Ellagitannins Renewed the Concept of Tannins

نویسندگان

  • Takuo Okuda
  • Takashi Yoshida
  • Tsutomu Hatano
  • Hideyuki Ito
چکیده

1.1 Old and New Concepts of Tannins The pharmacological activities of tannins described in medicinal books before the recent achievements on ellagitannin chemistry were mostly those of gallotannins and condensed tannins of poor chemical uniformity. The gallotannins extracted from Chinese or Turkish gall, sometimes called tannic acid, are variable mixtures of polygallates of carbohydrates. They cause irritation on skin and mucous membranes, although they have been utilized in some traditional medicinal applications, and are technically defined on the basis of their general capacity to bind to proteins and nitrogen basic compounds such as alkaloids. The condensed tannins, mixtures of oligomeric and polymeric flavanols (e.g., catechins), are chemically more unstable and heterogeneous, thus conforming to the

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تاریخ انتشار 2009