title: Flavonoids as antagonists at A1 adenosine receptors.
abstract: This study aimed to investigate the potential for flavonoid action at A(1) adenosine receptors in vitro. In a radioligand binding assay for A(1) adenosine receptor occupancy in particulate preparations from guinea-pig cerebral cortex, flavonoids competed in concentration-dependent manners with Hill slopes typically not different from unity. Of the flavonoids tested, quercetin showed highest affinity (pKi value of 5.33). At a concentration of 28 mm, quercetin evoked a rightward shift in the N(6)-cyclopentyladenosine-induced inhibition of electrically evoked contractions of the guinea-pig isolated ileum, allowing the calculation of a pK(i) value of 4.71. These data suggest, therefore, that flavonoids represent an additional dietary source of A(1) adenosine receptor antagonists (beyond the methylxanthines, caffeine and theophylline).
authors.affiliation: Institute of Neuroscience and School of Biomedical Sciences, University of Nottingham Medical School, Nottingham NG7 2UH, UK. Steve.Alexander@nottingham.ac.uk
authors.forename: Stephen P H
authors.initials: SP
authors.lastname: Alexander
mesh_terms: D058916:Adenosine A1 Receptor Antagonists; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D005260:Female; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D011794:Quercetin / Q000737:chemistry / Q000494:pharmacology; D011869:Radioligand Assay; D043682:Receptor, Adenosine A1 / Q000187:drug effects; D013806:Theophylline / Q000737:chemistry / Q000494:pharmacology; D014970:Xanthines / Q000378:metabolism
chemical_list: D058916:Adenosine A1 Receptor Antagonists; D005419:Flavonoids; D043682:Receptor, Adenosine A1; D014970:Xanthines; D011794:Quercetin; C051360:1,3-dipropyl-8-cyclopentylxanthine; D013806:Theophylline