Inhibition of cyclic AMP phosphodiesterase by lignans.

Cyclic adenosine monophosphate (AMP) phosphodiesterase inhibitors contained in Forsythia suspensa were identified as lignans, (+)-pinoresinol (Ja) and (+)-pinoresinol-β-D-glucoside (Id), and their structure-activity relationship was investigated. In pinoresinol congeners, the configuration of the two phenyl rings is very important in relation to the activity. When both of the p-hydroxyl groups in matairesinol congeners are substituted by methyl or glucose, the activities are decreased as compared with those of the unsubstituted compounds.