title: Characterization of sulfated quercetin and epicatechin metabolites.
abstract: Different monosulfates of quercetin and epicatechin with metabolic interest were obtained by hemisynthesis and characterized regarding their chromatographic behavior and absorption and mass spectra. Three of these compounds were further isolated, and their structures were elucidated by mass spectrometry and (1)H and (13)C nuclear magnetic resonance using one- and two-dimensional techniques (heteronuclear single-quantum coherence and heteronuclear multiple-bond correlation). The calculation of the proton and carbon shifts caused by sulfation allowed for the assignment of the position of the sulfate group in the flavonoids, so that the compounds were identified as quercetin-3'-O-sulfate, quercetin 4'-O-sulfate, and epicatechin 4'-O-sulfate. It was found that sulfation at position 3' induced a large upfield shift in the carbon bearing the sulfate group and downfield displacements of the adjacent carbons, whereas no significant upfield or downfield shifts were observed with respect to the parent flavonoid when sulfation was produced at position 4'.
authors.affiliation: Grupo de Investigación en Polifenoles (GIP/USAL), Universidad de Salamanca, Unidad de Nutrición y Bromatología, Facultad de Farmacia, Campus Miguel de Unamuno, Salamanca, Spain.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Dueñas
authors.forename: Susana
authors.initials: S
authors.lastname: González-Manzano
authors.forename: Felipe
authors.initials: F
authors.lastname: Surco-Laos
authors.forename: Ana
authors.initials: A
authors.lastname: González-Paramas
authors.forename: Celestino
authors.initials: C
authors.lastname: Santos-Buelga
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D011794:Quercetin / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D013431:Sulfates / Q000737:chemistry / Q000378:metabolism*; D013463:Sulfuric Acid Esters / Q000032:analysis / Q000737:chemistry
chemical_list: D013431:Sulfates; D013463:Sulfuric Acid Esters; C452422:epicatechin sulfate; C531389:quercetin 3'-sulfate; D002392:Catechin; D011794:Quercetin