title: Structure Determination of Novel Oxidation Products from Epicatechin: Thearubigin-Like Molecules.
abstract: Following the oxidation of epicatechin (EC), three novel compounds and two known compounds were isolated. The chemical structures of these oxidation products were determined by mass spectrometry (MS) and various nuclear magnetic resonance (NMR) experiments, and the A-ring-B-ring linkage that is characteristic of catechin was found in each molecule. Three compounds showed similar ultraviolet-visible (UV-Vis) spectra to EC, whereas two compounds showed different spectral absorption in the region between 300 and 500 nm. A similar spectrum was obtained for the thearubigin fraction prepared from a black tea infusion. This result suggests that the condensation reaction between the A-ring and B-ring is more important than reaction between B-rings for thearubigin formation.
authors.affiliation: Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. u8121006@edu.gifu-u.ac.jp.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Uchida
authors.affiliation: Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. t8121010@edu.gifu-u.ac.jp.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ogawa
authors.affiliation: Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. e-yanase@gifu-u.ac.jp.
authors.forename: Emiko
authors.initials: E
authors.lastname: Yanase
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D059808:Polyphenols / Q000737:chemistry / Q000302:isolation & purification*; D013662:Tea / Q000737:chemistry
chemical_list: D059808:Polyphenols; D013662:Tea; C086701:thearubigin; D002392:Catechin
keywords: black tea; epicatechin; oxidation; polymeric polyphenol; theaflavine; thearubigin