Non-extractable Polyphenols Research Articles

High-performance thin-layer chromatography and direct analysis in real time-high resolution mass spectrometry of non-extractable polyphenols from tropical fruit peels

Passiflora species, mangosteen, and cherimoya peels are a source of bioactive phenolic compounds. Nevertheless, a significant fraction of polyphenols, called non-extractable polyphenols (NEPs), are retained in the extraction residue after a conventional extraction. Thus, alkaline, acid, and enzymatic-assisted extractions to recover high contents of antioxidant NEPs from the extraction residue of fruit peels, were compared in this work. A high-performance thin-layer chromatography method with UV/Vis detection was developed in order to obtain the phenolic profile for the extracts. The most intense bands were further analyzed by direct analysis in real-time-high-resolution mass spectrometry to tentatively identified NEPs in fruit peel extracts. Total phenolic and proanthocyanidin contents and antioxidant capacity of the extracts were measured to carry out a multivariate statistical analysis. Alkaline hydrolysis was the most efficient treatment to recover NEPs from fruit peels as well as a promising treatment to obtain antioxidant extracts along with EAE. Cherimoya peel extracts were the richest in antioxidant NEPs. This work highlights that many NEPs remain on the extraction residue of fruit peels after conventional extraction and are not usually taken into account.

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.

Berry by-products obtained from a decoction process are a rich source of low- and high-molecular weight extractable and non-extractable polyphenols

In this study, we carried out an exhaustive characterization of the polyphenol profile of strawberry, raspberry, blueberry, and blackberry decoctions; as well as the extractable (EPP) and hydrolysable (HPP) polyphenolic and proanthocyanidin profile of the residues obtained during berries decoctions (decoction by-products) by UPLC-ESI-Q-ToF MS. A greater variety of polyphenols was identified in the EPP fraction of the berry decoction by-products as compared to the decoctions, which were rich in several ellagitannins, flavonols, hydroxybenzoic acids, and anthocyanins. Ellagic acid was identified as the major polyphenol after acid hydrolysis in all berry decoction by-products, followed by hydroxybenzoic acid, which was found bound to the matrix by glycosidic, ether and ester bonds. Regarding proanthocyanidins, procyanidin, prodelphinidin, and propelargonidin dimers were identified in the strawberry, raspberry, and blackberry decoction by-products by MALDI-ToF MS. The results obtained from this study demonstrates that berries decoctions are rich in polyphenols; however, berry decoction by-products were richer in polyphenols with a great variety of extractable and non-extractable polyphenols.

Extraction, isolation, characterization and antimicrobial activities of non-extractable polyphenols from pomegranate peel

Non-extractable polyphenols (NEPPs) in pomegranate peel were released by acid hydrolysis followed by extraction using ethyl acetate (EtOAc). Ten NEPPs were identified in the hydrolysate using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Six compounds were then isolated from the EtOAc extracts whose structures were identified as β-sitosterol-3-O-glycoside (1), β-sitosterol (2), ursolic acid (3), corosolic acid (4), asiatic acid (5) and arjunolic acid (6) using a wide range of spectroscopic analyses. Compounds 4–6 were isolated for the first time from pomegranate peel. Antimicrobial experiments revealed that compound 3 and 5 showed significant antimicrobial activity against a range of pathogens, particularly compound 5 which exhibited selective inhibitive activity towards Staphylococcus aureus with a minimum inhibitory concentration (MIC) of 16 μg/ml. The present study has provided new insights into the composition of bound chemicals in pomegranate peel and laid a foundation for improving its further processing and utilization.

Citrus decoction by-product represents a rich source of carotenoid, phytosterol, extractable and non-extractable polyphenols

This study aimed to carry out an exhaustive chemical characterization of citrus (orange, mandarin, and grapefruit) decoctions as well as the residues obtained during the decoction process (by-products). The citrus decoctions were rich in hesperidin, naringin, and narirutin, but carotenoids and phytosterols were not detected. Interestingly, these flavanones were found in a higher concentration in the extractable polyphenol fraction of the citrus decoction by-products. Moreover, the greatest content of hesperidin and naringin was found bound to the food matrix by ether/ester bonds. Violaxanthin and β-cryptoxanthin were found as major carotenoids in the orange and mandarin decoction by-products, respectively, whereas the grapefruit decoction by-product showed a low content of carotenoids. All citrus by-products showed β-sitosterol as the major phytosterol, followed by β-campesterol. Therefore, the by-products obtained during the elaboration of citrus decoctions are rich sources of bioactive compounds that can be used for the development of functional foods or dietary supplements.

Optimization and identification of non-extractable polyphenols in the dietary fiber of jackfruit (Artocarpus heterophyllus Lam.) pulp released by alkaline, acid and enzymatic hydrolysis: Content, composition and antioxidant activities

The study presented the first comparison of content and composition along with the antioxidant activities of non-extractable polyphenols (NEPP) in the dietary fiber of jackfruit pulp (JDF) released by alkaline, acid and enzymatic hydrolysis. Firstly, the NEPP extraction was optimized by response surface methodology (RSM), and the alkaline hydrolysis extract contained the most abundant content. Besides, the composition of extracts were characterized by UPLC-ESI-QTOF-MS/MS and the alkaline hydrolysis extract possessed most diverse NEPP (4 phenolic acids and 13 flavonoids). Moreover, the antioxidant activities of NEPP were tested by ABTS·+, ORAC and PSC scavenging ability assays, the antioxidant activities of alkaline hydrolysis extract were significantly highest among three extracts. This study provided available evidence for the NEPP released from dietary fiber (DF) by different methods, and revealed alkaline hydrolysis extract promising potential as a natural source of health care products.

In vitro bile acid binding activity and non-extractable polyphenols of dried persimmon and quince fruits

In vitro bile acid binding activity and non-extractable polyphenols of dried persimmon and quince fruits

Enzyme-assisted extraction of bioactive non-extractable polyphenols from sweet cherry (Prunus avium L.) pomace

Sweet cherries processing produces big amounts of wastes mainly constituted by cherry pomace that can be a source of bioactive polyphenols. However, during the extraction process, an important fraction called non-extractable polyphenols (NEPs) remains retained in the extraction residue. This work describes the development of an enzyme-assisted extraction (EAE) method to obtain NEPs from sweet cherry pomace employing three different enzymes. Box-Behnken experimental designs were employed to select the optimal conditions of extraction time, temperature, enzyme concentration, and pH. The total phenolic and proanthocyanidin contents and the antioxidant and antihypertensive capacities were measured. Optimal EAE conditions extracted higher content of proanthocyanidins and with higher bioactivity from extraction residue than alkaline and acid hydrolysis. Moreover, there were higher amounts of bioactive phenolics in the extraction residue than in the sweet cherry pomace extract. The estimation of NEPs molecular weight distribution by HPLC-SEC demonstrated that EAE extracted NEPs with high molecular weight.

Antioxidant and α-glucosidase inhibitory capacity of nonextractable polyphenols in Mopan persimmon.

This study was to evaluate and compare the polyphenols contents, antioxidant capacities, and α‐glucosidase inhibitory abilities of extractable and nonextractable polyphenols (EP and NEP) in Mopan persimmon. The results showed that total phenols content of NEP was 5 times higher than that of EP, and the hydrolyzed NEP compounds displayed higher antioxidant capacity than EP in vitro by DPPH, ORAC assays. Meanwhile, NEP also exhibited inhibition capacity of α‐glucosidase and were higher than that of acarbose. In addition, an in vitro model of gastrointestinal digestion was used for the release of NEP, the polyphenols content and ORAC values were obviously increased in gastric digestion stage. The result indicated that NEP in Mopan persimmon, which has often been overlooked and discarded in the past, possessed higher polyphenols content and antioxidant capacity than EP.

Non-Extractable Polyphenols from Food By-Products: Current Knowledge on Recovery, Characterisation, and Potential Applications

Non-extractable polyphenols (NEPs), or bound polyphenols, are a significant fraction of polyphenols that are retained in the extraction residues after conventional aqueous organic solvent extraction. They include both high molecular weight polymeric polyphenols and low molecular weight phenolics attached to macromolecules. Current knowledge proved that these bioactive compounds possess high antioxidant, antidiabetic, and other biological activities. Plant-based food by-products, such as peels, pomace, and seeds, possess high amount of NEPs. The recovery of these valuable compounds is considered an effective way to recycle food by-products and mitigate pollution, bad manufacturing practice, and economic loss caused by the residues management. The current challenge to valorise NEPs from plant-based by-products is to increase the extraction efficiency with proper techniques, choose appropriate characterising methods, and explore potential functions to use in some products. Based on this scenario, the present review aims to summarise the extraction procedure and technologies applied to recover NEPs from plant-based by-products. Furthermore, it also describes the main techniques used for the characterisation of NEPs and outlines their potential food, pharmaceutical, nutraceutical, and cosmetic applications.

New players in the relationship between diet and microbiota: the role of macromolecular antioxidant polyphenols.

Solid evidence has emerged supporting the role of polyphenols and fibers as gut microbiota modulators. These studies have been limited to the data available in food composition databases, which did not include the food content of non-extractable polyphenols (NEPP). The main objective of this work is to quantify the intake of the different types of dietary polyphenols including NEPP and to evaluate their impact on the composition and activity of the intestinal microbiota. Cross-sectional descriptive study conducted on a sample of 147 adults with no declared pathologies. Dietary intake has been registered by a semi-quantitative Food Frequency Questionnaire (FFQ) and transformed into extractable (EPP) and NEPP, and dietary fibers based on available databases. Major phylogenetic types of the intestinal microbiota were determined by qPCR and fecal SCFA quantification was performed by gas chromatography. NEPP account for two-thirds of the total polyphenols intake. A combined analysis by stepwise regression model including all dietary fiber and (poly)phenols has identified hydrolysable (poly)phenol (HPP) intake, as the best predictor of Bacteroides-Prevotella-Porphyromonas group and Bifidobacterium levels in feces. Also, HPPs were positively associated with butyric acid, while insoluble fiber was identified as a predictor of propionic acid in feces. The intake of macromolecular (poly)phenols could contribute to modulate the gut microbiota by increasing the levels of certain intestinal microorganisms with proven health benefits.

Chemical profile and antioxidant potential of extractable and non‐extractable polyphenols in commercial teas at different fermentation degrees

The present study aimed to compare the chemical and antioxidant differences between the extractable and non-extractable polyphenols (EPP and NEPP) in commercial teas with different fermentation degrees. The results showed that both content and antioxidant activity of NEPP were lower than EPP regardless of fermentation degrees of teas. One white tea, Baekho Silver Needle (BSN), had the highest NEPP content (58.38 ± 0.73 mg GAE/g DW) by alkaline hydrolysis, as well as the antioxidant activities among different teas studied. Meanwhile, alkaline hydrolysis also was the most effective method in extracting the NEPP from these teas, followed by acid and enzymatic hydrolysis. Combined principle component analysis and hierarchical clustering analysis demonstrated that gallic acid (GA), epigallocatechin (EGC), and gallocatechin (GC) were three major components in the NEEP studied, with the highest content 13.89 ± 0.87 mg/g DW in BSN, 16.14 ± 1.24 mg/g DW in Dianhong (DH), and 7.26 ± 0.55 mg/g DW in Biluochun (BLC), respectively. GA also was found to be the main contributor to antioxidant activity of NEPP. In addition, NEPP with different fermentation degrees showed discriminations in total polyphenols content, phytochemical profiles, and antioxidant activities but were disorder with the fermentation degrees of these teas. These results provided more information for NEPP in teas with different fermentation degrees including the phytochemical profiles and optimal extraction method. Practical applications NEPP have long been underestimated or neglected because this part of polyphenolic fraction cannot be extracted from the residues by aqueous or organic solvents. This study systematically investigated phytochemical profiles and antioxidant activity of EPP and NEPP in commercial teas with different fermentation degrees. Comparing the release efficacy of tea NEPP by different extraction methods indicated that tea residues were still a considerable source for NEPP. Profiles of polyphenols in teas with different fermentation degrees can be better uncovered according to this study to improve the health.

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.

Micronization and granulometric fractionation improve polyphenol content and antioxidant capacity of olive pomace

This study was aimed to evaluate the effect of micronization of granulometrically fractioned olive pomace (OP) on the content of extractable polyphenols (EPP), non-extractable polyphenols (NEPP) and its antioxidant capacity. Crude OP was separated in 2-mm sieve, resulting in two fractions: F1 (> 2 mm) and F2 (< 2 mm). F2 had higher content of ash, fat, soluble dietary fiber, EPP, hydrolyzable tannins (HT) and condensed tannins (CT) than F1. F1 and F2 fractions were defatted and submitted to a micronization process using a factorial design 22 (variables: rotational speed and milling time) with EPP as response. The optimal micronizing conditions, 500 rpm/24.8 min for the F1 and 500 rpm/16 min for the F2, reduced particle size to around 30 μm. Micronization increased the content of EPP and HT in F1 and F2. Granulometric fractionation and micronization were effective to increase EPP content and antioxidant capacity of OP.

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.

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.

Changes in Extractable and Non-extractable Polyphenols and Their Antioxidant Properties during Fruit On-tree Ripening in Five Peach Cultivars

To evaluate the changes of total phenolic content and antioxidant capacities of five peach cultivars, this work measured them separately in extractable polyphenols and non-extractable polyphenols during the last month of ripening. Total phenolic content was detected using the Folin-Ciocalteau reagent, while total antioxidant activity was detected by DPPH and FRAP assay. In addition, the contribution of extractable polyphenols and non-extractable polyphenols to the total antioxidant activity of peaches was investigated. It is noted that ripening caused a decrease of total phenolic content associated to extractable polyphenols and non-extractable polyphenols by 45.1%–74.6%, 20.7%–41.7%, respectively. Additionally, total antioxidant activity decreased over the ripening period with a high correlation with total phenolic content. Extractable polyphenols contributed more than 50% to the total antioxidant activity, while the non-extractable antioxidants contributed around 31.3%–45.7% (DPPH) or 12.6%–25.4% (FRAP), which suggests that the antioxidant properties of peaches may be undervalued in previous researches.

Multivariate Analysis Illuminates the Effects of Vacuum Drying on the Extractable and Nonextractable Polyphenols Profile of Loquat Fruit.

The current study evaluated the effects of vacuum drying on the whole polyphenol profile of loquat fruit, including extractive and nonextractive polyphenols. Absorbance analysis determined that total polyphenol content and antioxidant levels were higher in loquat fruit vacuum dried at 140 °C than in loquat fruit vacuum dried at 70 °C. The results of ultra-HPLC-triple quadruple mass spectrum analysis showed that 15 phenolic acids and 17 flavonoids were found in dried loquat fruit. Multivariate integrative (MINT) sparse partial least square-discriminant analysis showed that vacuum drying affects the polyphenol profile of loquat fruit. Co-analysis of principal component analysis, partial least square-discriminant analysis, and orthometric partial least square-discriminant analysis revealed that vacuum drying mainly changed the content of chlorogenic acid, cryptochlorogenic acid, protocatechuic acid, phloretin, and hesperidin in loquat fruit. Chlorogenic acid (12.020 to 39.153 µg/g d.b. [dried base weight]), the main polyphenol in dried loquat fruit, was degraded to caffeic acid (0.028 to 2.365 µg/g d.b.) and protocatechuic acid (0.014 to 18.285 µg/g d.b.) during vacuum drying. Moreover, vacuum drying also induced the isomerization of chlorogenic acid into cryptochlorogenic acid (1.628 to 12.737 µg/g d.b.). These results might be used to develop dried loquat fruit with high levels of polyphenols and antioxidant activity. PRACTICAL APPLICATION: Interests in polyphenols of loquat fruit had increased greatly because of their possible role in health benefits. This work provided a holistic insight in the effects of vacuum drying on polyphenols profile of loquat fruit. Current results have contributed to the development of vacuum-drying method, which produced loquat fruit rich in polyphenols. Furthermore, it also suggested that multivariate analysis was a feasible method to reveal the important changes of polyphenols profile during food processing.

Non-extractable polyphenols from cranberries: potential anti-inflammation and anti-colon-cancer agents.

Cranberries (Vaccinium macrocarpon) are full of polyphenols, which display various health benefits. Most studies have focused on extractable polyphenols (EPs) rather than non-extractable polyphenols (NEPs) but NEPs may possess important biological functions. The objective of this work was to characterize EP and NEP fractions from whole cranberries and determine their potential as anti-inflammation and anti-colon-cancer agents. Our results showed that of the identified polyphenols, anthocyanins were the major ones in the cranberry EP fraction, while phenolic acids were most abundant in the NEP fraction. The oxygen radical absorbance capacity (ORAC) of the NEPs was significantly higher than that of the EPs. Both the EPs and NEPs showed anti-inflammatory effects in inhibiting LPS-induced production of nitric oxide in macrophages. At the concentrations tested, the NEPs showed significantly higher inhibition of the production of nitric oxide in macrophages than the EPs, which was accompanied by decreased expression of inducible nitric oxide synthase (iNOS) and increased expression of HO-1. EP and NEP samples showed anti-cancer capacities in HCT116 cells. And the NEPs showed stronger inhibitory effects on the viability and colony formation capacity of human colon cancer HCT116 cells than the EPs. In a flow cytometry analysis, the NEPs caused cell cycle arrest at the G0/G1 phase and induced significant cellular apoptosis in colon cancer cells. Overall, our results suggested that both the EP and NEP fractions from cranberries were bioactive, and importantly, the NEP fraction showed promising anti-inflammation and anti-colon-cancer potential.

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.