PLANT POLYPHENOLS - BIOLOGICALLY-ACTIVE COMPOUNDS OR NONSELECTIVE BINDERS TO PROTEIN

Twenty phenolic compounds, representatives of proanthocyanidins and ga llic acid/hexahydroxyldiphenic acid esters of glucose, have been asses sed for their ability to inhibit binding of specific radioligands to 1 6 receptors. The receptors utilized were alpha 1-, alpha 2- and beta-a drenoceptors, adenosine 1, dopamine 1 and 2, muscarinic, Ca2+ channel, sulphonylureas, 5HT1, 5HT1A, 5HT2, histamine 1, benzodiazepine, opiat e and Na+/K(+)ATPase. These phenolic compounds failed to inhibit ligan ds binding to 10 of the receptors under the test conditions. The most susceptible receptors to phenolic binding were beta-adrenergic, 5HT1 a nd opiate. Some of the compounds tested showed selectivity for a singl e or for two receptors. The inhibition of binding of radioligands to r eceptors by the phenolic compounds cannot be explained solely in terms of phenolic-protein binding. The results indicate that the removal of tannins from plant extracts prior to screening for receptor activitie s may result in missing biologically active compounds with specificity of action. Copyright (C) 1997 Elsevier Science Ltd