title: Structural features of copigmentation of oenin with different polyphenol copigments.
abstract: The copigmentation binding constants (K) for the interaction of different copigments with oenin (major red wine anthocyanin) were determined. All tests were performed in a 12% ethanol citrate buffer solution (0.2 M) at pH 3.5, with an ionic strength adjusted to 0.5 M by the addition of sodium chloride. Over the past years, several copigmentation studies were made and many copigments were tested, but none of them included prodelphinidin B3 or a dimeric-type adduct like oenin-(O)-catechin, probably due to the difficulty in obtaining them. The data yielded from this study allowed concluding that (a) the presence of a pyrogallol group in the B ring of the flavan-3-ol structure slightly increases the copimentation potential and (b) within all copigments tested oenin-(O)-catechin was revealed to be the best. According to computational studies performed on epicatechin/oenin, epigallocatechin/oenin, procyanidin B3/oenin, and oenin-(O)-catechin/oenin complexes, the ΔGbinding energy of the oenin-(O)-catechin/oenin complex is the most negative compared to the other copigmentation complexes, hence being more stable and thermodynamically favored. All structural data show that oenin-(O)-catechin and epigallocatechin are closer to the pigment molecule, which is in accordance with these two copigments having the highest experimental copigmentation binding constants for oenin.
authors.affiliation: Centro de Investigação em Quı́mica, Departamento de Quı́mica e Bioquı́mica, Faculdade de Ciências, Universidade do Porto, Porto, Portugal.
authors.forename: Natércia
authors.initials: N
authors.lastname: Teixeira
authors.forename: Luís
authors.initials: L
authors.lastname: Cruz
authors.forename: Natércia F
authors.initials: NF
authors.lastname: Brás
authors.forename: Nuno
authors.initials: N
authors.lastname: Mateus
authors.forename: Maria João
authors.initials: MJ
authors.lastname: Ramos
authors.forename: Victor
authors.initials: V
authors.lastname: de Freitas
mesh_terms: D000872:Anthocyanins / Q000737:chemistry* / Q000378:metabolism*; D044946:Biflavonoids / Q000737:chemistry / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D010858:Pigmentation; D010860:Pigments, Biological / Q000737:chemistry / Q000378:metabolism; D059808:Polyphenols / Q000737:chemistry* / Q000378:metabolism*; D044945:Proanthocyanidins / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics; D014920:Wine / Q000032:analysis*
chemical_list: D000872:Anthocyanins; D044946:Biflavonoids; D010860:Pigments, Biological; D059808:Polyphenols; D044945:Proanthocyanidins; C479581:procyanidin B3; D002392:Catechin; C057580:gallocatechol