@article{WieseGaertnerRaweletal.2009,
  author    = {Wiese, Stefanie and Gaertner, Sonja and Rawel, Harshadrai Manilal and Winterhalter, Peter and Kulling, Sabine E.},
  title     = {Protein interactions with cyanidin-3-glucoside and its influence on alpha-amylase activity},
  issn      = {0022-5142},
  doi       = {10.1002/Jsfa.3407},
  year      = {2009},
  abstract  = {BACKGROUND: Recent studies indicate that the bioavailability of anthocyanins is extremely low. One of the possible reasons could be their binding to proteins. Therefore, the binding affinity of cyanidin-3-glucoside (Cy3glc) to HSA and alpha-amylase was investigated by the quenching of protein tryptophan fluorescence. From data obtained, the binding constants and the free Gibbs energy were calculated. The changes in conformation of the proteins tested were studied with circular dichroism and the influence of binding on alpha-amylase activity determined. RESULTS: Cy3glc quenched the tryptophan fluorescence and upon ligand binding a change in protein structure was observed related to the corresponding decrease in the et-amylase activity. The association constants of 25 to 77 x 10(3) L mol(-1) were calculated for different proteins, indicating weak interactions of non-covalent nature. Competitive binding with HSA in the presence of 8-anilino-1-naphthalene sulfonic acid suggest involvement of hydrophobic interactions, in the case of HSA the possible site being subdomain IIA. CONCLUSION: The strongest affinity of Cy3glc for HSA being at pH 7 underlines its potential in transport and distribution of the phenolic compounds in organisms. An influence on salivary amylase activity is possible when drinking berry juices with high anthocyanins content.},
  language  = {en}
}
@article{WeinertWieseRaweletal.2012,
  author    = {Weinert, Christoph H. and Wiese, Stefanie and Rawel, Harshadrai Manilal and Esatbeyoglu, Tuba and Winterhalter, Peter and Homann, Thomas and Kulling, Sabine E.},
  title     = {Methylation of catechins and procyanidins by rat and human Catechol-O-Methyltransferase metabolite profiling and molecular modeling studies},
  series = {Drug metabolism and disposition : the biological fate of chemicals},
  volume    = {40},
  journal   = {Drug metabolism and disposition : the biological fate of chemicals},
  number    = {2},
  publisher = {American Society for Pharmacology and Experimental Therapeutics},
  address   = {Bethesda},
  issn      = {0090-9556},
  doi       = {10.1124/dmd.111.041871},
  pages     = {353 -- 359},
  year      = {2012},
  abstract  = {Catechins and procyanidins are major polyphenols in plant-derived foods. Despite intensive studies in recent years, neither their biochemical nor their toxicological properties have been clarified sufficiently. This study aimed to compare the methylation of catechins and procyanidins by the enzyme catechol-O-methyltransferase (COMT) in vitro. We conducted incubations with rat liver cytosol and human placental cytosol including S-adenosyl-L-methionine. The set of substrates comprised the catechins (-)-epicatechin (EC) and (+)catechin (CAT), the procyanidin dimers B1, B2, B3, B4, B5, and B7 as well as procyanidin trimer C1. After extraction, metabolites were analyzed by means of liquid chromatography-electrospray ionizationmass spectrometry and liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry. EC and CAT were converted to two monomethylated metabolites each by human and rat COMT, with the 3'-O-methyl derivatives being consistently the main metabolites. Furthermore, the flavanyl units of procyanidins were methylated consecutively, leading to monomethylated and dimethylated dimeric metabolites as well as monomethylated, dimethylated, and trimethylated C1 metabolites. The methylation status of each flavanyl unit was determined by means of mass spectrometric quinone-methide fragmentation patterns. In addition, molecular modeling studies were performed with the aim to predict the preferred site of methylation and to verify the experimental data. In conclusion, our results indicate that the degree and position of methylation depend clearly on the three-dimensional structure of the entire substrate molecule.},
  language  = {en}
}
@article{WieseEsatbeyogluWinterhalteretal.2015,
  author    = {Wiese, Stefanie and Esatbeyoglu, Tuba and Winterhalter, Peter and Kruse, Hans-Peter and Winkler, Stephanie and Bub, Achim and Kulling, Sabine E.},
  title     = {Comparative biokinetics and metabolism of pure monomeric, dimeric, and polymeric flavan-3-ols: A randomized cross-over study in humans},
  series = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology},
  volume    = {59},
  journal   = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology},
  number    = {4},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {1613-4125},
  doi       = {10.1002/mnfr.201400422},
  pages     = {610 -- 621},
  year      = {2015},
  abstract  = {Scope: Flavan-3-ols are abundant polyphenols in human nutrition and are associated with beneficial health effects. The aim of this study was to comparatively investigate the metabolic fate of (-)-epicatechin, procyanidin B1, and polymeric procyanidins in a randomized cross-over study in humans. Methods and results: Parent compounds, conjugates, and microbial metabolites were determined in plasma, urine, and faeces by HPLC-MS and GC-MS/MS. Glucuronidated, sulfated, and methylated (-)-epicatechin and 5-(3',4'-dihydroxyphenyl)-valerolactone were the dominant metabolites in blood and urine. In addition, minor amounts of procyanidin B1 and 4-hydroxy-5-(3',4'-dihydroxyphenyl) valeric acid and their conjugated metabolites were detected. The formation of 5-(3',4'-dihydroxyphenyl)-valerolactone and 4-hydroxy-5-(3',4'-dihydroxyphenyl) valeric acid varied largely between individuals as well as with the degree of polymerization of flavan-3-ols. Monomer units were not detectable in plasma or urine after procyanidin B1 and polymeric procyanidin intake. No correlation was found between the intake of flavan-3-ols and the occurrence of phenolic acids in blood and urine or the phenolic compound profiles in faeces. Conclusion: In addition to conjugated metabolites derived from the absorption of monomeric flavan-3-ols, 5-(3',4' -dihydroxyphenyl)-valerolactone represents an important in vivo metabolite of (-)-epicatechin and procyanidin B1 produced by the gut microbiota.},
  language  = {en}
}
@phdthesis{Wiese2010,
  author    = {Wiese, Stefanie},
  title     = {Biokinetik und biologische Aktivit{\"a}t von Flavan-3-olen},
  pages     = {IX, 190, XXI S. : graph. Darst.},
  year      = {2010},
  language  = {de}
}