Inhibition of signal-regulated protein kinases by plant-derived hydrolysable tannins

G. M. Polya, Bing Hui Wang, L. Y. Foo

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61 Citations (Scopus)


A variety of hydrolysable tannins purified from Phyllanthus amarus are potent inhibitors of rat liver cyclic AMP-dependent protein kinase catalytic subunit (cAK) with IC50 values (concentrations for 50% inhibition) in the range 0.2-1.7 μM. The three most effective compounds of this series of hydrolysable tannins have five phenolic substituents. These three compounds are also the most effective inhibitors of wheat embryo Ca2+-dependent protein kinase (CDPK), rat brain Ca2+- and phospholipid-dependent protein kinase C (PKC) and Ca2+-calmodulin-dependent myosin light chain kinase (MLCK). The order of sensitivity for protein kinase inhibition by the hydrolysable tannins studied is cAK>CDPK>PKC>MLCK. Thus the IC50 values for protein kinase inhibition by the most potent compound are 0.2 μM (for cAK), 1.8 μM (for CDPK), 26 μM (for PKC) and 56 μM (for MLCK) when protein kinase affinity is measured using synthetic peptide substrates. These hydrolysable tannin inhibitors found are the most specific and potent plant-derived inhibitors of cAK yet found.

Original languageEnglish
Pages (from-to)307-314
Number of pages8
Issue number2
Publication statusPublished - 1 Jan 1995
Externally publishedYes


  • Euphorbiaceae
  • hydrolysable tannins
  • Phyllanthus amarus
  • protein kinase inhibitors

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