ADENOSINE-1 ACTIVE LIGANDS - CIRSIMARIN, A FLAVONE GLYCOSIDE FROM MICROTEA-DEBILIS

Several plants collected through different approaches were screened on distinct receptors using ligand-binding studies as bioassay. Extracts of Microtea debilis showed high activity on adenosine A(1) receptors. Bioassay-guided fractionation using ligand-binding studies resulted i n the isolation of an adenosine A(1) active ligand, cirsimarin (cirsim aritin 4'-O-glucoside). GTP did not influence the radioligand inhibiti on curve of cirsimarin, indicating that this compound is acting as an antagonist at the adenosine-A(1) receptors. The use of this plant agai nst ''proteinuria'' in traditional medicine in Suriname (South America ) may be explained by the adenosine A(1) antagonistic action of cirsim arin. A series of flavonoids was tested in the same assay, but they we re less active. No structure-activity relationship could be observed.