Search

The first contact of polyphenols (tannins) with the human body occurs in the mouth, where they are known to interact with proline‐rich proteins (PRPs). These interactions are important at a sensory level, especially for the development of astringency, but affect also various other biochemical processes. Employing thermodynamic measurements, fluorescence and CD spectroscopy, we investigated the binding process of the prototypical polyphenol ellagic acid (EA) to different IB‐PRPs and BSA, also in the presence of ethanol, which is known to influence tannin–protein interactions. Binding of EA to BSA and the small peptide IB7‐14 is weak, but very strong to IB9‐37. The differences in binding strength and stoichiometry are due to differences in the binding motifs, which also lead to differences in the thermodynamic signatures of the binding process. EA binding to BSA is enthalpy‐driven, whereas binding to both IB7‐14 and IB9‐37 is entropy‐driven. The presence of 10 vol.% EtOH, as present in wines, increases the binding constant of EA with BSA and IB7‐14 drastically, but not that with IB9‐37; however, it changes the binding stoichiometry. These differences can be attributed to the effect of EtOH on the conformation dynamics of the proteins and to changes in hydration properties in alcoholic solution. [ABSTRACT FROM AUTHOR]

This article, titled "Cover Feature: Alcohol-Induced Conformation Changes and Thermodynamic Signatures in the Binding of Polyphenols to Proline-Rich Salivary Proteins," explores the interaction between polyphenols, specifically ellagic acid, and salivary proteins in the mouth. The study found that the presence of ethanol, as found in wines, significantly increases the binding of ellagic acid to salivary proteins. This increase in binding is attributed to the effect of ethanol on the conformational dynamics and hydration of the proteins. For more information, readers can refer to the research article by N. Jahmidi-Azizi, R. Oliva, and R. Winter. [Extracted from the article]

Punicalagin and ellagic acid are the major polyphenols present in pomegranate peels. The contents of α‐punicalagin, β‐punicalagin, and ellagic acid in the pomegranate peels were approximately 75, 72, and 20 µM, respectively. The reactions of polyphenols in pomegranate peels with sodium nitrite under simulated stomach conditions were studied. The reactions decreased the polyphenolic contents of the pomegranate peels and accompanied the formation of nitroso compounds. The oxidation rates followed the order ellagic acid ＜α‐punicalagin ≈ β‐punicalagin. The results suggested that the reactions can occur in the stomach after a meal, while the pH changes from 2 to 4.5. [ABSTRACT FROM AUTHOR]

Abstract: Ellagic acid, a natural polyphenol, was isolated from pomegranate peel extract by hydrophobic interaction using graphene oxide grafted cotton fiber as a stationary adsorbent. The grafted graphene oxide moieties served as hydrophobic interaction‐binding sites for ellagic acid adsorption. The graphene oxide grafted cotton fiber was made into a membrane‐like sheet in order to complete ellagic acid purification by using a binding–elution mode. The effects of operational parameters, such as the composition of the binding buffer/elution buffer, buffer pH, and buffer concentration, on the isolation process were investigated. It was found that 5 mmol/L sodium carbonate aqueous solution is a proper‐binding buffer, and sodium hydroxide aqueous solution ranging from 0.04 to 0.06 mol/L is a suitable elution solution for ellagic acid purification. Under the optimized condition, the purity of ellagic acid increased significantly from 7.5% in the crude extract to 75.0–80.0%. The pH value was found to be a key parameter that determines the adsorption and desorption of ellagic acid. No organic solvent is involved in the entire purification process. Thus, a simple and environmentally friendly method is established for ellagic acid purification using a graphene oxide‐modified biodegradable and bio‐sourced fibrous adsorbent. [ABSTRACT FROM AUTHOR]

The effect of photoperiod on nutritional quality and chemical composition of 'Glen Ample' red raspberry has been studied under controlled environment conditions. Long day (LD) conditions during fruit growth and maturation significantly increased fruit concentrations of ascorbic acid, total phenolics, organic acids such as malic, quinic and ellagic acids, as well as the ferric reducing activity power, while reducing the concentrations of soluble solids, sucrose and the sugar/acid ratio. The levels of total anthocyanin and oxalic acid were not significantly affected by photoperiod whereas semi-quantitative analysis indicated a significant increase in the levels of some ellagitannins. The same responses were found whether LD was established by day-length extension with low-intensity light or by night interruption, thus demonstrating that the observed changes in nutritional quality of raspberry fruit was mediated through specific photoperiodic mechanism(s) independently of the daily light energy supply. [ABSTRACT FROM AUTHOR]

Synopsis Objectives Natural botanical agents that are antimicrobial, or that modulate skin hyperpigmentation via tyrosinase inhibition, are increasingly sought in the cosmetic industry. Methods In this study, an efficient tactic is demonstrated for concentrating and stabilizing skin-beneficial bioactive compounds from muscadine grape and blackcurrant juice or muscadine pomace, into hemp flour ( HF), hemp protein isolate ( HPI) and soy protein isolate ( SPI) matrices suitable for cosmetic applications. Results Anthocyanins were most efficiently captured from blackcurrant juice into HF (8.39 mg g−1). HPI most effectively captured total phenolics from muscadine pomace (72.32 and 77.32 mg g−1 from Noble and Carlos, respectively), while the three matrices incorporated highest levels of ellagic acid, gallic acid, and PAC B1 from Noble muscadine grape juice. The enriched matrices demonstrated effective in vitro inhibition of tyrosinase (up to 57.29% for blackcurrant juice- HPI matrix), and in general, juice sources provided greater inhibition on L-dopamine oxidation by tyrosinase than pomace sources. The polyphenol-enriched matrices effectively inhibited microbial proliferation in a screening assay against Staphylococcus aureus bacteria, whereas untreated HF, HPI or SPI did not inhibit bacterial growth. Conclusion The technology of combining and stably concentrating phytoactive polyphenols with proteins has potential use for cosmetic topical applications. [ABSTRACT FROM AUTHOR]

A rapid and convenient method was established to preparatively isolate the three ellagic acid types of compounds, which were the main polyphenols in Euphorbia pekinensis, by flexibly applying solvent extraction combined with counter-current chromatography ( CCC). The total extract (extracted using 95% ethanol) of E. pekinensis was pretreated by two simple steps before CCC isolation, following the procedure: the total extract was extracted by classical solvent extraction using petroleum ether and ethyl acetate, respectively, and then the ethyl acetate extract was suspended using 95% ethanol, after being allowed to stand overnight, the sediment was obtained. Partial sediment (100 mg) was then directly separated by CCC with a two-phase solvent system composed of chloroform-95% ethanol-water-85% formic acid (50:50:50:5, v/v/v/v). About 22 mg of 3,3′-dimethoxy ellagic acid (1), 12 mg of 3,3′-di- O-methyl-4- O-( β- d-xylopyranosyl)ellagic acid (2), and 35 mg of ellagic acid (3) with purities of 96.0, 95.2, and 95.4% were obtained respectively in one step within 4 h. After being purified by washing with methanol, the purities of the three compounds obtained were all above 98%. The purities were determined by HPLC and their chemical structures were further identified by 1 H and 13 C NMR spectroscopy. The recoveries were calculated as 84.6, 85.7, and 89.5%, respectively. The result demonstrated that the present isolation method was rapid, economical and efficient for the preparative separation of polyphenols from E. pekinensis. [ABSTRACT FROM AUTHOR]

Ellagic acid has been described as an inhibitor of tyrosinase or polyphenol oxidase and, therefore, of melanogenesis. In this work, we demonstrate that ellagic acid is not an inhibitor, but a substrate of mushroom polyphenol oxidase, an enzyme which oxidizes ellagic acid, generating its o-quinone. Because o-quinones are very unstable, we used an oxymetric method to characterize the kinetics of this substrate, based on measurements of the oxygen consumed in the tyrosinase reaction. The catalytic constant is very low at both pH values used in this work (4.5 and 7.0), which means that the Michaelis constant for the oxygen is low. The affinity of the enzyme for the substrate is high (low KmS), showing the double possibility of binding the substrate. Moreover, a new enzymatic method is applied for determining the antioxidant activity. Ellagic acid shows high antioxidant activity (EC50 = 0.05; number of electrons consumed by molecule of antioxidant = 10), probably because of the greater number of hydroxyl groups in its structure capable of sequestering and neutralizing free radicals. © 2008 IUBMB IUBMB Life, 61(2): 171–177, 2009 [ABSTRACT FROM AUTHOR]

Consumption of berries has been implicated with diverse health benefits, such as prevention of stroke, of age-related degenerative diseases and cancer. Some berry constituents have been proven to have cancer preventive actions on chemically induced tumors in vivo and cancer suppressive effects in in vitro studies. Many of these effects were attributed to certain berry phytochemicals with high antioxidative potential that could contribute to, or enhance by induction, the endogenous antioxidant properties of living cells or organisms. Producers and the consumers of berry products need more comprehensive and accurate information on the type and level of health benefits that can be expected from different products. The choice of the chemical or biological test that best predicts specific health benefits of berries is crucial to provide targets for berry breeding programmes or to improve processing methods. The aim of this review is to examine the chemical and biological tests developed to characterize the impact of berries on consumer health. [ABSTRACT FROM AUTHOR]