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Victor De Freitas - One of the best experts on this subject based on the ideXlab platform.

  • Different Phenolic Compounds Activate Distinct Human Bitter Taste Receptors
    2016
    Co-Authors: Susana Soares, Nuno Mateus, Susann Kohl, Sophie Thalmann, Wolfgang Meyerhof, Victor De Freitas
    Abstract:

    Bitterness is a major sensory attribute of several common foods and beverages rich in polyphenol compounds. These compounds are reported as very important for health as chemopreventive compounds, but they are also known to taste bitter. In this work, the activation of the human bitter taste receptors, TAS2Rs, by six polyphenol compounds was analyzed. The compounds chosen are present in a wide range of plant-derived foods and beverages, namely, red wine, beer, tea, and chocolate. Pentagalloylglucose (PGG) is a hydrolyzable tannin, (−)-epicatechin is a precursor of condensed tannins, Procyanidin Dimer B3 and trimer C2 belong to the condensed tannins, and malvidin-3-glucoside and cyanidin-3-glucoside are anthocyanins. The results show that the different compounds activate different combinations of the ∼25 TAS2Rs. (−)-Epicatechin activated three receptors, TAS2R4, TAS2R5, and TAS2R39, whereas only two receptors, TAS2R5 and TAS2R39, responded to PGG. In contrast, malvidin-3-glucoside and Procyanidin trimer stimulated only one receptor, TAS2R7 and TAS2R5, respectively. Notably, tannins are the first natural agonists found for TAS2R5 that display high potency only toward this receptor. The catechol and/or galloyl groups appear to be important structural determinants that mediate the interaction of these polyphenolic compounds with TAS2R5. Overall, the EC50 values obtained for the different compounds vary 100-fold, with the lowest values for PGG and malvidin-3-glucoside compounds, suggesting that they could be significant polyphenols responsible for the bitterness of fruits, vegetables, and derived products even if they are present in very low concentrations

  • Mechanisms of Tannin-Induced Trypsin Inhibition: A Molecular Approach
    2016
    Co-Authors: Rui Gonçalves, Nuno Mateus, Isabelle Pianet, Michel Laguerre, Victor De Freitas
    Abstract:

    Association of Procyanidins with enzymes has drawn attention over the past few years. This work aimed to bring insights on interaction of the protease trypsin with the Procyanidin Dimer (B3). This interaction was characterized by fluorescence quenching, saturation transfer difference (STD) NMR, molecular modeling, and through an enzymatic inhibition assay. Further studies were conducted regarding the influence of pectin on the binding process. A general overview of the binding process may be outlined as follows: a) at low Procyanidin concentrations (below the critical micellar concentration-(CMC)) a specific interaction probably driven by hydrogen bonds between the protein backbone and the Procyanidin occurs and is associated with the reduction of both enzyme activity and fluorescence; b) at high Procyanidin concentration (above the CMC) the interaction becomes nonspecific. This variation in both nature and extent of the interaction with the variation of Procyanidin concentration shows how tannin self-association may affect the interaction between tannins and proteins. It was also shown that the mechanism through which pectin affects the interaction between Procyanidin B3 and trypsin is of a competitive type

  • Synthesis and structural characterization of oaklin-catechins.
    Journal of agricultural and food chemistry, 2012
    Co-Authors: André M.m. Sousa, Nuno Mateus, Ana Fernandes, Victor De Freitas
    Abstract:

    Condensation reactions of Procyanidin Dimer B4 with two representative oak wood cinnamic aldehydes (coniferaldehyde and sinapaldehyde) were conducted in winelike model solutions. Coniferaldehyde led to the formation of guaiacylcatechin–pyrylium–catechin (GCP–catechin, 737 m/z), whereas sinapaldehyde led to the formation of syringylcatechin–pyrylium–catechin (SCP–catechin, 767 m/z). The former was also structurally characterized by 1D and 2D NMR, allowing an elucidation of the formation mechanism of these oaklin–catechin adducts and demonstrating the importance of Procyanidins in the formation of colored compounds through the reaction with cinnamic aldehydes extracted from oaks during storage.

  • interaction of different polyphenols with bovine serum albumin bsa and human salivary α amylase hsa by fluorescence quenching
    Journal of Agricultural and Food Chemistry, 2007
    Co-Authors: Susana Soares, And Nuno Mateus, Victor De Freitas
    Abstract:

    Phenolic compounds are responsible for major organoleptic characteristics of plant-derived food and beverages; these substances have received much attention, given that the major function of these compounds is their antioxidant ability. In the context of this study, our major aim was study the binding of several phenolic compounds such as (+)-catechin, (−)-epicatechin, (−)-epicatechin gallate, malvidin-3-glucoside, tannic acid, Procyanidin B4, Procyanidin B2 gallate, and Procyanidin oligomers to different proteins (bovine serum albumin and human α-amylase) by fluorescence quenching of protein intrinsic fluorescence. From the spectra obtained, the Stern−Volmer, the apparent static, and the bimolecular quenching constants were calculated. The structure of polyphenols revealed to significantly affect the binding/quenching process; in general, the binding affinity increased with the molecular weight of polyphenol compounds and in the presence of galloyl groups. For catechin monomer and Procyanidin Dimer B4, t...

  • Isolation and structural characterization of new acylated anthocyanin-vinyl-flavanol pigments occurring in aging red wines.
    Journal of agricultural and food chemistry, 2003
    Co-Authors: Nuno Mateus, Celestino Santos-buelga, Elisabete Carvalho, Alexandre R. F. Carvalho, André Melo, Ana M. González-paramás, And Artur M. S. Silva, Victor De Freitas
    Abstract:

    Three newly formed pigments were detected and isolated from a 2-year-old Port wine through TSK Toyopearl HW-40(S) gel column chromatography and characterized by UV−visible spectrophotometry, NMR, and mass spectrometry (ESI/MS). 1H NMR and 13C NMR data for these pigments obtained using 1D and 2D NMR techniques (COSY, NOESY, gHSQC, and gHMBC) are reported for the first time. The structure of the pigments was found to correspond to the vinyl cycloadducts of malvidin 3-coumaroylglucoside bearing either a Procyanidin Dimer or a flavanol monomer ((+)-catechin or (−)-epicatechin). Additionally, conformational analysis was performed for one of these newly formed pigment using computer-assisted model building and molecular mechanics. A chemical nomenclature is proposed to unambiguously name this new family of anthocyanin-derived pigments. Keywords: Red wine; flavanol; aging; pigments; anthocyanins; isomers; NMR; mass spectrometry

Carl L Keen - One of the best experts on this subject based on the ideXlab platform.

  • influence of cocoa flavanols and Procyanidins on free radical induced human erythrocyte hemolysis
    Clinical & Developmental Immunology, 2005
    Co-Authors: Qin Yan Zhu, Heidrun B. Gross, Tomoko Yamaguchi, Derek D Schramm, Roberta R Holt, Sun H Kim, Catherine Kwikuribe, Carl L Keen
    Abstract:

    Cocoa can be a rich source of antioxidants including the flavan-3-ols, epicatechin and catechin, and their oligomers (Procyanidins). While these flavonoids have been reported to reduce the rate of free radical-induced erythrocyte hemolysis in experimental animal models, little is known about their effect on human erythrocyte hemolysis. The major objective of this work was to study the effect of a flavonoid-rich cocoa beverage on the resistance of human erythrocytes to oxidative stress. A second objective was to assess the effects of select purified cocoa flavonoids, epicatechin, catechin, the Procyanidin Dimer B2 and one of its major metabolites, 3'-O-methyl epicatechin, on free radical-induced erythrocyte hemolysis in vitro. Peripheral blood was obtained from 8 healthy subjects before and 1, 2, 4 and 8h after consuming a flavonoid-rich cocoa beverage that provided 0.25g/kg body weight (BW), 0.375 or 0.50g/kg BW of cocoa. Plasma flavanol and Dimer concentrations were determined for each subject. Erythrocyte hemolysis was evaluated using a controlled peroxidation reaction. Epicatechin, catechin, 3'-O-methyl epicatechin and (-)-epicatechin-(4beta > 8)-epicatechin (Dimer B2) were detected in the plasma within 1 h after the consumption of the beverage. The susceptibility of erythrocytes to hemolysis was reduced significantly following the consumption of the beverages. The duration of the lag time, which reflects the capacity of cells to buffer free radicals, was increased. Consistent with the above, the purified flavonoids, epicatechin, catechin, Dimer B2 and the metabolite 3'-O-methyl epicatechin, exhibited dose-dependent protection against AAPH-induced erythrocyte hemolysis at concentrations ranging from 2.5 to 20 microM. Erythrocytes from subjects consuming flavonoid-rich cocoa show reduced susceptibility to free radical-induced hemolysis (p < 0.05).

  • Procyanidin Dimer b2 epicatechin 4β 8 epicatechin in human plasma after the consumption of a flavanol rich cocoa
    The American Journal of Clinical Nutrition, 2002
    Co-Authors: Roberta R Holt, Cesar G. Fraga, Sheryl A Lazarus, John F Hammerstone, Harold H Schmitz, Derek D Schramm, Cameron M Sullards, Carl L Keen
    Abstract:

    Background: Epidemiologic studies have linked flavonoid-rich foods with a reduced risk of cardiovascular mortality. Some cocoas are flavonoid-rich and contain the monomeric flavanols (� )-epicatechin and (+)-catechin and oligomeric Procyanidins formed from these monomeric units. Both the monomers and the oligomers have shown potential in favorably influencing cardiovascular health in in vitro and preliminary clinical studies. Although previous investigations have shown increasing concentrations of (� )-epicatechin in human plasma after cocoa consumption, no information is available in the published literature regarding the presence of Procyanidins in human plasma. Objective: This study sought to determine whether Procyanidins can be detected and quantified in human plasma after acute consumption of a flavanol-rich cocoa. Design: Peripheral blood was obtained from 5 healthy adult subjects before (baseline, 0 h) and 0.5, 2, and 6 h after consumption of 0.375 g cocoa/kg body wt as a beverage. Plasma samples were analyzed for monomers and Procyanidins with the use of reversedphase HPLC with coulometric electrochemical array detection and liquid chromatography‐tandem mass spectrometry. Results: Procyanidin Dimer, (� )-epicatechin, and (+)-catechin were detected in the plasma of human subjects as early as 0.5 h (16 ± 5 nmol/L, 2.61 ± 0.46 � mol/L, and 0.13 ± 0.03 � mol/L, respectively) after acute cocoa consumption and reached maximal concentrations by 2 h (41 ± 4 nmol/L, 5.92 ± 0.60 � mol/L, and 0.16 ± 0.03 � mol/L, respectively). Conclusion: Dimeric Procyanidins can be detected in human plasma as early as 30 min after the consumption of a flavanol-rich food such as cocoa. Am J Clin Nutr 2002;76:798‐804.

Derek D Schramm - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Cocoa Flavanols and Procyanidins on Free Radical-induced Human Erythrocyte Hemolysis
    Clinical & Developmental Immunology, 2005
    Co-Authors: Derek D Schramm, Heidrun B. Gross, Catherine Kwik-uribe, Tomoko Yamaguchi, Roberta R Holt, C L Keen
    Abstract:

    Cocoa can be a rich source of antioxidants including the flavan-3-ols, epicatechin and catechin, and their oligomers (Procyanidins). While these flavonoids have been reported to reduce the rate of free radical-induced erythrocyte hemolysis in experimental animal models, little is known about their effect on human erythrocyte hemolysis. The major objective of this work was to study the effect of a flavonoid-rich cocoa beverage on the resistance of human erythrocytes to oxidative stress. A second objective was to assess the effects of select purified cocoa flavonoids, epicatechin, catechin, the Procyanidin Dimer B2 and one of its major metabolites, 3ʹ-O-methyl epicatechin, on free radical-induced erythrocyte hemolysis in vitro. Peripheral blood was obtained from 8 healthy subjects before and 1, 2, 4 and 8 h after consuming a flavonoid-rich cocoa beverage that provided 0.25 g/kg body weight (BW), 0.375 or 0.50 g/kg BW of cocoa. Plasma flavanol and Dimer concentrations were determined for each subject. Erythrocyte hemolysis was evaluated using a controlled peroxidation reaction. Epicatechin, catechin, 3ʹ-O-methyl epicatechin and (-)-epicatechin-(4β > 8)epicatechin (Dimer B2) were detected in the plasma within 1 h after the consumption of the beverage. The susceptibility of erythrocytes to hemolysis was reduced significantly following the consumption of the beverages. The duration of the lag time, which reflects the capacity of cells to buffer free radicals, was increased. Consistent with the above, the purified flavonoids, epicatechin, catechin, Dimer B2 and the metabolite 3ʹ-O-methyl epicatechin, exhibited dose-dependent protection against AAPH-induced erythrocyte hemolysis at concentrations ranging from 2.5 to 20 μM. Erythrocytes from subjects consuming flavonoid-rich cocoa show reduced susceptibility to free radical-induced hemolysis (p < 0.05).

  • influence of cocoa flavanols and Procyanidins on free radical induced human erythrocyte hemolysis
    Clinical & Developmental Immunology, 2005
    Co-Authors: Qin Yan Zhu, Heidrun B. Gross, Tomoko Yamaguchi, Derek D Schramm, Roberta R Holt, Sun H Kim, Catherine Kwikuribe, Carl L Keen
    Abstract:

    Cocoa can be a rich source of antioxidants including the flavan-3-ols, epicatechin and catechin, and their oligomers (Procyanidins). While these flavonoids have been reported to reduce the rate of free radical-induced erythrocyte hemolysis in experimental animal models, little is known about their effect on human erythrocyte hemolysis. The major objective of this work was to study the effect of a flavonoid-rich cocoa beverage on the resistance of human erythrocytes to oxidative stress. A second objective was to assess the effects of select purified cocoa flavonoids, epicatechin, catechin, the Procyanidin Dimer B2 and one of its major metabolites, 3'-O-methyl epicatechin, on free radical-induced erythrocyte hemolysis in vitro. Peripheral blood was obtained from 8 healthy subjects before and 1, 2, 4 and 8h after consuming a flavonoid-rich cocoa beverage that provided 0.25g/kg body weight (BW), 0.375 or 0.50g/kg BW of cocoa. Plasma flavanol and Dimer concentrations were determined for each subject. Erythrocyte hemolysis was evaluated using a controlled peroxidation reaction. Epicatechin, catechin, 3'-O-methyl epicatechin and (-)-epicatechin-(4beta > 8)-epicatechin (Dimer B2) were detected in the plasma within 1 h after the consumption of the beverage. The susceptibility of erythrocytes to hemolysis was reduced significantly following the consumption of the beverages. The duration of the lag time, which reflects the capacity of cells to buffer free radicals, was increased. Consistent with the above, the purified flavonoids, epicatechin, catechin, Dimer B2 and the metabolite 3'-O-methyl epicatechin, exhibited dose-dependent protection against AAPH-induced erythrocyte hemolysis at concentrations ranging from 2.5 to 20 microM. Erythrocytes from subjects consuming flavonoid-rich cocoa show reduced susceptibility to free radical-induced hemolysis (p < 0.05).

  • Procyanidin Dimer b2 epicatechin 4β 8 epicatechin in human plasma after the consumption of a flavanol rich cocoa
    The American Journal of Clinical Nutrition, 2002
    Co-Authors: Roberta R Holt, Cesar G. Fraga, Sheryl A Lazarus, John F Hammerstone, Harold H Schmitz, Derek D Schramm, Cameron M Sullards, Carl L Keen
    Abstract:

    Background: Epidemiologic studies have linked flavonoid-rich foods with a reduced risk of cardiovascular mortality. Some cocoas are flavonoid-rich and contain the monomeric flavanols (� )-epicatechin and (+)-catechin and oligomeric Procyanidins formed from these monomeric units. Both the monomers and the oligomers have shown potential in favorably influencing cardiovascular health in in vitro and preliminary clinical studies. Although previous investigations have shown increasing concentrations of (� )-epicatechin in human plasma after cocoa consumption, no information is available in the published literature regarding the presence of Procyanidins in human plasma. Objective: This study sought to determine whether Procyanidins can be detected and quantified in human plasma after acute consumption of a flavanol-rich cocoa. Design: Peripheral blood was obtained from 5 healthy adult subjects before (baseline, 0 h) and 0.5, 2, and 6 h after consumption of 0.375 g cocoa/kg body wt as a beverage. Plasma samples were analyzed for monomers and Procyanidins with the use of reversedphase HPLC with coulometric electrochemical array detection and liquid chromatography‐tandem mass spectrometry. Results: Procyanidin Dimer, (� )-epicatechin, and (+)-catechin were detected in the plasma of human subjects as early as 0.5 h (16 ± 5 nmol/L, 2.61 ± 0.46 � mol/L, and 0.13 ± 0.03 � mol/L, respectively) after acute cocoa consumption and reached maximal concentrations by 2 h (41 ± 4 nmol/L, 5.92 ± 0.60 � mol/L, and 0.16 ± 0.03 � mol/L, respectively). Conclusion: Dimeric Procyanidins can be detected in human plasma as early as 30 min after the consumption of a flavanol-rich food such as cocoa. Am J Clin Nutr 2002;76:798‐804.

Chengmei Liu - One of the best experts on this subject based on the ideXlab platform.

  • Protein-polyphenol interactions enhance the antioxidant capacity of phenolics: analysis of rice glutelin-Procyanidin Dimer interactions.
    Food & function, 2019
    Co-Authors: Taotao Dai, Jun Chen, David Julian Mcclements, Chengmei Liu
    Abstract:

    Rice glutelin and Procyanidins are often used in functional foods as sources of plant-based proteins and polyphenols, respectively, but little is currently known about the interactions between them. In our research, the interaction between rice glutelin and the B-type Procyanidin Dimer (PB2) was investigated. The presence of the PB2 decreased the α-helix and random coil structure of the rice protein and reduced its surface hydrophobicity. However, the PB2 did not adversely affect the functional performance of RG in emulsions. Conversely, the antioxidant capacity of the PB2 was enhanced in the presence of the rice protein. Fluorescence spectroscopy confirmed that the protein and PB2 formed molecular complexes, which were primarily the result of hydrophobic attractive forces. Molecular docking analysis provides insights into the nature of the interaction between the rice protein and PB2. This study provides valuable insights into the nature of the interactions between plant proteins and polyphenolic nutraceuticals.

  • Investigation the interaction between Procyanidin Dimer and α-glucosidase: Spectroscopic analyses and molecular docking simulation.
    International journal of biological macromolecules, 2019
    Co-Authors: Taotao Dai, Jun Chen, David Julian Mcclements, Chengmei Liu
    Abstract:

    Procyanidins are reported to inhibit α-glucosidase, which may be a useful attribute for developing functional foods that control post-prandial blood sugar levels. At present, the nature of the molecular interaction between Procyanidins and α-glucosidase is poorly understood. In this study, spectroscopic analyses and computer simulations were used to investigate the interactions between α-glucosidase and B-type Procyanidin Dimer (BPD). Our results suggest that BPD binds to α-glucosidase through a combination of hydrophobic and hydrophilic interactions. This hypothesis was based on measurements of the intrinsic fluorescence quenching, conformational changes, and surface hydrophobicity of the α-glucosidase after binding. Thermodynamic analysis suggested that α-glucosidase had one binding site for BPD and that the interaction was spontaneous. Homologous modeling of α-glucosidase was used to provide information about the precise nature of the molecular interactions. Molecular docking analysis suggested that BPD formed hydrogen bonds and hydrophobic interactions with α-glucosidase when it bound to its active site. This research offers new insights into the mechanism of interaction between Procyanidins and α-glucosidase, which may be useful for the development of functional foods to tackle type 2 diabetes.

  • Investigation the interaction between Procyanidin Dimer and α-amylase: Spectroscopic analyses and molecular docking simulation.
    International journal of biological macromolecules, 2018
    Co-Authors: Taotao Dai, Jun Chen, Chengmei Liu
    Abstract:

    Procyanidins were reported to have an inhibitory effect on α-amylase, but the interaction mechanism between Procyanidins and α-amylase was rarely reported. Spectroscopic and molecular docking techniques were utilized to explore the interaction between porcine pancreatic α-amylase (PPA) and B-type Procyanidin Dimer (PB2). PB2 decreased the intrinsic fluorescence and surface hydrophobicity of PPA, indicating that an interaction occurred and complex formed. The binding process of complex was spontaneous and the main interaction was hydrophobic force. Circular dichroism showed conformational changes of PPA with an increasing of α-helix and β-sheet structure. Molecular docking speculated that PB2 could form hydrophobic force with PPA by bind to the active sit (Asp 167, Asn 100, Arg 158, His 201). This research can offer new insights into the mechanism of PB2 in inhibiting PPA catalysis and provide useful information on dietary recommendation of PB2 for the treatment of type 2 diabetes.

Nuno Mateus - One of the best experts on this subject based on the ideXlab platform.

  • Mechanisms of Tannin-Induced Trypsin Inhibition: A Molecular Approach
    2016
    Co-Authors: Rui Gonçalves, Nuno Mateus, Isabelle Pianet, Michel Laguerre, Victor De Freitas
    Abstract:

    Association of Procyanidins with enzymes has drawn attention over the past few years. This work aimed to bring insights on interaction of the protease trypsin with the Procyanidin Dimer (B3). This interaction was characterized by fluorescence quenching, saturation transfer difference (STD) NMR, molecular modeling, and through an enzymatic inhibition assay. Further studies were conducted regarding the influence of pectin on the binding process. A general overview of the binding process may be outlined as follows: a) at low Procyanidin concentrations (below the critical micellar concentration-(CMC)) a specific interaction probably driven by hydrogen bonds between the protein backbone and the Procyanidin occurs and is associated with the reduction of both enzyme activity and fluorescence; b) at high Procyanidin concentration (above the CMC) the interaction becomes nonspecific. This variation in both nature and extent of the interaction with the variation of Procyanidin concentration shows how tannin self-association may affect the interaction between tannins and proteins. It was also shown that the mechanism through which pectin affects the interaction between Procyanidin B3 and trypsin is of a competitive type

  • Different Phenolic Compounds Activate Distinct Human Bitter Taste Receptors
    2016
    Co-Authors: Susana Soares, Nuno Mateus, Susann Kohl, Sophie Thalmann, Wolfgang Meyerhof, Victor De Freitas
    Abstract:

    Bitterness is a major sensory attribute of several common foods and beverages rich in polyphenol compounds. These compounds are reported as very important for health as chemopreventive compounds, but they are also known to taste bitter. In this work, the activation of the human bitter taste receptors, TAS2Rs, by six polyphenol compounds was analyzed. The compounds chosen are present in a wide range of plant-derived foods and beverages, namely, red wine, beer, tea, and chocolate. Pentagalloylglucose (PGG) is a hydrolyzable tannin, (−)-epicatechin is a precursor of condensed tannins, Procyanidin Dimer B3 and trimer C2 belong to the condensed tannins, and malvidin-3-glucoside and cyanidin-3-glucoside are anthocyanins. The results show that the different compounds activate different combinations of the ∼25 TAS2Rs. (−)-Epicatechin activated three receptors, TAS2R4, TAS2R5, and TAS2R39, whereas only two receptors, TAS2R5 and TAS2R39, responded to PGG. In contrast, malvidin-3-glucoside and Procyanidin trimer stimulated only one receptor, TAS2R7 and TAS2R5, respectively. Notably, tannins are the first natural agonists found for TAS2R5 that display high potency only toward this receptor. The catechol and/or galloyl groups appear to be important structural determinants that mediate the interaction of these polyphenolic compounds with TAS2R5. Overall, the EC50 values obtained for the different compounds vary 100-fold, with the lowest values for PGG and malvidin-3-glucoside compounds, suggesting that they could be significant polyphenols responsible for the bitterness of fruits, vegetables, and derived products even if they are present in very low concentrations

  • Synthesis and structural characterization of oaklin-catechins.
    Journal of agricultural and food chemistry, 2012
    Co-Authors: André M.m. Sousa, Nuno Mateus, Ana Fernandes, Victor De Freitas
    Abstract:

    Condensation reactions of Procyanidin Dimer B4 with two representative oak wood cinnamic aldehydes (coniferaldehyde and sinapaldehyde) were conducted in winelike model solutions. Coniferaldehyde led to the formation of guaiacylcatechin–pyrylium–catechin (GCP–catechin, 737 m/z), whereas sinapaldehyde led to the formation of syringylcatechin–pyrylium–catechin (SCP–catechin, 767 m/z). The former was also structurally characterized by 1D and 2D NMR, allowing an elucidation of the formation mechanism of these oaklin–catechin adducts and demonstrating the importance of Procyanidins in the formation of colored compounds through the reaction with cinnamic aldehydes extracted from oaks during storage.

  • Isolation and structural characterization of new acylated anthocyanin-vinyl-flavanol pigments occurring in aging red wines.
    Journal of agricultural and food chemistry, 2003
    Co-Authors: Nuno Mateus, Celestino Santos-buelga, Elisabete Carvalho, Alexandre R. F. Carvalho, André Melo, Ana M. González-paramás, And Artur M. S. Silva, Victor De Freitas
    Abstract:

    Three newly formed pigments were detected and isolated from a 2-year-old Port wine through TSK Toyopearl HW-40(S) gel column chromatography and characterized by UV−visible spectrophotometry, NMR, and mass spectrometry (ESI/MS). 1H NMR and 13C NMR data for these pigments obtained using 1D and 2D NMR techniques (COSY, NOESY, gHSQC, and gHMBC) are reported for the first time. The structure of the pigments was found to correspond to the vinyl cycloadducts of malvidin 3-coumaroylglucoside bearing either a Procyanidin Dimer or a flavanol monomer ((+)-catechin or (−)-epicatechin). Additionally, conformational analysis was performed for one of these newly formed pigment using computer-assisted model building and molecular mechanics. A chemical nomenclature is proposed to unambiguously name this new family of anthocyanin-derived pigments. Keywords: Red wine; flavanol; aging; pigments; anthocyanins; isomers; NMR; mass spectrometry

  • Identification of anthocyanin-flavanol pigments in red wines by NMR and mass spectrometry.
    Journal of agricultural and food chemistry, 2002
    Co-Authors: Nuno Mateus, Artur M. S. Silva, Celestino Santos-buelga, Julián C. Rivas-gonzalo, Victor De Freitas
    Abstract:

    Three newly formed Port wine pigments were isolated by Toyopearl HW-40(s) gel chromatography and semipreparative HPLC. Furthermore, the pigments were identified by mass spectrometry (LC/MS) and NMR techniques (1D and 2D). These anthocyanin-derived pigments showed UV−visible spectra different from those of the original grape anthocyanins. These pigments correspond to malvidin 3-glucoside linked through a vinyl bond to either (+)-catechin, (−)-epicatechin, or Procyanidin Dimer B3 [(+)-catechin-(+)-catechin]. NMR data of these pigments are reported for the first time. Keywords: Red wine; flavanol; aging; pigments; anthocyanins; NMR; mass spectrometry