATION NUMBER: www.clinicaltrials.gov , NCT03741218.

Inter-Individual Variability in Insulin Response after Grape Pomace Supplementation in Subjects at High Cardiometabolic Risk: Role of Microbiota and miRNA.

SCOPE: Dietary polyphenols have shown promising effects in mechanistic and preclinical studies on the regulation of cardiometabolic alterations. Nevertheless, clinical trials have provided contradictory results, with high inter-individual variability. This study explores the role of gut microbiota and microRNAs (miRNAs) as factors contributing to the inter-individual variability in polyphenol response. METHODS AND RESULTS: 49 subjects with at least two factors of metabolic syndrome are divided between responders (n = 23) or non-responders (n = 26), depending on the variation rate in fasting insulin after grape pomace supplementation (6 weeks). The populations of selected fecal bacteria are estimated from fecal deoxyribonucleic acid (DNA) by quantitative real-time polymerase chain reaction (qPCR), while the microbial-derived short-chain fatty acids (SCFAs) are measured in fecal samples by gas chromatography. MicroRNAs are analyzed on a representative sample, followed by targeted miRNA analysis. Responder subjects show significantly lower (p < 0.05) Prevotella and Firmicutes levels, and increased (p < 0.05) miR-222 levels. CONCLUSION: After evaluating the selected substrates for Prevotella and target genes of miR-222, these variations suggest that responders are those subjects exhibiting impaired glycaemic control. This study shows that fecal microbiota and miRNA expression may be related to inter-individual variability in clinical trials with polyphenols.

Exploring the potential of common iceplant, seaside arrowgrass and sea fennel as edible halophytic plants.

The recent interest in diversification in food consumption and the current salinization and desertification processes of farmland have placed the focus on halophytic plants as new food, making necessary the characterization of their biochemical composition and the identification of possible bioactive compounds. In this work, three edible halophytic plants were characterized: common iceplant (Mesembryanthemum crystallinum), sea fennel (Crithmum maritimum), and seaside arrowgrass (Triglochin maritima). The plants studied were a good source of minerals. Sea fennel showed high contents of dietary fibre and calcium (8.5 ppm, wet weight), common iceplant had a high potassium content (6500 ppm, wet weight), while seaside arrowgrass presented high levels of iron (62 ppm, wet weight). The glucose content of the three species was below 30 mg/g per dried weight. The Sb, Pb, Cr, As, Cd, and Hg content was negligible. Polyunsaturated fatty acids, mainly α-linolenic and linoleic acid, prevailed in the three species analyzed. Hydroxycinnamic and hydroxybenzoic acids predominated in common iceplant and sea fennel. Glycosylated flavones, especially isoorientin, prevailed in seaside arrowgrass. These plants present a relevant nutritional profile for which their use as foods or ingredients should be promoted.

Effects of acute intake of grape/pomegranate pomace dietary supplement on glucose metabolism and oxidative stress in adults with abdominal obesity.

A controlled acute, cross-over clinical study (NCT02710461) was performed in order to evaluate the effects on glucose metabolism of a grape/pomegranate pomace dietary supplement in subjects with abdominal obesity (aged 40-60, n = 20). A standard 75 g oral glucose tolerance test (OGTT) was administered alone, together with or 10 h after the consumption of 10 g of the dietary supplement, rich in both extractable (0.4 g) and non-extractable (1.4 g) polyphenols. The dietary supplement did not ameliorate glucose or insulin at any sampling time. No improvement in antioxidant capacity was observed in plasma or urine, concordant with no increased urine polyphenol excretion. A tendency towards improved insulin sensitivity was observed when the product was consumed 10 h before glucose solution. These results suggest that a single realistic dose of grape/pomegranate pomace is not able to clearly improve glucose metabolism; chronic intake remains to be evaluated.

Comparison of the bioactive potential of Roselle (Hibiscus sabdariffa L.) calyx and its by-product: Phenolic characterization by UPLC-QTOF MSE and their anti-obesity effect in vivo.

The aim of the present study was to evaluate extractable (EPP), non-extractable polyphenols (NEPP) and organic acid in Roselle by-product, as well as its potential health beneficial effects in obesity control and their complication in rats fed with high caloric diet. Roselle by-product showed a higher content of dietary fiber and NEPP than Roselle calix, which was was a better source of EPP (P < .05). The UPLC-QTOF MSE analysis allowed the tentative identification of 34 EPP, and 3 hydrolysable polyphenols (NEPP), and 2 organic acids in calyx and by-product. Rats fed with a high caloric diet supplemented with 4% of dietary fiber from by-products and Roselle calyx powder generated a reduction in body weight gain (10% and 14%), adipocytes hypertrophy (17% and 13%) and insulin resistance (48% and 59%) and hepatic steatosis (15% and 25%; respectively) compared with rats fed with a high caloric diet alone. Interestingly, even though Roselle by-product has low EPP contents showed comparable beneficial health effects than Roselle calyces. These effects could be associated with high content of dietary fiber and NEPP. Together, the results of the present study indicate that Roselle by-products could be a potential ingredient to develop functional foods against obesity and its complications.

Phenolic Metabolites in Plasma and Thigh Meat of Chickens Supplemented with Grape Byproducts.

Grape byproducts are rich sources of polyphenols with powerful antioxidant and health-promoting effects. The impact of supplementing chicken diets with grape byproducts on plasma and thigh meat concentrations of phenolic metabolites was evaluated by analyzing samples by high-performance liquid chromatography quadrupole time of flight mass spectrometry. Chickens were fed three experimental diets: Control diet, Control+8% grape pomace, and Control+0.1% grape seed extract. In plasma, 32 phenolic metabolites were identified, some of which were conjugated catechin/epicatechin metabolites exclusively identified in chickens fed diets enriched in grape byproducts. Also, these chickens showed significantly higher plasmatic concentrations of 21 phenolic metabolites. In thigh meat, 14 phenolic metabolites were identified, but no differences were found between diets. Higher plasmatic tocopherol was found when supplementing diets with grape byproducts, while no changes were observed in meat. Thus, supplementing chicken diets with grape byproducts leads to a significant increase in the circulation of phenolic metabolites and tocopherol.

A 6-week supplementation with grape pomace to subjects at cardiometabolic risk ameliorates insulin sensitivity, without affecting other metabolic syndrome markers.

Grape polyphenols have shown a promising role in the modulation of metabolic syndrome (MetS), mostly in animal models. However, clinical studies are scarce and they usually only consider a fraction of polyphenols, ignoring the non-extractable polyphenols (high molecular weight compounds or associated with macromolecules such as dietary fibre). This study aimed at evaluating the effect of grape pomace, rich in both extractable and non-extractable polyphenols, on markers of MetS. Fifty subjects (22 women) aged 20-65 with at least two MetS factors were randomly assigned to the product (daily dose of 8 g of dried grape pomace) or to the control group in a 6 week crossover design with a 4 week wash-out. Samples were collected at the beginning and at the end of both periods; half of the participants were subjected to an oral glucose tolerance test at the beginning and the end of the supplementation period. Grape pomace supplementation significantly improved fasting insulinaemia (p < 0.01), without affecting other cardiometabolic risk parameters. A tendency towards an improvement in postprandial insulinaemia was observed, particularly in those subjects with higher fasting insulin levels. Therefore, supplementation with grape pomace may be a strategy for improving insulin sensitivity in subjects at high cardiometabolic risk.

Fruit peels as sources of non-extractable polyphenols or macromolecular antioxidants: Analysis and nutritional implications.

Despite increasing interest in the relevance of non-extractable polyphenols (NEPP) or macromolecular antioxidants as food bioactive compounds, most studies on their presence in foods focus mainly on the edible part of specific fruits, but their potential presence in fruit peels is usually ignored. The aim of this study was to evaluate NEPP content in the peels from ten common fruits. The results showed that NEPP made up more than half of the total polyphenol contents in half of the studied samples. HPLC analysis showed that NEPP were constituted by phenolic acids, flavanols and flavonols. Also, it was found that peels accounted for >40% of total NEPP in the fruit in four of the samples analysed. These results should encourage both the use of fruit peels in the fruit industry as ingredients and the consumption of whole fruits given the significant presence of NEPP in fruit peels.

A high-fat high-sucrose diet affects the long-term metabolic fate of grape proanthocyanidins in rats.

PURPOSE: Polyphenol metabolites are key mediators of the biological activities of polyphenols. This study aimed to evaluate the long-term effects of a high-fat high-sucrose (HFHS) diet on the metabolism of proanthocyanidins from grape seed extract (GSE). METHODS: Adult female Wistar-Kyoto rats were fed a standard (STD) or HFHS diet supplemented or not with GSE for 16 weeks. PA metabolites were determined by targeted HPLC-MS/MS analysis. RESULTS: A lower concentration of total microbial-derived PA metabolites was present in urine and the aqueous fraction of faeces in the HFHS + GSE group than in the STD + GSE group. In contrast, a tendency towards the formation of conjugated (epi)catechin metabolites in the HFHS + GSE group was observed. CONCLUSIONS: These results show that a HFHS diet significantly modifies PA metabolism, probably via: (1) a shift in microbial communities not counteracted by the polyphenols themselves; and (2) an up-regulation of hepatic enzymes.

Comprehensive Characterization of Extractable and Nonextractable Phenolic Compounds by High-Performance Liquid Chromatography-Electrospray Ionization-Quadrupole Time-of-Flight of a Grape/Pomegranate Pomace Dietary Supplement.

Grape and pomegranate are rich sources of phenolic compounds, and their derived products could be used as ingredients for the development of functional foods and dietary supplements. However, the profile of nonextractable or macromolecular phenolic compounds in these samples has not been evaluated. Here, we show a comprehensive characterization of extractable and nonextractable phenolic compounds of a grape/pomegranate pomace dietary supplement using high-performance liquid chromatography-electrospray ionization-quadrupole time-of-flight (HPLC-ESI-QTOF) and matrix-assisted laser desorption/ionization (MALDI)-TOF techniques. The main extractable phenolic compounds were several anthocyanins (principally malvidin 3-O-glucoside) as well as gallotannins and gallagyl derivatives; some phenolic compounds were reported in grape or pomegranate for the first time. Additionally, there was a high proportion of nonextractable phenolic compounds, including vanillic acid, and dihydroxybenzoic acid. Unidentified polymeric structures were detected by MALDI-TOF MS analysis. This study shows that mixed grape and pomegranate pomaces are a source of different classes of phenolic compounds including a high proportion of nonextractable phenolic compounds.

Influence of omega-3 PUFAs on the metabolism of proanthocyanidins in rats.

Studies of the bioavailability of proanthocyanidins usually consider them independently of other dietary constituents, while there is a tendency in the field of functional foods towards the combination of different bioactive compounds in a single product. This study examined the long-term effects of ω-3 polyunsaturated fatty acids of marine origin on the metabolic fate of grape proanthocyanidins. For this, female adult Wistar-Kyoto rats were fed (18weeks) with a standard diet supplemented or not with eicosapentaenoic acid/docosahexaenoic acid (1:1, 16.6g/kg feed), proanthocyanidin-rich grape seed extract (0.8g/kg feed) or both. A total of 39 microbial-derived metabolites and 16 conjugated metabolites were detected by HPLC-MS/MS either in urine or in the aqueous fraction of feces. An unexpected significant increase in many proanthocyanidin metabolites in urine and feces was observed in the group supplemented with ω-3 polyunsaturated fatty acids group as compared to the animals fed a standard diet, which contains a small amount of polyphenols. However, proanthocyanidin metabolites in rats given ω-3 polyunsaturated fatty acids and grape seed extract did not significantly differ from those in the group supplemented only with grape seed extract. It was concluded that ω-3 polyunsaturated fatty acids collaborate in the metabolism of polyphenols when present at low doses in the feed matrix, while the capacity of ω-3 polyunsaturated fatty acids to induce microbiota transformations when proanthocyanidins are present at high doses is not relevant compared to that of polyphenols themselves.

The combined action of omega-3 polyunsaturated fatty acids and grape proanthocyanidins on a rat model of diet-induced metabolic alterations.

It has been suggested that food components such as ω-3 polyunsaturated fatty acids (ω-3 PUFAs) and (poly)phenols counteract diet-induced metabolic alterations by common or complementary mechanisms. To examine the effects of a combination of ω-3 PUFAs and (poly)phenols on such alterations, adult Wistar-Kyoto rats were fed an obesogenic high-fat high-sucrose diet supplemented, or not, for 24 weeks with: eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) 1 : 1 (16.6 g kg(-1) feed); proanthocyanidin-rich grape seed extract (GSE, 0.8 g kg(-1) feed); or EPA/DHA 1 : 1 + GSE. Body weight, feed intake, and plasma glucose were evaluated every 6 weeks, while adipose tissue weight, insulin, glucagon, ghrelin, leptin, adiponectin, cholesterol, and triglycerides were evaluated at the end of the experiment. ω-3 PUFAs reduced plasma leptin and cholesterol levels, but did not modify diet-induced perigonadal fat or plasma insulin levels; while GSE increased plasma triglyceride levels. The combined action of ω-3 PUFAs and the proanthocyanidins reduced plasma insulin and leptin, as well as partially prevented perigonadal fat accumulation. While separate supplementation with ω-3 PUFAs or grape proanthocyanidins may not counteract all the key metabolic changes induced by a high-energy-dense diet, the combination of both supplements reverts altered insulin, leptin and triglyceride levels to normal.

Effect of n-3 PUFA supplementation at different EPA:DHA ratios on the spontaneously hypertensive obese rat model of the metabolic syndrome.

The increasing incidence of the metabolic syndrome (MetS), a combination of risk factors before the onset of CVD and type 2 diabetes, encourages studies on the role of functional food components such as long-chain n-3 PUFA as preventive agents. In the present study, we explore the effect of EPA and DHA supplementation in different proportions on spontaneously hypertensive obese (SHROB) rats, a model for the MetS in a prediabetic state with mild oxidative stress. SHROB rats were randomised into four groups (n 7), each supplemented with EPA/DHA at ratios of 1:1, 2:1 and 1:2, or soyabean oil as the control for 13 weeks. The results showed that in all the proportions tested, EPA/DHA supplementation significantly lowered total and LDL-cholesterol concentrations, compared with those of the control group. EPA/DHA supplementation at the ratios of 1:1 and 2:1 significantly decreased inflammation (C-reactive protein levels) and lowered oxidative stress (decreased excretion of urinary isoprostanes), mainly at the ratio of 1:2. The activity of antioxidant enzymes increased in erythrocytes, abdominal fat and kidneys, with magnitudes depending on the EPA:DHA ratio. PUFA mixtures from fish affected different MetS markers of CVD risk factors in SHROB rats, depending on the ratios of EPA/DHA supplementation. The activation of endogenous defence systems may be related to the reduction of inflammation and oxidative stress.

Targets of protein carbonylation in spontaneously hypertensive obese Koletsky rats and healthy Wistar counterparts: a potential role on metabolic disorders.

The study innovatively pinpoints target proteins of carbonylation, a key PTM induced by oxidative stress, in the SHROB (genetically obese spontaneously hypertensive) rat model of metabolic syndrome (MetS). Protein carbonylation was assessed by a fluorescence-labeling proteomics approach, and complemented with biometric and biochemical markers of MetS. SHROB and healthy Wistar rats were fed two diets, soybean and linseed oil supplementations, in order to distinguish intrinsic carbonylation of SHROB animals from diet-modulated carbonylation unrelated to MetS. First exploratory data showed similar carbonylation patterns and metabolic conditions in SHROB rats fed soybean and linseed, but different from Wistar animals. A total of 18 carbonylated spots in liver, and 12 in skeletal tissue, related to pathways of lipid (29.6%), carbohydrate (25.9%) and amino acid (18.5%) metabolisms, were identified. In particular, SHROB animals present higher carbonylation in four liver proteins belonging to lipid metabolism, redox regulation and chaperone activity (ALDH2, PDI, PDIA3, PECR), and in the skeletal muscle ALDOA that is involved in muscle dysfunction. Conversely, SHROB rats display lower carbonylation in liver albumin, AKR1C9, ADH1 and catalase. This investigation provides a novel perspective of carbonylation in the context of metabolic disorders, and may be a starting point to characterize new redox pathways exacerbating MetS. BIOLOGICAL SIGNIFICANCE: Oxidative stress is a concomitant factor in the pathogenesis of MetS that induces oxidative PTM as carbonylation. Through the use of a redox proteomics approach, we have thoroughly mapped the occurrence of protein targets of carbonylation in the genetically-induced MetS model SHROB rat. The present research brings a new insight of MetS pathogenesis and it may provide valuable information to understand the biological impact of oxidative stress in patients with MetS.

Protective effect of the omega-3 polyunsaturated fatty acids: Eicosapentaenoic acid/Docosahexaenoic acid 1:1 ratio on cardiovascular disease risk markers in rats.

BACKGROUND: High consumption of fish carries a lower risk of cardiovascular disease as a consequence of dietary omega-3 long chain polyunsaturated fatty acid (n-3 PUFA; especially EPA and DHA) content. A controversy exists about the component/s responsible of these beneficial effects and, in consequence, which is the best proportion between both fatty acids. We sought to determine, in healthy Wistar rats, the proportions of EPA and DHA that would induce beneficial effects on biomarkers of oxidative stress, and cardiovascular disease risk. METHODS: Female Wistar rats were fed for 13 weeks with 5 different dietary supplements of oils; 3 derived from fish (EPA/DHA ratios of 1:1, 2:1, 1:2) plus soybean and linseed as controls. The activities of major antioxidant enzymes (SOD, CAT, GPX, and GR) were determined in erythrocytes and liver, and the ORAC test was used to determine the antioxidant capacity in plasma. Also measured were: C reactive protein (CRP), endothelial dysfunction (sVCAM and sICAM), prothrombotic activity (PAI-1), lipid profile (triglycerides, cholesterol, HDLc, LDLc, Apo-A1, and Apo-B100), glycated haemoglobin and lipid peroxidation (LDL-ox and MDA values). RESULTS: After three months of nutritional intervention, we observed statistically significant differences in the ApoB100/ApoA1 ratio, glycated haemoglobin, VCAM-1, SOD and GPx in erythrocytes, ORAC values and LDL-ox. Supplementation with fish oil derived omega-3 PUFA increased VCAM-1, LDL-ox and plasma antioxidant capacity (ORAC). Conversely, the ApoB100/ApoA1 ratio and percentage glycated haemoglobin decreased. CONCLUSIONS: Our results showed that a diet of a 1:1 ratio of EPA/DHA improved many of the oxidative stress parameters (SOD and GPx in erythrocytes), plasma antioxidant capacity (ORAC) and cardiovascular risk factors (glycated haemoglobin) relative to the other diets.

Effect of pressurized hot water extraction on antioxidants from grape pomace before and after enological fermentation.

Grape pomace was extracted with pressurized hot water at laboratory scale before and after fermentation to explore the effects of fermentation and extraction temperature (50-200 °C) and time (5 and 30 min) on total extracted antioxidant levels and activity and to determine the content and recovery efficiency of main grape polyphenols, anthocyanins, and tannins. Fermented pomace yielded more total antioxidants (TAs), antioxidant activity, and tannins, than unfermented pomace but fewer anthocyanins. Elevating the extraction temperature increased TA extraction and antioxidant activity. Maximum anthocyanin extraction yields were achieved at 100 °C and at 150 °C for tannins and tannin-anthocyanin adducts. Using higher temperatures and longer extraction times resulted in a sharp decrease of polyphenol extraction yield. Relevant proanthocyanidin amounts were extracted only at 50 and 100 °C. Finally, TA recovery and activity were not directly related to the main polyphenol content when performing pressurized hot water grape pomace extraction.