Chemical Study on the Interaction of Polyphenols with Co-existing Proteins

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We recently isolated a large number of tannins from various medicinal plants, and found their various biological activities including anti-virus, host-mediated antitumor activity, and inhibitory effects on several enzymes. Although these activities have often been regarded as the results of unspecific binding activity of polyphenolic compounds with proteins, the strengths of these activities have been found to differ depending on the structure of each polyphenol. In order to elucidate the interaction of polyphenols with co-existing proteins which should be a basis of their activities, we examined the kinetic aspects in the inhibitory effect of polyphenols on xantine oxidase, HIV reverse transcriptase and lipase. These results indicated that polyphenols exhibit the inhibition in a competitive, non-competitive or uncompetitive manner according to the difference of the chemical structure. In addition, the conformational analysis of polyphenols having an open-chain glucose and gluconic acid core in the molecule, which were newly isolated from several plants, gave the interesting findings on the interaction between polyphenols and proteins in the solution.