Non-extractable Proanthocyanidins Research Articles

Acid hydrolysis conditions do affect the non-extractable phenolic compounds composition from grape peel and seed

This study aimed to evaluate the effect of hydrolysis conditions on non-extractable phenolic compounds (NEPC) composition of grape peel and seed powder. The effect of temperature (50–90 °C), hydrochloric acid concentration (0.1–15.0 %), and time (5–20 min) were evaluated to understand their impact on NEPC release/extraction and degradation. The use of 1.0 and 8.0 % of HCl concentrations (v/v) and temperatures of 65 and 80 °C produced extracts with higher concentrations and a larger set of compounds. These conditions promoted a balance between release/extraction and degradation processes, thereby maximizing the NEPC content in the extracts. Furthermore, the results suggest that hydrolysis conditions can be set to modulate the release of specific classes. Non-extractable proanthocyanidins showed higher concentrations when intermediate values of temperature and acid concentration were applied. Hydrolysable tannins and hydroxybenzoic acids, on the other hand, were better extracted using higher acid concentrations and higher temperatures. The results suggest that the concentration and composition of NEPC are influenced by the hydrolysis conditions and the type of matrix. Hence, it is crucial to account for this compositional variation when conducting research on the biological effects of NEPC and when using this fraction as supplements or food ingredients.

In Vivo Evaluation of the Cardiometabolic Potential of Grape Pomace: Effect of Applying Instant Controlled Pressure Drop.

Grape pomace (GP) is a source of polyphenols which may be present as free structures or associated with dietary fiber. Instant controlled pressure drop (DIC) is a technology which can modify the association of polyphenols with food matrixes, but how these modifications affect the health benefits associated with GP remains to be elucidated. In this study, in rats fed a high-fat-fructose diet (HFF), we evaluated the in vivo cardiometabolic effects of the modification of polyphenols in GP caused by DIC at 0.2 MPa for 60 s (DIC1) and 0.4 MPa for 120 s (DIC2). These treatments increased anthocyanin and total flavonoid contents, respectively, while all the supplementations caused significant improvements in insulin resistance and plasma triacylglycerols. Thus, the bioactive compounds present in GP (including a major fraction of non-extractable proanthocyanidins) caused these modifications independently of the specific polyphenol profiles which may have resulted from these DIC treatments. Additionally, only intact GP led to an increase in HDL cholesterol, while only DIC2-treated GP improved hepatic steatosis. In conclusion, GP always improves insulin sensitivity in this animal model of obesity, while the different compositions of GP modified by DIC may be associated with other cardiometabolic parameters.

Exploring a cocoa–carob blend as a functional food with decreased bitterness: Characterization and sensory analysis

Cumulative evidence indicates the relevance of cocoa in the modulation of cardiometabolic diseases. Nevertheless, pure cocoa may be rejected by many consumers due to its bitter taste. Carob (Ceratonia siliqua L.) is a Mediterranean legume with pods rich in dietary fibre and polyphenols. In this study, carob flour was combined with cocoa, to obtain a blend which was subjected to nutritional evaluation (proximate composition, carbohydrate and fatty acid profiles, phytochemical composition, dietary fibre properties, antioxidant capacity) and sensory analysis, in order to determine whether it may be a suitable alternative to commercial sugar-rich soluble cocoa powders. The blend showed a high content of dietary fibre (56%), methylxanthines and polyphenols (55% as non-extractable proanthocyanidins). The product had good solubility and was less bitter than cocoa, as evaluated in sensory analysis, thereby suggesting that this blend may be acceptable to consumers, particularly when information about potential biological activity is provided (a significant improvement in taste evaluation was observed). The beneficial environmental impact of carob and the advantages of valorizing the commonly discarded carob pod mean that further studies of applications of this blend and its potential health effects would be of great interest.

Chia seeds and chemical‐elicited sprouts supplementation ameliorates insulin resistance, dyslipidemia, and hepatic steatosis in obese rats

Chia seeds (CS) and sprouts are rich in bioactive compounds. This study aimed to assess the effects of germination and chemical elicitation (salicylic acid [SA]; hydrogen peroxide [H2 O2 ]) on proximate chemical, total phenolics compounds (TPC), non-extractable proanthocyanidins (NEPA), and carotenoids content of chia sprouts; besides, the effects of their supplementation on obesity-associated complications in rats fed with high-fat and fructose diet (HFFD) were evaluated. Protein, carbohydrate, TPC, NEPA, and carotenoids content were higher in sprouts than CS; elicitation enhanced TPC and carotenoids compared to non-elicited (NE) sprouts. CS, NE, and elicited chia sprouts ameliorated insulin resistance and dyslipidemia at the same level in HFFD-fed rats. NE and SA-chia sprouts exerted the biggest reduction in hepatic triglycerides, which could be partially related to inhibition of pancreatic lipase activity. In addition, SA elicitation induced the greatest effect on insulin levels and corporal weight. CS and their sprouts decreased obesity and its complication, mainly SA-elicited sprouts. PRACTICAL APPLICATIONS: The growing epidemic of non-communicable diseases such as diabetes and obesity has led to the search for prevention and treatment through lifestyle changes, including the consumption of foods rich in bioactive compounds, such as seeds and their sprouts. Since sprouts contain higher concentrations of bioactive compounds and nutrients than seed, germination is a natural alternative to produce ready-to-eat functional foods. Chemical elicitation is a strategy to increase even more the bioactivity of sprouts. CS has been recognized for its beneficial health effects ameliorating dyslipidemia and insulin resistance. This study demonstrates that elicitation, with SA and H2 O2 , during germination of CS, increases the nutrient and phytochemical content of sprouts, with beneficial effects on body weight gain, insulin resistance, dyslipidemia, and prevention of NAFLD progression in diet-induced obese rats. Therefore, chia sprouts, natural and elicited, may be used as potential nutraceutical foods for the prevention and treatment of obesity and its complications.

In vitro and in vivo evaluation of the bile acid-binding properties of dried persimmon and its non-extractable proanthocyanidin fraction

Dried persimmons contain abundant insoluble tannins comprised of non-extractable proanthocyanidins (NEPAs). To determine the beneficial function of NEPAs, we studied the bile acid-binding ability of NEPAs using in vitro and in vivo experiments. For the in vitro evaluation, 70% (v/v) acetone-insoluble solids (AIS) with different NEPA levels was prepared from persimmon fruits during drying. AIS with higher NEPA levels displayed stronger bile acid-binding activity, and the highest NEPA levels can be obtained from mostly-dried fruits. The in vivo bile acid-excreting effect of dried persimmon powder (DP) and AIS was verified by feeding experiments using C57BL/6J mice. The average bile acid-excretion was in order of low-fat group (1.07 µmol/day) < high-fat (HF) group (3.03 µmol/day) < HF + AIS group (4.44 µmol/day) < HF + DP group (6.74 µmol/day). These results suggest that the bile acid-excreting function of the fruit is related to the presence of NEPAs, which are constitutive ingredients of dried persimmon.

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.

The Effect of Emulsifying Protein and Addition of Condensed Tannins on n-3 PUFA Enriched Emulsions for Functional Foods.

This paper examines the effect of the type of the emulsifying protein (EP) (sodium caseinate (SC) and whey protein isolate (WPI)) on both oil-in-water liquid-like emulsions (Es) and the corresponding cold gelled emulsions (GEs), and also the effect of addition of carob extract rich in condensed tannins (T). The systems, intended as functional food ingredients, were studied in various different respects, including rheological behaviour, in vitro gastrointestinal digestion with determination of the release of non-extractable proanthocyanidins (NEPA) from T, antioxidant activity and lipolysis. EP significantly affects the rheological behaviour of both Es and GEs. T incorporation produced a structural reinforcement of GEs, especially in the case of SC. The digests from Es displayed a higher antioxidant activity than those from GEs. T lipase inhibition was observed only in the formulations with WPI. Our results highlight the importance, in the design of functional foods, of analyzing different variables when incorporating a bioactive compound into a food or emulsion in order to select the better combination for the desired objective, owing to the complex interplay of the various components.

Characterization of jabuticaba (Plinia cauliflora) peel flours and prediction of compounds by FTIR analysis

Jabuticaba peels present high levels of bioactive compounds. The production of flours from these peels can be a strategy for their conservation. Thus, the objectives of this study were to produce flours from jabuticaba peels, to examine the feasibility of employing Fourier Transform Infrared (FTIR) measurements for their chemical characterization and to verify the existence of correlations among measured parameters. Flours composition showed high variability in insoluble dietary fiber (IDF) contents (26.99–46.33 g/100 g), soluble dietary fiber (SDF) contents (4.41–9.27 g/100 g), total extractable phenolics (TEP) (8.90–16.49 g GAE/100 g), non-extractable proanthocyanidins (NEPA) (842.88–1889.06 mg/100 g), anthocyanins (TMA) (344.00–1304.52 mg/100 g) and carotenoids (1925.22–4296.41 μg/100 g). Moderate correlations were noted between SDF and TEP and NEPA, and between IDF and anthocyanins. Partial least squares (PLS) chemometric models, based on the FITR data, were able to provide satisfactory predictions of TEP, TMA, SDF and IDF contents, similar to conventional analytical methods.

Non-extractable polyphenols and in vitro bile acid-binding capacity of dried persimmon (Diospyros kaki) fruit

Dried persimmon is thought to be a rich source of non-extractable polyphenols (NEPPs). Here, we analyzed the NEPP content of dried persimmon and its bile acid-binding activity in vitro. To determine total NEPP content and epicatechin equivalent (ECE) of intact NEPPs, acid hydrolysis and non-destructive methods with 70% (v/v) acetone-insoluble solids (AIS), respectively, were conducted using Folin-Ciocalteu reagent. The ECE of intact NEPPs exceeded 1000 mg/100 g in the non-destructive method, but total NEPP content was approximately 3900 mg/100 g with the acid hydrolysis method. Thiolysis showed that the non-extractable proanthocyanidins in dried persimmon mainly comprised epigallocatechin-gallate, epigallocatechin, epicatechin, and epicatechin-gallate. AIS from dried persimmon showed stronger bile acid-binding activity than AIS from apple, quince, and fresh astringent persimmon. These results suggest that the high content of NEPPs in dried persimmon may contribute to a strong bile acid-binding activity.

Emulsion gels containing n-3 fatty acids and condensed tannins designed as functional fat replacers

The purpose of this study was to ascertain the potential of several food-grade emulsion (O/W) gels (GEs) for use as healthier fat replacers. The emulsions, formulated with a lipid phase rich in n-3 fatty acids and different emulsifiers (sodium caseinate, SC; whey protein isolate, WPI and isolated soy protein, ISP), were cold gelled after adding a natural extract rich in condensed tannins (CT). The GEs were characterized and their oxidative stability evaluated during storage (4 °C). All GEs formulated presented a solid-like structure showing generally excellent emulsion stability, which improved in GEs with the addition of CT. Non-extractable proanthocyanidins (NEPA) were the main source of polyphenol in samples enriched with CTs. The antioxidant activity of the systems was not affected by the use of different proteins as emulsifiers, but it was improved in GEs containing CT. The oxidation values recorded in the GE systems can generally be regarded as low even considering their enrichment with unsaturated fatty acids, which thus assures their suitability for use as fat replacers.

Buriti (Mauritia flexuosa L. f.) fruit by-products flours: Evaluation as source of dietary fibers and natural antioxidants

Buriti by-products flours were evaluated as sources of dietary fibers and natural antioxidants. All flours presented chemical characteristics that allowed classification as high dietary fiber powders. Presence of pectic polysaccharides, arabinoxylans and xyloglucans was inferred by the neutral monosaccharides profile. Peels and defatted pulp flours are highlighted as those with higher antioxidant potential (total extractable polyphenols and antioxidant activities by DPPH and FRAP) compared to endocarp and manually-produced bran flours. Carotenoids content were also higher in the peels flours. All produced flours showed expressive amounts of total non-extractable proanthocyanidins (NEPA). Buriti peels flours NEPA levels are among the highest values previously described in the literature. Blanching preserved the extractable polyphenols but not carotenoids or NEPA. Technological properties were influenced mainly by the size of the particles. Buriti by-products flours have potential to be used as sources of dietary fiber and natural antioxidants in food.

Physicochemical characterization, antioxidant capacity, total phenolic and proanthocyanidin content of flours prepared from pequi (Caryocar brasilense Camb.) fruit by-products

The potential of pequi by-products as substrates for the production of flours rich in antioxidant dietary fibers was evaluated. Dietary fiber contents ranged from 39.8 to 43.3g/100g with pectic polysaccharide fraction constituted of rhamnogalacturonans and hemicellulose fraction consisted of arabinogalactans, xylans and glucomannans. Total polyphenols, non-extractable proanthocyanidins (NEPA) and carotenoid contents of the flours were determined (respectively, 15.5-17.4g GAE/100g, 215.54-346.84mg/100g and 2116.52-3499.03μg/100g). The antioxidant capacities of pequi by-product flours (986.94-1154.42μM TE/g ABTS; 44.43-48.02g/g DPPH; and 3027.31-3216.27μmol Fe2SO4/g FRAP) were found to be exceptionally higher than those of fruits and fruits by-products reported in the literature. Exocarp removal promoted no significant changes in the technological properties of the flour, except for color. Results showed promising prospects for future exploitation of pequi peel as a potential source of dietary fiber and natural antioxidants.

Concentrations of oligomers and polymers of proanthocyanidins in red and purple rice bran and their relationships to total phenolics, flavonoids, antioxidant capacity and whole grain color

Proanthocyanidins, a flavonoids subgroup, are proposed to have chronic disease modulation properties. With the eventual goal of enhancing rice phytonutrient concentrations, we investigated the genotypic variation of the concentrations of individual oligomers and polymers of proanthocyanidins in red and purple rice brans. A 4.3-fold variation in total proanthocyanidins (sum of oligomers and polymers) in the extractable fraction was found and the concentration was highly correlated with total phenolics, total flavonoids and antiradical capacity. Variation in the proportion of oligomers and polymers existed, with monomers to trimers, 4–6mers, 7–10mers and polymers accounting for 7, 18, 26.5 and 48.7%, respectively, of the total. The redness value a∗ of whole grain rice measured in CIE L∗a∗b∗ color space was negatively and positively correlated with extractable and non-extractable proanthocyanidins, respectively. The variation found indicates it is possible to select rice with bran containing high levels of total proanthocyanidins and specific degree of polymerization profiles.

Assessing non-digestible compounds in apple cultivars and their potential as modulators of obese faecal microbiota in vitro

The health benefits of apple bioactive compounds have been extensively reported. However, only few studies have focused on bioactive compounds that are not absorbed and metabolised during gastrointestinal digestion and can induce changes in microbial populations of faeces. We have characterised Braeburn, Fuji, Gala, Golden Delicious, Granny Smith, McIntosh and Red Delicious cultivars and found significant differences for extractable phenolics (1.08–9.2mg/g) non-extractable proanthocyanidins (3.28–5.7mg/g), and dietary fibre (20.6–32.2%) among cultivars with Granny Smith having the highest contents. Granny Smith was used after in vitro digestion for fermentation of faeces from diet-induced obese mice. Results showed that relative abundances of Firmicutes, Bacteroidetes, Enterococcus, Enterobacteriaceae, Escherichia coli, and Bifidobacterium in apple cultured faeces tended to resemble the abundance in faeces from lean mice with increased trend in the production of butyric acid. These results suggest that apple non-digestible compounds might help to re-establish a disturbed microbiota balance in obesity.

Contents of extractable and non-extractable polyphenols in the leaves of blueberry

The contents of extractable polyphenols (EPP), non-extractable polyphenols (NEPP), extractable proanthocyanidins (EPAC), non-extractable proanthocyanidins (NEPAC) and extractable anthocyanidins (EAC) in blueberry leaves were investigated. An experiment was conducted to analyse the effect of solvent types (methanol and ethanol), concentration (50 and 70%) and pH (2 and 6) on the extraction of bioactive compounds. Total extractable polyphenols (TEPP), total extractable proanthocyanidins (TEPAC), and total extractable anthocyanidins (TEAC) were analysed in methanol/ethanol/water extracts, NEPP were determined in acidic hydrolysates and NEPAC were quantified by depolymerisation in HCl/butanol. The results showed that ethanol and methanol did not affect the extraction of TEPP, while methanol was better for TEPAC and TEAC. The contents of TEPP and TEAC in 50% solvent were higher than those in 70% solvent. When solvent pH dropped to 2, the contents of EPP and EPAC were increased, while the EAC content was decreased. &amp;nbsp;

Improved procedure to determine non-extractable polymeric proanthocyanidins in plant foods

Proanthocyanidins (PA) or condensed tannins, a major group of oligomeric and polymeric dietary polyphenols, have an essential role on the organoleptic and health-related properties of plant foods. Their content is usually determined by HPLC analysis of aqueous–organic extracts. However, appreciable amounts of polymeric PA that remain in the residues of extraction usually are not considered for the analysis. A complete quantification of PA requires an additional determination of these non-extractable PA (NEPA). The objective of this work was to develop a new procedure to determine the content of NEPA, based in depolymerization by butanolysis, which yields anthocyanidin monomers and xanthylium compounds. Samples and standard are treated with butanol/HCl with FeCl3 (100°C, 60 min), and absorbances at 555 nm (anthocyanidins) and 450 nm (xanthylium compounds) are measured in the hydrolysates. NEPA content determined in some plant foods suggests that procedures based just on anthocyanidin concentration overestimate the actual content.

Non-extractable proanthocyanidins from grapes are a source of bioavailable (epi)catechin and derived metabolites in rats

The non-extractable fraction of many fruit and vegetables contains putatively bioactive polyphenolic compounds that, in most cases, have not been well characterised structurally. Non-extractable proanthocyanidins (NEPA) of a polymeric nature are part of the dietary fibre fraction of food. Using liquid chromatography coupled to a mass spectrometer equipped with an electrospray ionisation chamber and a triple quadrupole mass analyser for tandem analysis (HPLC-ESI-QqQ-MS/MS) techniques, we examine the phenolic metabolites present in urine and faeces from rats 24h after ingestion of an NEPA-rich fraction. We show that NEPA are partially depolymerised during their transit along the intestinal tract, as evidenced by the presence of (epi)catechin (EC) monomers and dimers in faeces and phase II conjugates of EC in urine. Moreover, NEPA are further metabolised by the intestinal microbiota into smaller metabolites including phenolic acids that are present in urine as both free phenolics and conjugates with glucuronate or sulphate moieties. For the first time, we report evidence that NEPA behave in vivo as a source of phenolics that are released progressively and deliver phenolic species that come into contact with the intestinal walls and are bioavailable for at least 24h after ingestion.

Nonextractable polyphenols, usually ignored, are the major part of dietary polyphenols: A study on the Spanish diet

Dietary polyphenols (PP) can be divided into two groups: extractable polyphenols (EPP) or compounds solubilized by aqueous organic solvents, and nonextractable polyphenols (NEPP) or compounds that remain in their corresponding extraction residues. Most studies on food polyphenols and dietary intakes address exclusively EPP. The objective of this work was to determine the actual amount of PP, including NEPP, in food and in a whole diet. HPLC-MS analyses were performed to identify EPP in methanol-acetone extracts and NEPP in the acidic hydrolyzates of their extraction residues in cereals, fruits, vegetables, nuts, and legumes. NEPP contents, estimated as hydrolyzable PP plus nonextractable proanthocyanidins (PA), ranged from 880 mg/100 g dry weight in fruits to 210 mg/100 g in cereals and were substantially higher than the contents of EPP. NEPP intake (day/person) in the Spanish diet (942 mg) is higher than EPP intake (258 mg) fruits and vegetables (746 mg) are the major contributors to the total PP intake (1201 mg). Non extractable polyphenols are the major part of dietary polyphenols. The knowledge of intakes and physiological properties of NEPP may be useful for a better understanding of the potential health effects of dietary PP.

Extractable antioxidants and non-extractable phenolics in the total antioxidant activity of selected plum cultivars ( Prunus domestica L .): Evolution during on-tree ripening

The purpose of this study was to evaluate the contribution of extractable antioxidants and non-extractable phenolics to the total antioxidant activity (TAA) of plums. Therefore, the antioxidant activity was determined (ABTS assay) in aqueous–organic extracts, as well as in the extraction residues which were a subject of two different acidic treatments to release hydrolysable tannins and non-extractable proanthocyanidins (NEPA). In addition, the changes in TAA during the last week of ripening were investigated. Extractable antioxidants contributed less than 18% to the TAA, considerably higher values of antioxidant activity were associated with hydrolysable tannins and NEPA, suggesting that the antioxidant activity of plums may be underestimated in the literature. The ripening resulted in an increase of TAA up to 38% in excess of the value determined on the first sampling date. TAA showed a similar pattern over the ripening period for all cultivars studied.

Proanthocyanidin metabolites associated with dietary fibre from in vitro colonic fermentation and proanthocyanidin metabolites in human plasma

Proanthocyanidins (PAs) or condensed tannins, a major group of dietary polyphenols, are oligomers and polymers of flavan-3-ol and flavan-3, 4-diols widely distributed in plant foods. Most literature data on PAs' metabolic fate deal with PAs that can be extracted from the food matrix by aqueous-organic solvents ( extractable proanthocyanidins). However, there are no data on colonic fermentation of non-extractable proanthocyanidins (NEPAs), which arrive almost intact to the colon, mostly associated to dietary fibre (DF). The aim of the present work was to examine colonic fermentation of NEPAs associated with DF, using a model of in vitro small intestine digestion and colonic fermentation. Two NEPA-rich materials obtained from carob pod (Ceratonia siliqua L. proanthocyanidin) and red grapes (grape antioxidant dietary fibre) were used as test samples. The colonic fermentation of these two products released hydroxyphenylacetic acid, hydroxyphenylvaleric acid and two isomers of hydroxyphenylpropionic acid, detected by HPLC-ESI-MS/MS. Differences between the two products indicate that DF may enhance the yield of metabolites. In addition, the main NEPA metabolite in human plasma was 3,4-dihydroxyphenyl acetic acid. The presence in human plasma of the same metabolites as were detected after in vitro colonic fermentation of NEPAs suggests that dietary NEPAs would undergo colonic fermentation releasing absorbable metabolites with potential healthy effects.