Chemical Studies on Plant Polyphenols and Formation of Black Tea Polyphenols

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  • TANAKA Takashi
    Graduate School of Biomedical Sciences, Division of Natural Product Chemistry, Nagasaki University

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  • 植物ポリフェノールに関する化学的研究とその紅茶色素生成機構解明への展開
  • ショクブツ ポリフェノール ニ カンスル カガクテキ ケンキュウ ト ソノ コウチャ シキソ セイセイ キコウ カイメイ エノ テンカイ

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Abstract

  Recent biological and pharmacological studies strongly suggested that plant polyphenols in foods, beverages and crude drugs have various health benefits. However, still there are chemically uncharacterized polyphenols, especially those with large molecular weights. The typical example is black tea polyphenols. Four tea catechins of fresh tea leaves are enzymatically oxidized in tea fermentation process of black tea manufacture to give a complex mixture of the oxidation products. Despite many efforts since 1950's, major part of the black tea polyphenols has not been clarified yet. We have investigated the oxidation mechanism of each catechin by employing a newly developed in vitro model fermentation system. The oxidation was initiated by enzymatic dehydrogenation of catechins, and subsequent intermolecular quinone-phenol coupling reactions followed by cascade-type degradation of the unstable products resulted in the formation of complex black tea polyphenols. Besides black tea polyphenols, this review introduces the chemistry of insolubilization of persimmon proanthocyanidins, wood polyphenols in connection with whisky polyphenols, and co-polymerization of cinnamaldehyde and proanthocyanidins in cinnamon bark.<br>

Journal

  • YAKUGAKU ZASSHI

    YAKUGAKU ZASSHI 128 (8), 1119-1131, 2008-08-01

    The Pharmaceutical Society of Japan

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