Degree Of Galloylation Research Articles

The occurring of astringency during persimmon pulp drying and its correlation with tannin derivatives

Drying persimmon pulp causes an increase in astringency, which is a great concern for persimmon manufacturers. This research investigates the increment in astringency observed during three drying technologies, freeze, vacuum and hot air drying, respectively, and proposes two mitigation pretreatments. The phenols in persimmon samples were correlated with their astringent level measured by tannin content, mean degree of polymerization (mDP) and degree of galloylation (DG). The astringency of fresh persimmon pulp increased four times after freeze drying, which is the least compared to hot air and vacuum drying. However, pH adjustment and pectinase hydrolysis can effectively mitigate the astringent taste. The best pre-treatment was pectinase hydrolysis since it decreased the mDP to 4.7 and DG to 13 %, similar to the level of fresh pulp. The acidic pH treatment (pH=2) can also significantly decrease the astringent level, however, the taste perception also changed dramatically. An HPLC-MS-DAD analysis has identified and quantified the phenol profile of dried persimmon, and the concentration of small molecular weight phenols was negatively correlated to the tannin content, thus astringent level. A further multivariate analysis including tannin concentration, phenols quantification and taste simulation by e-tongue confirmed that pectinase pretreatment has the least increment in astringency and similar taste perception.

Development of a cell-based quaternary system to unveil the effect of pectic polysaccharides on oral astringency

Phenolic compounds are responsible for food unpleasant taste properties, including astringency, due to their ability to interact with salivary proteins and oral constituents. Astringency is a crucial attribute for consumer's acceptability. To fulfill the demand for both healthy and tasty food, polysaccharides raise as a good alternative to modulate astringency. In this work, a cell-based quaternary system was developed to evaluate the ability of polysaccharides to reduce the interaction between two classes of hydrolysable tannins – gallotannins (tannic acid) and ellagitannins (punicalagin) – and oral constituents (cells, salivary proteins and mucosal pellicle). So, pectic polysaccharide fractions isolated from grape skins, imidazole soluble polysaccharides (ISP) and carbonate soluble polysaccharides (CSP), as well as a commercial pectin, were tested.Results showed that the polysaccharide's effect depends on the structural features of the molecules involved. CSP fraction and pectin were the most effective, reducing the interactions between both tannins and the oral constituents, mainly in the complete oral model. The highest uronic acid content and the presence of methyl esterified groups could explain their high reduction ability. For tannic acid, the reduction effect increased along with the galloylation degree, while the interaction of β-punicalagin with the oral constituents was practically inhibited at 3.0 mg.mL−1.

New insights into the oral interactions of different families of phenolic compounds: Deepening the astringency mouthfeels

Astringency is a tactile sensation of puckering, tightening and dryness in the oral cavity, commonly induced by polyphenols. In this study, the interaction of two phenolic compound mixtures, one rich in gallotannins and the other in flavonols, with two oral models (tongue (HSC3) or buccal mucosa (TR146) was evaluated. Results provided evidence that gallotannins and flavonols seem to bind in a different way to the different oral constituents and models used. Gallotannins seems to bind more to the tongue than to the buccal mucosa cell line, but this difference is overcome by the presence of salivary proteins. Conversely, for the flavonol mixture, the presence of salivary proteins seems to restrain the interaction with oral cell lines. Structure–binding activity relationships were evidenced within each mixture: for gallotannins, interactions seem to increase along with the galloylation degree while for flavonol it was observed that increasing numbers of glucose residues decreased the binding activity.

Galloyl Group in B-type Proanthocyanidin Dimers Was Responsible for Its Differential Inhibitory Activity on 3T3-L1 Preadipocytes due to the Strong Lipid Raft-Perturbing Potency.

The effects of three B-type proanthocyanidin (PA) dimers covering procyanidin B2 (B-0g), procyanidin B2 3'-O-gallate (B-1g), and procyanidin B2 3,3'-di-O-gallate (B-2g) on 3T3-L1 preadipocyte differentiation and the underlying mechanisms were investigated. The results showed that digalloylated B-type PA dimers (B-2g) strongly inhibited 3T3-L1 preadipocyte differentiation through disrupting the integrity of the lipid raft structure and inhibiting the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα) and then downregulating the expression of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) factors, followed by B-1g, while B-0g had little effect. The different inhibitory effects were mainly due to the difference in the B-type PA dimer structure and the ability to interfere with lipid rafts. The greater the galloylation degree of B-type PA dimers, the stronger the ability to disrupt the lipid raft structure and oppose 3T3-L1 preadipocyte differentiation. In addition, galloylated B-type PA dimers had greater molecular hydrophobicity and topological polarity surface area and could penetrate into the lipid rafts to form multiple hydrogen bonds with the rafts by molecular dynamics simulation. These findings highlighted that the strong lipid raft-perturbing potency of galloylated B-type PA dimers was responsible for inhibition of 3T3-L1 preadipocyte differentiation.

Managing moderate water deficit increased anthocyanin concentration and proanthocyanidin galloylation in “Refošk” grapes in Northeast Italy

Grapevines in Karst between Italy and Slovenia are grown on a shallow "Terrarossa” red karst loam laying on carbonate rocks. In Karst, water stress conditions occur during the summer season both because of the rain scarcity and the poor available water content of the soils. Moreover, irrigation can be used to only partially supply grapevine requirements, where possible. An irrigation trial was carried out in a vineyard of “Refošk” during the seasons 2018–2019 to understand the effects of two deficit irrigation regimes (20% and 50% ETC) on yield parameters and basic maturation, but mainly on polyphenol content, composition and extractability. During the summer season Ψstem was regularly checked in order to follow the plant water status, and at harvest time berry samples were collected to determine the total concentration of anthocyanins and proanthocyanidins and their extractability in a wine-like solution. Moreover, the structural characteristics of seed and skin proanthocyanidins were analyzed. In both seasons, differences in plant water status were ascertained, but values of Ψstem never highlighted situations of severe water stress for both deficit irrigation regimes. 20% ETC resulted in a significant increase in the concentration of both total and extractable anthocyanins; on the other hand, proanthocyanidin concentration was not significantly affected by the irrigation regime. As regards the structure of proanthocyanidins, 20% ETC accounted for a higher degree of galloylation in both total and extractable seed and skin proanthocyanidins. A more limited irrigation regime resulted in both higher anthocyanin concentration and degree of galloylation of seed and skin proanthocyanidins - attributes that might account for a better wine quality potential.

Condensed tannins in the pericarp of diverse Vitis species

Grape condensed tannins (proanthocyanidins) are phenolic substances of utmost importance in the sensory characteristics of wine. Not only does their final concentration affect the fermentation process, but their structure also greatly influences the negative attribute of astringency. Determining the exact amount of proanthocyanidins in the grape pericarp is a real challenge, and a prerequisite in any breeding research program aimed at the improvement of the quality of grape berry tannins. We analyzed pericarp condensed tannins in four species of Asian and American wild grape vines in comparison with four accessions of the domestic grape vine, Vitis vinifera. The mass of tannins per berry ranged from 0.1 to 1.2% FW; however, the relative mole percentage of epigallocatechin in Asian species was 10 times lower than in American species and the domestic grape vine, while the tannin galloylation degree of American vines was 4 and 10 times higher than in domestic and Asian vines, respectively.

Separation, Identification, and Bioactivities of the Main Gallotannins of Red Sword Bean (Canavalia gladiata) Coats.

The red sword bean (Canavalia gladiata) is an underutilized edible bean cultivated in China. It was previously found to have the highest content of antioxidant polyphenols among 42 edible beans, mainly gallic acid, and gallotannins in its red bean coat, an apparently unique characteristic among edible beans. In this study, the main phenolic compounds in red sword bean coats were further separated by Sephadex LH-20 column chromatography, and identified by LC-MS/MS. Furthermore, the FRAP and ABTS antioxidant activities and antibacterial activity (diameter of inhibition zone, DIZ) of main gallotannin-rich fractions were tested. Our results showed that gallotannins of red sword bean coats were mainly comprised of monogalloyl to hexagalloyl hexosides. Interestingly, tetragalloyl, pentagalloyl, and hexagalloyl hexosides were identified as the possible candidates responsible for the red color of the coats. On the other hand, gallotannin-rich fractions exhibited diverse antioxidant and antibacterial activities, and tetragalloyl hexoside overall had the highest free radical scavenging and antibacterial activities. The degree of galloylation did not completely explain the structure-function relationship of gallotannins isolated from red sword bean coats, as there should exist other factors affecting their bioactivities. In conclusion, red sword bean coats are excellent natural sources of gallotannins, and their gallotannin-rich extracts can be utilized as natural antioxidant and antibacterial agents with potential health benefits as well as application in food industry.

New insight into the unresolved HPLC broad peak of Cabernet Sauvignon grape seed polymeric tannins by combining CPC and Q-ToF approaches

Polymeric tannins from grapes have always been reported as an unresolved broad peak in HPLC chromatograms, and this has severely limited their identification to date. This study aimed to disassemble this broad peak and explore the polymeric tannin molecules inside. By applying centrifugal partition chromatography (CPC), an efficient separation approach was developed to split the broad peak of grape seed tannins into fractions. Then, the fractions were analyzed by Q-ToF (quadrupole time-of-flight mass spectrometry) to determine the corresponding structures of the tannins. The results suggest that grape seed polymeric tannins were eluted consecutively according to their degree of polymerization (DP). Condensed tannins identified in wine grape seed have a range of DP and degree of galloylation (DG) up to 20 and 11, respectively. The molecular mass of the largest molecule detected was 6067. To our knowledge, this is the first report to offer an insight into the broad peak of polymeric tannins found with HPLC and to characterize the tannins with a DP up to 20 as shown by HRMS and MS/MS data.

Influence of early seeds removal on the physicochemical, polyphenolic, aromatic and sensory characteristics of red wines from Gaglioppo cv.

The technique of seeds removal during the fermentative maceration was conceived to limit the extraction of polyphenols from the seeds in order to reduce the natural wine astringency. The influence of this oenological practice on the polyphenolic composition of Gaglioppo wines was studied during three vintages (2010–2012): the wines produced in the presence (WS) or absence (WOS) of seeds were compared for the physicochemical, polyphenolic and volatile composition, as well as for the sensory characteristics. Seeds removal did not cause any important modification in the general physicochemical composition of wines. Regarding polyphenols, no differences in total anthocyanins content were observed between the trials, but a significantly lower total polyphenols content was observed in the WOS wines, regarding in particular total flavonoids, low molecular weight flavans and condensed tannins. Qualitative variations in the composition of condensed tannins were also observed: the WOS wines had a higher mean degree of polymerization (mDP) and a lower galloylation degree. Finally, minor differences in the aromatic profile due to the seeds removal technique were observed between the trials. Despite the important modifications of the polyphenolic composition, the sensory characteristics of the wines, on the whole, were not affected: a significant decrease of the bitter taste in the WOS trial was noticed only in vintage 2010.

Browplasminin, a condensed tannin with anti-plasmin activity isolated from an aqueous extract of Brownea grandiceps Jacq. flowers

Ethnopharmacological relevanceFollowing Venezuelan traditional medicine, females with heavy menstrual blood loss (menorrhagia) drink Brownea grandiceps Jacq. flowers (BG) decoctions to reduce the bleeding. In a previous study, we demonstrated that BG aqueous extract (E) possesses a potent anti-fibrinolytic activity capable of inhibiting plasmin, the main serine-protease that degrades fibrin. It is widely known that plasmin inhibitors are often used as anti-fibrinolytics to reduce bleeding during surgeries with high risk of blood loss such as cardiac, liver, vascular, tooth extraction and large orthopedic procedures, as well as for menorrhagia treatments. The aim of this work was to isolate and characterize from BGE the compound responsible for the reported anti-fibrinolytic activity. Materials and methodsA decoction of BG was prepared; then it was homogenized, centrifuged and lyophilized to obtain BGE. Subsequently the extract was fractionated by gel filtration and reverse phase using HPLC and the active compound was characterized by MALDI-ToF MS. The kinetic parameters of anti-plasmin activity were evaluated by an amidolytic assay using a chromogenic substrate; also the anti-plasmin activity was estimated by fibrin plate method. Data were analyzed by nonparametric statistics. ResultsThe active compound was a condensed tannin denominated Browplasminin, which is capable of inhibiting the plasmin activity in a dose-dependent manner when measured in fibrin plates or by the amidolytic activity method; it also has a minor effect on the FXa activity. However, it does not affect the activity of other serine-proteases such as trypsin, t-PA or u-PA. Browplasminin consists predominately of heteroflavan-3-ols of catechin with B-type linkages, and extents up to heptadecamers (~ 5000Da), with hexose residues attached to the polymer that presents a high degree of galloylation. Its IC50 for plasmin was 47.80μg/mL and for FXa was 237.08μg/mL, while the Ki were 0.76 and 61.61μg/mL for plasmin and FXa, respectively. ConclusionsThe overall outcome of this study suggests that Browplasminin could be responsible for reducing heavy menstrual bleeding in women because its kinetic parameters showed that is a good plasmin inhibitor.

Temperature desynchronizes sugar and organic acid metabolism in ripening grapevine fruits and remodels their transcriptome.

BackgroundFruit composition at harvest is strongly dependent on the temperature during the grapevine developmental cycle. This raises serious concerns regarding the sustainability of viticulture and the socio-economic repercussions of global warming for many regions where the most heat-tolerant varieties are already cultivated. Despite recent progress, the direct and indirect effects of temperature on fruit development are far from being understood. Experimental limitations such as fluctuating environmental conditions, intra-cluster heterogeneity and the annual reproductive cycle introduce unquantifiable biases for gene expression and physiological studies with grapevine. In the present study, DRCF grapevine mutants (microvine) were grown under several temperature regimes in duly-controlled environmental conditions. A singly berry selection increased the accuracy of fruit phenotyping and subsequent gene expression analyses. The physiological and transcriptomic responses of five key stages sampled simultaneously at day and nighttime were studied by RNA-seq analysis.ResultsA total of 674 millions reads were sequenced from all experiments. Analysis of differential expression yielded in a total of 10 788 transcripts modulated by temperature. An acceleration of green berry development under higher temperature was correlated with the induction of several candidate genes linked to cell expansion. High temperatures impaired tannin synthesis and degree of galloylation at the transcriptomic levels. The timing of malate breakdown was delayed to mid-ripening in transgressively cool conditions, revealing unsuspected plasticity of berry primary metabolism. Specific ATPases and malate transporters displayed development and temperature-dependent expression patterns, besides less marked but significant regulation of other genes in the malate pathway.ConclusionThe present study represents, to our knowledge the first abiotic stress study performed on a fleshy fruits model using RNA-seq for transcriptomic analysis. It confirms that a careful stage selection and a rigorous control of environmental conditions are needed to address the long-term plasticity of berry development with respect to temperature. Original results revealed temperature-dependent regulation of key metabolic processes in the elaboration of berry composition. Malate breakdown no longer appears as an integral part of the veraison program, but as possibly triggered by an imbalance in cytoplasmic sugar, when efficient vacuolar storage is set on with ripening, in usual temperature conditions. Furthermore, variations in heat shock responsive genes that will be very valuable for further research on temperature adaptation of plants have been evidenced.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0850-0) contains supplementary material, which is available to authorized users.

Characterization of seed proanthocyanidins of thirty-two red and white hybrid grape varieties

Grape seed extracts are known for their beneficial effects on health and on cardiovascular diseases due to antioxidant activity and the free radical-scavenging properties of proanthocyanidins (PAs). Moreover, grape seed tannins are used in oenology as additives to improve the organoleptic characteristics of wines, and for the clarification of must and wines. PAs in seed extract of 32 hybrid and three V. vinifera grape varieties were characterized by MALDI-TOF mass spectrometry. Signals of 148 compounds were identified as [M+H]+, [M+Na]+ and [M+K]+ adducts of B-type and A-type PAs formed from catechin/epicatechin subunits up to undecamers and with galloylation degree 0-7. The number-average molecular weight (Mn) of the samples, a parameter correlated with the molecular weight of polymers, and the polyphenolic content of extract, were also determined. Profiles of the hybrid grape varieties were compared with those of three V. vinifera samples studied as references. 'Terzi 108-6' showed high content of antioxidant polyphenols and 'Seyve Villard 12-390' higher content of higher oligomers. These two grape varieties are therefore potentially very interesting as sources of antioxidants and tannins for nutraceutical and oenological uses.

RP-HPLC–ESI–QTOF/MS2 based strategy for the comprehensive metabolite profiling of Sclerocarya birrea (marula) bark

In this research, a non-selective extraction procedure followed by a RP-HPLC–ESI–QTOF/MS2 method was applied to evaluate the metabolic profile of these extracts, allowing the identification of a total of 95 compounds belonging to the chemical classes of organic acids, polyphenols, fatty acid derivatives, and others, most of these being identified for the first time in these extracts. These proved far richer in polyphenols, and more specifically in proanthocyanidins. This methodology successfully detected from monomers up to dimers of (epi)catechin, (epi)gallocatechin, and (epi)afzelechin units with one or two galloyl residues. A very high degree of galloylation was found, which may serve in the bioactivity attributed to these extracts. The chromatographic method had sufficient resolving power to separate up to six isomeric forms of several compounds, and the structure of some of these isomeric compounds has been elucidated. Therefore, the methodology applied proved useful for the metabolite profiling of Sclerocarya birrea stem–bark extracts, providing essential information that could be used to explain the plethora of ethnotherapeutic properties and pharmacological actions that have been attributed to this African tree.

Comparison of the degradation kinetics of A-type and B-type proanthocyanidins dimers as a function of pH and temperature

The degradation behaviors of four different proanthocyanidins dimers including B-type (e)picatechin (E)C dimer and A-type (epi)catechin (E)C dimer, A-type (epi)catechin-3-O-gallate (E)CG dimer and A-type (epi)gallocatechin-3-O-gallate (E)GCG dimer as affected by pH and temperature were compared in this study. The results showed that the stability of proanthocyanidins dimers was not only temperature and pH dependent, but also structure dependent. Proanthocyanidins dimers were found to be unstable at pH as low as 1.5 and physiological pH conditions, and they were rather unstable at alkaline conditions and temperature above 25 °C. Among the four dimers tested, B-type (E)C dimer was the least stable, while A-type (E)C dimer was the most stable. In general, B-type dimers showed less stability than A-type ones. The higher the degree of galloylation and the more the hydroxyl groups in the molecular, the less stable the proanthocyanidins dimers.

Characterization of phenolic compounds in Brazilian pepper (Schinus terebinthifolius Raddi) exocarp.

The objective of this study was to characterize the phenolic composition of Brazilian pepper (Schinus terebinthifolius Raddi) exocarp extract. Using UHPLC-DAD-MS/MS analysis, four anthocyanins, three biflavonoids, gallic acid, and two types of hydrolyzable tannins (galloyl glucoses, galloyl shikimic acids) were tentatively identified. The structure of the so far unknown 7-O-methylpelargonidin 3-O-β-D-galactopyranoside was elucidated by 2D NMR. Within the group of gallotannins, galloyl shikimic acids with uncommon degrees of galloylation (tetra- to hexagalloyl shikimic acids) were detected. Among the biflavonoids, I3',II8-biapigenin (amentoflavone), I6,II8-biapigenin (agathisflavone), and II-2,3-dihydro-I3',II8-biapigenin were identified, which have already been described for Anacardiaceae. From the results of the present study together with previous findings on the phenolic profile of other Anacardiaceae plants, it is concluded that 7-methoxylated flavonoids are a chemotaxonomic trait frequently found in this family.

Two Galloylated Flavonoids as Antioxidants in Rosa gallica Petals

MCl gel eluted with the solvent system H 2 O–MeOH–acetone, and five fractions were obtained. The fractions obtained by stepwise gradient with H 2 O–MeOH contained flavones with different degrees of galloylation. Fractions 1 and 2 eluted with 90 and 80% H 2 O, respectively, contain two galloylated flavonoids (compounds 1 and 2, respectively) and were isolated by repeated chromatography on Sephadex LH-20 and on a reversed phase column using Wakosil 40C 18 . In the 1 H NMR spectrum of compound 1, two meta-coupled signals were observed at 6.15 and 6.32, and three signals due to 1,3,4-trisubstituted benzene ring protons at 7.56, 7.51, and 6.82. Moreover, an anomeric proton of a sugar moiety was observed at 5.73 (d, J = 7.9) together with six signals of sugar protons at 5.11–3.33, and the coupling constants of these signals indicated the presence of glucose. The specific optical rotation of 1 also indicated the presence of the -D-glucosyl moiety. In the 1 H– 1 H COSY spectrum, the cross peaks of sugar protons were confirmed, but the signal of the H-2 proton of the glucosyl moiety was observed down field at 5.11. This indicated that the hydroxyl group at the C-2 position of glucose was acylated. The molecular weight of compound 1 and the signal of two proton singlets at 7.12 implied the presence of the galloyl group at C-2 of glucose. The signals at 167.8, 146.3, 139.2, 121.0, and 110.6 in the 13 C NMR spectrum also supported the presence of a galloyl group. These data indicated the presence of quercetin [3], the glycosyl unit [4], and the galloyl group. In the HMBC spectrum, H-1 ( 5.73) of the glycosyl moiety showed a correlation with the signal of C-3 ( 134.9) of quercetin. The carbonyl carbon ( 167.8) of the galloyl moiety also showed correlations with H-2 ( 5.11) and H-2 (7.12). Comparing these data with the literature [5, 6], we characterize compound 1 as quercetin 3-O-(2-O-galloyl)-D-glucoside. Compound 2 showed 1 H MNR spectral data similar to those of compound 1, except for the ortho-coupled two proton signals at 7.95 and 6.89 instead of the signals of 1,3,4-trisubstituted benzene. These data indicated the presence of kaempferol as aglycone. Comparing the 1 H and 13 C NMR data and the specific optical rotation with those in the literature [6], we characterize compound 2 as kaempferol 3-O-(2-O-galloyl)--D-glucoside. The two galloylated flavonoids have been isolated from Diospyros kaki Thunb., Geranium tuberosum subsp. tuberosum and Polygonum lapathifolium L. [7–9], but this is the first report on the isolation of these compounds from the plant belonging to the genus Rosa.

Toward Unraveling Grape Tannin Composition: Application of Online Hydrophilic Interaction Chromatography × Reversed-Phase Liquid Chromatography–Time-of-Flight Mass Spectrometry for Grape Seed Analysis

Despite the significant importance of tannins in viticulture and enology, relatively little is known about the detailed chemical composition of these molecules. This is due to challenges associated with the accurate analytical determination of the highly structurally diverse proanthocyanidins which comprise tannins. In this contribution, we address this limitation by demonstrating how online comprehensive two-dimensional liquid chromatography (LC × LC) coupled to high resolution mass spectrometry (HR-MS) can be exploited as a powerful analytical approach for the detailed characterization of grape seed tannins. Hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RP-LC) were employed in the two dimensions to provide complementary information in terms of separation according to hydrophilicity and hydrophobicity, respectively. Online coupling of HILIC × RP-LC with fluorescence detection and electrospray ionization MS delivered high resolution analysis in a practical analysis time, while allowing selective detection and facilitating compound identification. Time-of-flight (TOF) MS provided high acquisition rates and sensitivity coupled to accurate mass information, which allowed detection of procyanidins up to a degree of polymerization (DP) of 16 and a degree of galloylation up to 8 in a red grape seed extract. This analytical methodology promises to shed new light on these important grape constituents and potentially on their evolution during wine production.

Compositional and Sensory Characterization of Red Wine Polymers

After isolation from red wine by means of ultrafiltration and gel adsorption chromatography, the composition of the highly astringent tasting high-molecular weight polymers was analyzed by means of HPLC-MS/MS, HPLC-UV/vis, and ion chromatography after thiolytic, alkaline, and acidic depolymerization and, on the basis of the quantitative data obtained as well as model incubation experiments, key structural features of the red wine polymers were proposed. The structural backbone of the polymers seems to be comprised of a procyanidin chain with (-)-epicatechin, (+)-catechin, (-)-epicatechin-3-O-gallate units as extension and terminal units as well as (-)-epigallocatechin as extension units. In addition, acetaldehyde was shown to link different procyanidins at the A-ring via an 1,1-ethylene bridge and anthocyanins and pyranoanthocyanins were found to be linked to the procyanidin backbone via a C-C-linkage at position C(6) or C(8), respectively. Alkaline hydrolysis demonstrated the polymeric procyanidins to be esterified with various organic acids and phenolic acids, respectively. In addition, the major part of the polysaccharides present in the red wine polymeric fraction were found not to be covalently linked to procyanidins. Interestingly, sensory evaluation of individual fractions of the red wine polymers did not show any significant difference in the astringent threshold concentrations, nor in the astringency intensity in supra-threshold concentrations and demonstrated the mean degree of polymerization as well as the galloylation degree not to have an significant influence on the astringency perception.

Influence of winemaking techniques on proanthocyanidin extraction in Monastrell wines from four different areas

The effect of two low pre-fermentative temperature techniques (cold soak and must freezing with dry ice) using two macerating enzymes was studied during the vinification of Monastrell wines from four different areas (Canada del Judio, Canada de Albatana, Montealegre and Chaparral) belonging to two Denomination of Origins (Jumilla and Bullas), to assess their influence on wine proanthocyanidin concentration and composition. When the control wines were compared, Chaparral wine showed the lowest proanthocyanidin content, together with the lowest mDP and the highest degree of galloylation in its proanthocyanidins, suggesting that the most of the proanthocyanidins in wine had been extracted from the grape seeds. However, Canada de Albatana wines showed the highest proanthocyanidin content. Different results were found in the four areas when the oenological treatments were applied to the grapes. In Canada de Albatana wines, no treatment had any effect, while in the case of Montealegre wines, the cold treatments led to a higher proanthocyanidin content compared with the control wines. In Canada del Judio and Chaparral wines, all the treatments increased the proanthocyanidin content, except when galactoside was used in Chaparral wines, when the results were even lower than for the control wines. Discriminant analyses were applied to check whether the different areas influenced the wine proanthocyanidin profile. The results showed a clear separation between the four plots, suggesting that the proanthocyanidin wine composition was related to the zone where grapes were cultivated.

Galloylated Polyphenols as Inhibitors of Hemoglobin-Catalyzed Lipid Oxidation in Fish Muscle

The influence of galloyl residues on the antioxidant mechanism of polyphenols to prevent hemoglobin-promoted lipid oxidation was investigated by using polyphenolic fractions with different degrees of galloylation: nongalloylated structures from pine bark (IVP), medium-galloylated from grape pomace (IVG), and high-galloylated from witch hazel bark (IVH). Hemoglobin (Hb) from the pelagic fish horse mackerel (Trachurus trachurus) was employed as a Hb standard. In vitro experiments showed an important increase in the deoxygenation and autoxidation of horse mackerel Hb at acidic pH values. All polyphenolic fractions significantly reduced the redox stability of Hb in buffer solutions, showing a greater deoxygenation and methemoglobin (metHb) formation in the presence of IVH, followed in decreasing order by IVG and IVP. However, galloylated polyphenols (IVH and IVG) were efficient to inhibit the oxidation of the oxygenated Hb (OxyHb) and the formation of lipid oxidation products in chilled washed fish muscle. This antioxidant activity of galloylated proanthocyanidins showed a positive relationship with the phenolic concentration. Polyphenols devoid of galloyl groups (IVP) were less active to prevent either Hb oxidation or lipid oxidation in fish muscle. The results draw attention to the potential role of galloyl residues to lessen Hb-catalyzed lipid oxidation in muscle and to maintain Hb in reduced and oxygenated states, which exhibit lower pro-oxidant activity as compared to the metHb and deoxyHb species.