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