Plant polyphenols: biologically active compounds or non-selective binders to protein?
Twenty phenolic compounds, representatives of proanthocyanidins and gallic acid/hexahydroxyldiphenic acid esters of glucose, have been assessed for their ability to inhibit binding of specific radioligands to 16 receptors. The receptors utilized were alpha 1-, alpha 2- and beta-adrenoceptors, adenosine 1, dopamine 1 and 2, muscarinic, Ca2+ channel, sulphonylureas, 5HT1, 5HT1A, 5HT2, histamine 1, benzodiazepine, opiate and Na+/K/ATPase. These phenolic compounds failed to inhibit ligands binding to 10 of the receptors under the test conditions. The most susceptible receptors to phenolic binding were beta-adrenergic, 5HT1 and opiate. Some of the compounds tested showed selectivity for a single or for two receptors. The inhibition of binding of radioligands to receptors 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 activities may result in missing biologically active compounds with specificity of action.
Zhu
M
M
Department of Pharmacy, Chinese University of Hong Kong, NT, Hong Kong.
Phillipson
J D
JD
Greengrass
P M
PM
Bowery
N E
NE
Cai
Y
Y
D005419:Flavonoids; D010636:Phenols / Q000378:metabolism / Q000494:pharmacology*; D010944:Plants / Q000737:chemistry*; D011108:Polymers / Q000378:metabolism / Q000494:pharmacology*; D059808:Polyphenols; D011869:Radioligand Assay
D005419:Flavonoids; D010636:Phenols; D011108:Polymers; D059808:Polyphenols