KINASE INHIBITORS FROM POLYGONUM-CUSPIDATUM

Bioassay-directed fractionation of a medicinal plant, Polygonum cuspid atum (Polygonaceae), has led to the discovery of a hydroxystilbene, re sveratrol [1], as an inhibitor of a protein-tyrosine kinase (p56lck) p artially purified from bovine thymus. Both trans and cis isomers of re sveratrol possess comparable protein-tyrosine kinase inhibitory activi ty. Comparison of the IC50 values of resveratrol for protein-tyrosine kinase inhibitory activity with those of piceid (resveratrol-O3-beta-g lucoside) [2) and resveratrol-O4'-beta-glucoside [3] shows the require ment of free hydroxyl groups on both phenyl rings for the protein-tyro sine kinase inhibition. Protein kinase C inhibitory analysis suggests the requirements of two free hydroxyl groups on one phenyl ring only.