J Nat Prod. 1997 Jun; 60(6): 638-41.

Adenosine-1 active ligands: cirsimarin, a flavone glycoside from Microtea debilis.

Hasrat JA, Pieters L, Claeys M, Vlietinck A, De Backer JP, Vauquelin G.

Department of Pharmaceutical Sciences, University of Antwerp, Belgium.

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 A1 receptors. Bioassay-guided fractionation using ligand-binding studies resulted in the isolation of an adenosine A1 active ligand, cirsimarin (cirsimaritin 4'-O-glucoside). GTP did not influence the radioligand inhibition curve of cirsimarin, indicating that this compound is acting as an antagonist at the adenosine-A1 receptors. The use of this plant against "proteinuria" in traditional medicine in Suriname (South America) may be explained by the adenosine A1 antagonistic action of cirsimarin. A series of flavonoids was tested in the same assay, but they were less active. No structure-activity relationship could be observed.