title: New dibenzotropolone derivatives characterized from black tea using LC/MS/MS.
abstract: Theaflavins and thearubigins are major pigments in black tea, and it is generally accepted that they are produced by oxidation of flavan-3-ols (catechins) during tea fermentation. In the course of studies on the oxidation mechanism of tea polyphenols, especially the formation of thearubigins, a method combining the enzymatic synthesis and LC/ESI-MS/MS analysis was developed to search for new higher molecular weight polymers from black tea. Three new dibenzotropolones, theadibenzotropolone A, B, and C, together with one new tribenzotropolone, theatribenzotropolone A, were formed by the reaction of theaflavins and tea catechins with horseradish peroxidase in the presence of H(2)O(2). The structures of these new benzotropolone derivatives were elucidated on the basis of MS and 2D NMR spectroscopic analyses. The existence of these compounds in black tea was characterized by LC/ESI-MS/MS. Theadibenzotropolone A and B were the first benzotropolone-type trimers of catechins found in the black tea extract. The observation that galloyl ester groups of theaflavins can be oxidized to form di- or tri-benzotropolone skeletons strongly implied that this type of oxidation is an important pathway to extend the molecular size of thearubigins.
authors.affiliation: Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, 164 Frelinghuysen Road, Piscataway, NJ 08854-8020, USA. ssang@rci.rutgrs.edu
authors.forename: Shengmin
authors.initials: S
authors.lastname: Sang
authors.forename: Shiying
authors.initials: S
authors.lastname: Tian
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Stark
authors.forename: Chung S
authors.initials: CS
authors.lastname: Yang
authors.forename: Chi-Tang
authors.initials: CT
authors.lastname: Ho
mesh_terms: D044946:Biflavonoids / Q000737:chemistry; D002392:Catechin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D002853:Chromatography, Liquid; D010636:Phenols / Q000737:chemistry; D059808:Polyphenols; D021241:Spectrometry, Mass, Electrospray Ionization; D013662:Tea / Q000737:chemistry*
chemical_list: D044946:Biflavonoids; D010636:Phenols; D059808:Polyphenols; D013662:Tea; C086701:thearubigin; C056068:theaflavin; D002392:Catechin