title: A new catechin oxidation product and polymeric polyphenols of post-fermented tea.
abstract: A new epicatechin oxidation product with a 3,6-dihydro-6-oxo-2H-pyran-2-carboxylic acid moiety was isolated from a commercially available post-fermented tea that is produced by microbial fermentation of green tea. The structure of this product was determined by spectroscopic methods. A production mechanism that includes the oxygenative cleavage of the catechol B-ring of (-)-epicatechin is proposed. In addition, polymeric polyphenols were separated from the post-fermented tea and partially characterised by (13)C NMR spectroscopy and gel-permeation chromatography. The polymers appear to be primarily composed of epigalloacetechin-3-O-gallate and the molecular weight (Mn) of the acetylated form was estimated to be ∼3500.
authors.affiliation: Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan; Research Center of Tea Processing Engineering, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 Meiling South Road, Hangzhou 310008, Zhejiang, PR China.
authors.forename: He-Yuan
authors.initials: HY
authors.lastname: Jiang
authors.affiliation: Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Shii
authors.affiliation: Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Matsuo
authors.affiliation: Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan. Electronic address: t-tanaka@nagasaki-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, Hong Kong, PR China.
authors.forename: Zhi-Hong
authors.initials: ZH
authors.lastname: Jiang
authors.affiliation: Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo Machi, Nagasaki 852-8521, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Kouno
keywords: Catechin; Oxidation; Polyphenol; Post-fermented tea; Tea