Inhibition of adenosine 3',5'-cyclic monophosphate phosphodiesterase by components of Sophora flavescens Aiton.

Abstract
Adenosine 3'',5''-cyclic monophosphate (cAMP) phosphodiesterase inhibitors containing in the roots of Sophora flavescens Aiton were identified as flavonoids, kushenol A (9), kurarinone (5), and kuraridin (22). The structure-inhibitory activity relationships were studied in 30 flavonoids. O-Methylation of a hydroxyl group on an aromatic ring decreased the activity. The prenyl group is important for high inhibitory activity. A kinetic study revealed that non-kurarinone, kurarinol and kuraridin non-competitively inhibit cAMP phosphodiesterase.